Note: Descriptions are shown in the official language in which they were submitted.
CA 02324140 2000-09-15
WO 99/47570 PCT/US99/05940
MACROMOLECULAR SELF-ASSEMBLY OF MICROSTRUCTURES,
NANOSTRUCTURES, OBJECTS, AND MESOPOROUS SOLIDS
This application claims the benefit of U.S. Provisional Patent Application
No. 60/078,473, filed March 18, 1998, which is hereby incorporated by
reference.
FIELD OF THE INVENTION
The present invention relates to microstructures, nanostructures, objects, or
mesoporous soiids formed from rod-coil block copolymers. The present invention
also
relates to methods of making microstructures, nanostructures, objects, or
mesoporous
solids.
BACKGROUND OF THE INVENTION
Development of methods for the preparation and characterization of
robust, functional, structurally well-defined, three-dimensional self
assembled
nanostructures (1-100 nm) and microstructures (102- 10' nm) is considered to
be one of
the "grand challenges now facing chemistry " through the early decades of the
twenty-first
century (Whitesides et al., Science, 254:1312-1319 (1991); Whitesides, Angew.
Chem.
Int. Ed. En~l., 29:1209-1218 (1990)). Such mesostructures (1-10' nm) are of
broad
fundamental and applied interests not only in chemistry but also biology,
physics,
materials science, colloid science, and surface science, while also addressing
societal
concerns in health care, the environment, energy needs, and national security
(Whitesides,
Anew. Chem. Int. Ed. En~l., 29:1209-1218 ( 1990)). The successful development
of the
science and technology of molecular self assembly for producing functional
mesostructures could have a revolutionary impact on the products, product
design, and
manufacturing processes in many industries including those concerned with
food,
pharmaceuticals, cosmetics, biomaterials, lubricants, separation membranes,
adhesives,
thin films, coatings, paints, photographic films, storage and imaging media,
catalysts and
catalyst supports, microfabrication, microelectronics, and nanoscale
electronics and
photonics.
The design and synthesis of self assembling molecules and
macromolecules, construction of diverse, functional, mesostructures (1-10'
run) by self
assembly, and investigation of their functions and properties are among the
central goals
of supramolecular chemistry (Lehn, Supramolecular Chemistry, VCH, Weinheim and
New York ( 1995); Lehn et al., Comprehensive Supramolecular Chemistry,
Pergamon,
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New York, I I vols., ( 1996)). The many advances in the field of
supramolecular
chemistry in the last 20 years have recently been reviewed extensively (Lehn,
Supramolecuiar Chemistry, VCH, Weinheim and New York ( 1995); Lehn et al.,
Comprehensive Supramolecular Chemistry, Pergamon, New York, 1 I vols., (
1996); Conn
et al., Chem. Rev., 97:1647-1668 (1997); Chapman et al., Tetrahedron. 53:15911-
15945
(1997); Fyfe et al., Acc. Chem. Res., 30:393-401 (1997); Ciferri, Prog. Polym
Sci.,
20:1081-1120 (1995)). Although numerous one- and two-dimensional self
assembled
systems are known, reports of three-dimensional (3-D) self assembled
nanostructures
such as capsules, spheres, and nanotubes are fewer, and the size scale of the
largest self
assembled 3-D objects reported to date is only in the few tens of nanometers
(ca. 10-30
nm) (Whitesides et al., Science, 254:1312-1319 (199I); Whitesides, Angew.
Chem. Int.
Ed. En~l., 29:1209-1218 (1990); Lehn, Supramolecular Chemistry, VCH, Weinheim
and
New York (1995); Lehn et al., Comprehensive Supramolecular Chemistry,
Pergamon,
New York, 11 vols., ( I 996); Connet al., Chem. Rev., 97:1647-1668 ( 1997);
Chapman et
al., Tetrahedron, 53:15911-15945 (1997); Fyfe et al., Acc. Chem. Res., 30:393-
401
(1997); Ciferri, PrOQ. Polym Sci., 20:1081-1120 (1995); Lehn et al., Chem.
Macromol.
S_ymp., 69:1-17 (1993)). One-, two-, and three-dimensional supramolecular
structures
have been designed and constructed by using weak non-covalent interactions
such as
hydrogen bonding (Zimmerman et al., Science, 271:1095-1098 (1996)), metal-
ligand
complexes (Goodgame et al., Anew. Chem.. Int. Ed. En~l., 34:574-575 (1995);
Beissel
et al., Anew. Chem.. Int. Ed. Engl., 35:1084-1086 (1996)), and n-n stacking
interactions
(Ashton et al., J. Am. Chem. Soc., 1 I 8:4931-495 I ( 1996)). However. up to
now, discrete
synthetic supramolecular structures with desired functionality remain a rarity
and
represent a great challenge (Lehn, Angew. Chem.. Int. Ed. Engl., 27:89-112
{1988); Lehn,
Supramolecular Chemistry Concepts and Perspectives, VCH, Weinheim, Germany
( 1995); Whitesides et al., Science, 254:13 I2-1319 ( 1991 ); Terfort et al.,
Nature, 386 et
seq. ( 1997); Bowden et al., Science, 276:233 et seg. ( 1997); Whitesides et
al., Acc. Chem.
Res., 28:37 et seg. (1995); Lindsey, New J. Chem., 15:153-180 (1991); Gomez-
Lopez et
al., Nanotechnolo~y, 7:183-192 ( 1996); Lawrence et al., Chem. Rev., 95:2229-
2260
( 1995); Conn et al., Chem. Rev., 97:1647 et seq. ( 1997); Zimmerman et al.,
Science,
271:1095-1098 (1996); (Goodgame et al., Aneew. Chem.. Int. Ed. E~, 34:574-575
(1995); Beissel et al., Aneew. Chem.. Int. Ed. En~l., 35:1084-1086 (1996); and
Ashton et
al., J. Am. Chem. Soc., 118:4931-4951 ( 1996)). One of the most important
reasons is
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that the number of building subunits for construction of such multicomponent
systems is
quite small, leading to limited sizes of the resulting supramolecular
structures and their
poor functionality. In order to achieve 3-D well-defined nanostructures and
microstructures with desired functionality, more extended controls of chemical
interactions in two or more dimensions are needed. Much larger objects are
needed for
many near term technological applications, including drug delivery systems,
microreactors, biomimetic structures, biosensors, and imaging materials. In
principle, the
best prospects for achieving robust, functional, and technologically important
self
assembled mesostructures larger than 50 nm would seem to be through
supramolecular
polymer chemistry. This is because the characteristic length scales of polymer
chains are
already on the order of 5-100 nm. In fact, nanostructured assemblies of
segregated block
copolymers (e.g., micelles, layered thin films, microphase separated
materials, adsorbed
layers. and liquid crystals) and phase separated polymer blends with length
scales on the
order of 5-100 nm are already well known (Halperin et al., Adv. Polvm. Sci.,
100:31-71
(1992); Tuzar et al., Surface and Colloid Science, 15:1-83 (1993); Weber et
aI., Ed.
Solvents and Self Organization of Polymers, Kluwer Academic, Dordrecht (
1996); Zhang
et al., Science, 272:1777-1779 ( 1996); Chen et al., Science, 273 :343-346 (
1996)).
However, the nanostructured assemblies of current block copolymers lack
functionality
and control of size, interfaces, order, and 3-D shape due to the inability to
control the
underlying non-covalent intermolecular interactions between the macromolecular
building blocks (Whitesides et al., Science, 254:1312-1319 (1991)). Further,
self
assembly or aggregation experiments, such as micellization and adsorption in
selective
solvents, on flexible coil-coil block copolymers have been widely reported in
the past 30
years (Halperin et al., Adv. Polym. Sci., 100:31-71 (1992); Tuzar et al.,
Surface and
Colloid Science, 15:1-83 (1993); Weber et al., Ed. Solvents and Self
Organization of
Polymers, Kluwer Academic, Dordrecht (1996); Zhang et al., Science, 272:1777-
1779
( 1996); Chen et al., Science, 273:343-346 ( 1996); MacDonald et al., Chem.
Rev.,
94:2383-2420 (1994)); however, few such reports can be found for rod-coil
block
copolymers. Two main aspects of supramolecular polymer chemistry have been
reported: (i) the successful synthesis of diverse main-chain and side-chain
polymers by
molecular recognition driven self assembly of complementary monomers or
oiigomers
(Lehn et al., Chem. Macromol. Sump., 69:1-17 (1993), Stewart et al.,
Macromolecules,
30:877-884 (1997); Kato et al., Macromolecules, 29:8734-8739 (1996)); and (ii)
the
synthesis of flexible-chain polymers with tapered, rigid, side groups which
self organize
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into tubular architectures akin to the tobacco mosaic virus (TMV) (Percec et
al., Nature,
391:161-164, (1998)). However, the use of synthetic polymers as subunits for
molecular
recognition driven self assembly of large discrete aggregates and
mesostructures remains
largely unexplored.
Block copolymers can produce numerous phase-separated microstructures
and nanostructures that are of wide scientific and technological interest
(Muthukumar et
al., Science, 277:1225-1232 (1997); Chen et al., Science, 277:1248-1253
(1997); Park et
al., Science, 276:1401-1404 ( 1997); Bates, Science. 251:898-905 ( 1991 );
Milner, Science,
251:905-914 ( 1991 ); Fredrickson et al., Annu. Rev. Mater. Sci., 26:501-S50 (
1996);
Halperin et al., Adv. Polym. Sci., 100:31-71 (1992); Tirrell, Acc. Chem. Res.,
30:281-308
1 S ( 1997); Noshay et al., Block Copolymers: Overview and Critical Survey,
Academic
Press, New York ( 1977); Chen et al., Science, 273:343-346 ( 1996); Chen et
al.,
Macromolecules, 28:1688-1697 (1995); Radzilowski et al., Macromolecules.
26:879-882
(1993); Radzilowski et al., Macromolecules, 27:7747-7753 (1994); Widawski et
al.,
Nature, 369:387-389 (1994); Vernino et al., Polvm. Mater. Sci. En~., 71:496-
497 (1994);
Tuzar et al., Surface and Colloid Science, 15:1-83 (1993); Weber et al.,
Solvents and
Self Organization of Polymers, Kluwer Academic, Dordrecht ( 1996); Gast, Acc.
Chem.
Res., 30:259-280 ( 1997); Vagberg et al., Macromolecules, 24:1670-1677 ( 1991
);
Nagarajan et al., Lan~muir, 2:210-215 (1986); Nagarajan, Acc. Chem. Res.,
30:121-165
( 1997); Chen et al., Macromolecules, 29:6189-6192 ( 1996); Chen et al., Appl.
Phys. Lett.,
70:487-489 ( 1997); Semenov et al., Sov. Phys. JETP, 63:70-79 ( 1986);
Semenov, Mol.
Crvst. Lig. Cr_vst., 209:19 i -199 ( 1991 ); Halperin, Macromolecules, 23:2724-
2731 ( 1990);
Halperin, Europhys. Lett., 10:549-553 (1989); Williams et al., Macromolecules,
25:3561-
3568 (1992); Raphael et al., Makromol. Chem.. Macromol. Symp , 62:1-17 (1992);
Zhang et al., Science, 272:1777-1779 (1996); Zhang et al., Science. 268:1728-
1731
(1995); Zhang et al., J. Am. Chem. Soc., 118:3168-3181 (1996)). Conventional
applications of such block copolymer assemblies include thermoplastic
elastomers,
pressure-sensitive adhesives. colloidal dispersants, compatibilizers of
polymer blends,
foams, and surface modification (Bates, Science, 251:898-905 ( 1991 ); Milner,
Science,
251:905-914 ( 199I ); Fredrickson et al., Annu. Rev. Mater. Sci., 26:501-S50 (
1996);
Halperin et al., Adv. Polvm. Sci.,.100:31-71 (1992); Tirrell, Acc. Chem. Res.,
30:281-308
(1997); Noshay et al., Block Conolymers: Overview and Critical Survey,
Academic
Press, New York (1977); Tuzar et al., Surface and Colloid Science, 15:1-83
(1993);
Weber et al., Solvents and Self Organization of Polymers, Kluwer Academic,
Dordrecht
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{1996); Gast. Acc. Chem. Res., 30:259-280 (1997); Vagberg et al.,
Macromolecules,
24:1670-1677 ( 1991 )). Of the factors that determine the microstructure of
block
copolymers, conformational asymmetry between the blocks is perhaps the least
understood (Chen et al., Science, 273:343-346 ( 1996); Chen et al.,
Macromolecules.
28:1688-1697 (1995); Radzilowski et al., Macromolecules, 26:879-882 (1993);
Radzilowski et al., Macromolecules, 27:7747-7753 ( 1994); Widawski et al.,
Nature,
369:387-389 (1994); Vernino et al., Polvm. Mater. Sci. Eng:, 71:496-497
(1994);
Semenov et al., Sov. Phys. JETP, 63:70-79 ( 1986); Semenov, Mol. Cryst. Lig.
Crvst.,
209:191-199 (1991); Halperin, Macromolecules, 23:2724-2731 (1990); Halperin,
Europhvs. Lett., 10:549-553 (1989); Williams et al., Macromolecules, 25:3561-
3568
1 S ( 1992); Raphael et al., Makromol. Chem.. Macromol. Svmp., 62:1-17 (
1992)).
Theoretical studies of rigid-rod-flexible-coil block copolymers, in which the
ultimate
conformational asymmetry is achieved, have predicted major differences in
phase
behavior, self assembly, and microstructures compared to flexible coil-coil
block
copolymers (Semenov et al., Sov. Phys. JETP, 63:70-79 (1986); Semenov, Mol.
Cry
Liq. Cryst., 209:191-199 ( 1991 ); Halperin, Macromolecules, 23:2724-2731 (
1990);
Halperin, Europhys. Lett., 10:549-553 (1989); Williams et al., Macromolecules,
25:3561-
3568 (1992); Raphael et al., Makromol. Chem.. Macromol. SymQ, 62:1-17 (1992)).
However, only a few experimental studies of synthetic rod-coil block
copolymers have
been reported (Chen et al., Science, 273:343-346 ( 1996); Chen et al.,
Macromolecules,
28:1688-1697 (1995); Radzilowski et al., Macromolecules, 26:879-882 (1993);
Radzilowski et al., Macromolecules, 27:7747-7753 ( 1994); Widawski et al.,
Nature,
369:387-389 (1994); Vernino et al., Polvm. Mater. Sci. End, 71:496-497
(1994)). The
most detailed of these by Chen et al. involved an alpha-helical rod-like
poly(hexyl
isocyanate) as the rigid-rod block. However, such alpha-helical polymers are
known to
be capable of existing in both rod-like and flexible-coil conformations
(Halperin,
Macromolecules 23:2724-2731 ( 1990)) which can compromise their ability to
self
organize.
In addition, ordered mesoporous solids with nanoscale pore sizes are of
interest in areas such as catalysis, sensors, size- and shape-selective
separation media,
adsorbents, and scaffolds for composite materials synthesis (Kresge et al.,
Nature,
359:710-712 (1992); Sayari, Chem. Mater., 8:1840-1852 (1996); Huo et al.,
Chem.
Mater., 8:1147-1160 (1996); Zhao et al., Science. 279:548-552 (1998); Kramer
et al.,
Lan muir, 14:2027-2031 (1998); Wijnhoven et al., Science, 281:802-804 (1998)).
Those
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with pore sizes on the order of 50 nm to 30 pm are also of interest for
applications in
photonics, optoelectronics, light-weight structural materials. and thermal
insulation
(Wijnhoven et al., Science. 281:802-804 (1998); Imhor et al., Nature, 389:948
et seq.
( 1997); Yablonovitch, J. Opt. Soc. Am. B., I 0:283-295 ( 1993); Joannopoulos
et al.,
Nature, 386:143-145 (1997); Martorell et al., Phys. Rev. Lett., 65:1877-1880
(1990);
Miguez et al., Appl. Phys. Lett., 71:1148-1150 (1997); Bitzer, Honeycomb
Technology,
Chapman & Hall, London (1997)). In particular, photonic crystals or photonic
band gap
materials, i.e., structures that cam create and manipulate light signals
precisely,
transmitting certain wavelengths while blocking others, are of interest.
Photonic crystals
were first envisioned by Eli Yablonovitch more than a decade ago
(Yablonovitch, J. Opt.
Soc. Am. B., 10:283-295 ( 1993)). In these crystals, composite materials are
ordered so
that light traveling through them is modulated in a highly controlled fashion.
Groups at
Sandia National Laboratory, at Allied Signal, arid in the Netherlands have
built photonic
crystals. but most current efforts involve a great deal of technological hand-
holding:
either laborious and expensive fabrication like drilling tiny holes into a
material, or
providing a template to begin the assembly process, then somehow removing the
starting
material. Most current general methods for preparing diverse porous materials
use self
organized surfactants. block copolymers, or colloidal particles as templates
in conjunction
with sol-gel techniques (Kresge et al., Nature, 359:710-712 (1992); Sayari,
Chem. Mater..
8:1840-1852 (1996); Huo et al., Chem. Mater., 8:1147-1160 (1996); Zhao et al.,
Science,
279:548-552 ( 1998); Kramer et al., Lanemuir, 14:2027-2031 ( 1998): Wijnhoven
et al.,
Science, 281:802-804 ( I 998); Imhor et al., Nature, 389:948 et seq. ( 1997)).
In these
methods, the organic templates are eventually removed by thermal decomposition
or
solvent extraction to achieve the porous solid. Those involving inorganic
colloid
templates use solvent extractions at the final stages of making the mesoporous
solid.
Polymer latex and silica spheres are known to form colloidal crystals
(Kose et al., Colloid Interface Sci., 46:460-469 ( 1974}; Hachisu et al.,
Nature, 283:188-
189 ( 1980); Clark et al., Nature, 281:57-60 ( 1979); Pieranski et al.,
Contemp. Phys.,
24:25-73 (1983); Pusey et al., Nature, 320:340-342 (1986); Bartlett et al.,
Phys. Rev.
Lett., 68:3801-3804 (1992); van Blaaderen et al., Nature, 385:321-324 (1997);
Weissman
et al., Science, 274:959-960 (1996)), but long-range ordering of suspensions
of block
copolymer micelles into body-centered cubic (bcc) and face-centered cubic
(fcc) lattices
was observed and elucidated more recently (McConnell et al.. Phvs Rev. Lett.,
71:2102-
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2105 (1993); McConnell et al., Macromolecules, 28:6754-6764 (1995); McConnell
et al.,
Macromolecules, 30:435-444 (1997); McConnell et aL, Phys. Rev. E., 54:5447-
5455
( 1996)). Micelles of coil-coil block copolymers in a selective solvent for
one of the
blocks are spheres consisting of a dense core of the insoluble block and a
diffuse corona
of the solvated block (McConnell et al., Phys Rev. Lett., 71:2102-21 OS (
1993);
McConnell et al., Macromolecules, 28:6754-6764 (1995); McConnell et al.,
Macromolecules, 30:435-444 (1997); McConnell et al., Phvs. Rev. E., 54:5447-
5455
(1996); Webber et al., Solvents and Self Organization of Pol mers, Kluwer
Academic,
Dordrecht ( 1996); Webber, J. Phvs. Chem. B, 102:2618-2626 ( 1998); Tuzar et
al., In
Surface and Colloid Science, 15:1-83, Plenum, New York (1993); Halperin et
al., Adv.
Polvm. Sci., 100:31-71 (1992); Forster et al., Adv. Mater., 10:195-217 (1998);
Zhang et
al., J. Am. Chem. Soc., 118:3168-3181 (1996); Zhang et al., Science, 268:1728-
1731
( 1995)). Copolymer architecture and solution chemistry have been used to vary
their
diameter between about 10 to 80 nm and the corona thickness relative to the
core radius
{McConnell et al., Phys Rev. Lett., 71:2102-2105 (1993); McConnell et al.,
Macromolecules, 28:6754-6764 (1995); McConnell et al., Macromolecules, 30:435-
444
( 1997); McConnell et al., Phys. Rev. E., 54:5447-5455 ( 1996); Webber et al.,
Solvents
and Self Organization of Polymers, Kluwer Academic, Dordrecht (1996); Webber,
J.
Phvs. Chem. B, 102:2618-2626 (1998); Tuzar et al., In Surface and Colloid
Science,
15:1-83, Plenum, New York (1993); Halperin et al., Adv. Polvm. Sci., 100:31-71
(1992);
Forster et al., Adv. Mater., 10:195-217 ( 1998); Zhang et al., J. Am. Chem.
Soc.,
118:3168-3181 (1996); Zhang et al., Science, 268:1728-1731 {1995)). Micellar
crystallization into either an fcc Qr a bcc lattice is determined by the
length scale and
steepness of repulsive interactions that can be controlled by the ratio of the
coronal layer
thickness to the core radius (McConnell et al., Phys Rev. Lett., 71:2102-2105
(1993);
McConnell et al., Macromolecules, 28:6754-6764 (1995); McConnell et al.,
Macromolecules, 30:435-444 (1997); McConnell et al., Phvs. Rev. E., 54:5447-
5455
( 1996)). Theoretical studies of the possible equilibrium structures of
micelles of rod-coil
block copolymers in a selective solvent for the coil-like block have been
reported
(Semenov et al., Sov. Phvs., 63:70-79 (1986); Semenov, Mol. Cryst. Liq.
Crvst., 209:191-
199 (1991); Halperin, Macromolecules, 23:2724-2731 (1990); Holyst et al., J.
Chem.
Phvs., 96:721-729 { 1992); Muller et al., Macromolecules, 29:8900-8903 (
1996); Williams
et al., Macromolecules, 25:3561-3568 (1992); Williams et al., Phys. Rev.
Lett., 71:1557-
1560 ( 1993); Raphael et aL, Physica A, 177:294-300 ( 1991 ); Raphael et al.,
Makromol.
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Chem.. Macromol. Svmn., 62:1-I 7 ( 1992)). Because of the perceived difficulty
of
efficient space-filling packing of rod-like blocks into a spherical or a
cylindrical core,
various alternative space-filling core-corona models. such as disk-like
cylindrical micelles
and monolayer and bilayer ''hockey puck" micelles, have been proposed (Semenov
et al.,
Sov. Phys., 63:70-79 ( 1986); Semenov, Mol. C s~q. Crvst., 209:191-199 ( 1991
);
Halperin, Macromolecules, 23:2724-2731 (1990); Holyst et al., J. Chem. Phys.,
96:721-
729 ( 1992); Miiller et al., Macromolecules, 29:8900-8903 ( 1996); Williams et
al.,
Macromolecules, 25:3561-3568 (1992); Williams et al.. Phvs. Rev. Lett.,
71:1557-1560
( 1993); Raphael et al., Phvsica A, 177:294-300 ( 1991 ); Raphael et al.,
Makromol. Chem..
Macromol. Svmn., 62:1-17 {1992)). However, experimental data have heretofore
been
unavailable to test these models (Widawski et al., Nature, 369:387-389 (1994);
Francois
et al., Adv. Mater., 7:1041-1044 (1995)). Thus, the implications of the
unusual micellar
structures of rod-coil block copolymers (Jenekhe et al., Science, 279:1903-
1907 ( 1998))
for regulating these repulsive interactions. micellar crystallization, and
crystal lattice
selection are currently unknown.
The present invention is directed toward overcoming the above-noted
deficiencies in the prior art.
SUMMARY OF THE INVENTION
The present invention relates to a method for producing microstructures,
nanostructures. or objects. This method involves providing a rod-coil block
copolymer
including a rigid-rod block and a flexible-coil block, mixing the rod-coil
block copolymer
and a selective solvent for one of the blocks which solubilizes that block,
and permitting
the rod-coil block copolymer to self assemble into organized mesostructures
with a
region of the unsolubilized block and a region of the solubiIized block.
The present invention also relates to a microstructure, nanostructure, or
object including a rod-coil block copolymer which includes a rigid-rod block
and a
flexible-coil block, wherein the rod-coil block copolymer forms an organized
mesostructure with a region of one block and a region of the other block.
Another aspect of the present invention is a method for producing a
mesoporous solid. This method involves providing a rod-coil block copolymer
including
a rigid-rod block and a flexible-coil block, mixing the rod-coil block
copolymer and a
selective solvent for the flexible-coil block which solubilizes that block,
permitting the
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rod-coil block copolymer to self assemble into organized mesostructures with a
region of
the unsolubilized block and a region of the solubilized block, evaporating the
solvent, and
permitting the organized mesostructures to self organize into a mesoporous
solid.
The present invention also relates to a method for producing a polymer
adsorption layer on a substrate. This method involves providing a rod-coil
block
copolymer including a rigid-rod block and a flexible-coil block, mixing the
rod-coil block
copolymer and a selective solvent for one of the blocks to form a solution of
rod-coil
block copolymer and solvent. inserting a substrate into the solution,
permitting the rod-
coil block copolymer to adsorb to the substrate, and removing the substrate
from the
solution under conditions effective to form an adsorption layer of a polymer
on the
substrate.
Another aspect of the present invention is a substrate with a polymeric
adsorption layer, wherein the adsorption layer is a rod-coil block copolymer
including a
rigid-rod block and a flexible-coil block, wherein one of the blocks of the
rod-coil block
copolymer is adsorbed to the substrate.
The present invention also relates to an optical article including a
substrate, a transparent conductor formed as a coating on the substrate, a
polymeric
adsorption layer including a rod-coil block copolymer including a rigid-rod
block and a
flexible-coil block, wherein one of the blocks of the rod-coil block copolymer
is adsorbed
to the transparent conductor. and a coating formed on the surface of the
adsorption layer,
wherein the adsorption layer allows the emission of polarized light.
Another aspect of the present invention is a method for encapsulating
guest molecules, macromolecules, or nanoparticles. This method involves
providing a
rod-coil block copolymer including a rigid-rod block and a flexible-coil
block, mixing the
rod-coil block copolymer with a selective solvent for one of the blocks which
solubilizes
that block to form a solution of rod-coil block copolymer and solvent, adding
guest
molecules, macromolecules, or nanoparticles to the solution, and permitting
the rod-coil
block copolymer to self assemble into organized mesostructures with a region
of the
unsolubilized block and a region of the solubilized block under conditions
effective to
encapsulate the guest molecules, macromolecules, or nanoparticles within the
mesostructure.
Yet another aspect of the present invention is an organized mesostructure
with an encapsulated guest molecule, macromolecule, or nanoparticle which
includes a
rod-coil block copolymer including a rigid-rod block and a flexible-coil
block, wherein
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the rod-coil block copolymer forms an organized mesostructure with a region of
one
block and a region of the other block and a guest molecule, macromolecule. or
nanoparticle, wherein the guest molecule. macromolecule, or nanoparticle is
encapsulated
within the mesostructure.
The present invention also relates to a method for solubilizing guest
molecules, macromolecules, or nanoparticles. This method involves providing a
rod-coil
block copolymer including a rigid-rod block and a flexible-coil block, mixing
the rod-coil
block copolymer with a selective solvent for one of the blocks which
solubilizes that
block to form a solution of rod-coil block copolymer and solvent, adding guest
molecules,
macromolecules, or nanoparticles to the solution, and permitting the rod-coil
block
copolymer to self assemble into organized mesostructures with a region of the
unsolubilized block and a region of the solubilized block under conditions
effective to
solubilize the guest molecules, macromolecules. or nanoparticles.
The rod-coil block copolymers of the present invention form robust,
functional, structurally well-defined, three-dimensional nanostructures,
microstructures,
and objects. The nanostructures, microstructures, and objects may be used for
encapsulating guest molecules, macromolecules, or nanoparticles. In addition,
the
nanostructures, microstructures, and objects may be used to form mesoporous
solids,
without a template, for use in various optical applications, tissue
engineering and
biomaterials, molecular electronic devices, optically tunable and responsive
coatings, and
the processing of "soft" colloidal materials. Further, the rod-coil block
copolymers of the
present invention may be used to form an adsorption layer of a polymer.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 shows preferred rod-coil block copolymer architectures of the
present invention.
Figure 2 shows preferred rigid-rod blocks for the rod-coil block
copolymers of the present invention.
Figure 3 shows additional preferred rigid-rod blocks for the rod-coil block
copolymers of the present invention.
Figure 4 shows preferred flexible-coil blocks for the rod-coil block
copolymers of the present invention.
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Figure ~ shows the synthetic scheme for the diblock copolymers PPQso-b-
PS2ooo~ PPQso-b-PSiooo, PPQso-b-PS3oo~ PPQio-b-PSi3o~ PPQ~o-b-PS~ooo, PPQio-b-
PS3oo~
and PPQ,o-b-PSi3o (54a-g).
Figure 6 shows the synthetic scheme for the triblock copolymers PPQso-b-
PSsoo-b-PPQso~ PPQso-b-PSZSO-b-PPQso~ and PPQso-b-PS~2o-b-PPQso (SSa-c).
Figure 7 shows the chemical structure and schematic illustration of the
self assembly of poly (phenylquinoline)-block-polystyrene ("PPQ-b-PS") rod-
coil block
copolymers into hollow aggregates.
Figure 8 shows some relevant hydrogen-bonded structural motifs for
influencing molecular packing and 3-D structure.
I S Figure 9 shows hydrogen-bonded layers and bilayers of AB rod-coil block
copolymers which are structural motifs for self assembly of 3-D structures.
Figure 10 shows hydrogen-bonded tapes for self assembly of 3-D
structures by ABA and BAB rod-coil block copolymers.
Figure 11 shows examples of rod-coil block copolymers.
Figure 12 shows the molecular structure of the rod-coil block copolymer
PPQmPS" and schematic illustration of its hierarchical self assembly into
ordered
mesoporous materials.
Figure 13 shows examples of self assembly of rod-coil block copolymers
at surfaces of substrates to form adsorption layers.
Figure 14 shows schematic illustrations of the self assembly of rod-coil
PPQ-b-PS diblock and PPQ-b-PS-b-PPQ copolymers into hollow aggregates.
Figures 15A-D show the optical (Figures I SA to C) and scanning electron
(Figure 1 SD) micrographs of the typical morphologies of PPQ;o-b-PS3~. Drops
of dilute
solutions (0.5 to 1.0 mg/ml) of the rod-coil block copolymers were spread and
dried on
glass slides and aluminum substrates, respectively. (Figure I SA) spherical
aggregates ( 1:
I TFA:DCM, v/v, 95 °C); (Figure I SB) lamellae ( 1:1 TFA:DCM, 25
°C); (Figure I SC)
cylinders (9:1 TFA:DCM, 25 °C); (Figure 15D) vesicles (1:1 - 1:4
TFA:DCM, 25 °C).
Figures 16A-F show optical (Figure 16A and Figure 16C) and
fluorescence (Figure I6B, Figure I 6D-F) micrographs of the typical
morphologies of
PPQso-b-PS3~ (54c). Drops of dilute solutions (0.5 to 1.0 mglml) of the
diblock
copolymers were spread and dried on glass slides. Spherical aggregates (Figure
16A)
under cross-polarizers, {Figure 16B) fluorescence lamp (7:1 TFA:DCM, v/v,
25°C);
lamellae (Figure 16C) under cross-polarizers, (Figure 16D) under fluorescence
lamp (I:1
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TFA:DCM, 25°C); (Figure 16E) cylinders (9:1 TFA:DCM, 25°C);
(Figure 16F) rings ( 1:4
TFA:DCM, 25°C).
Figures 17A-F show optical (Figure 17A and Figure 17C-F) and
fluorescence (Figure 17B) micrographs of the typical morphologies of diblock
copolymer
54b, 54e, 54f, and 54g. (Figure 17A) spherical aggregates from PPQ;o-b-PS,ooo
(54b) (7: I
TFA:DCM, v/v, 25°C); (Figure 17B) cylinders from PPQ;o-b-PS,ooo
(54b) (9:1
TFA:DCM, 25°C); (Figure 17C) lamellea from PPQ,o-b-PS,ooo (54e) (1:1
TFA:DCM,
25°C); (Figure 17D) lamellea from PPQ,o-b-PS3oo (54f) (I:I TFA:DCM,
25°C); {Figure
17E) lamellae from PPQIO-b-PS,3o (54fj (1:1 TFA:DCM, 25°C); (Figure
17F) lamellae
from PPQ~o-b-PSi3o (54f) (1:1 TFA:DCM, 25°C).
I 5 Figure I 8 shows schematic illustrations of the self assembly of rod-coil
PPQ-b-PS diblock copolymers.
Figures I 9A-B show photoluminescence (''PL") emission and excitation
("PLE") (Figure 19A)spectra and PL decay dynamics of spherical, lamellar, and
cylindrical aggregates of PPQ;o-b-PS3oo (Figure 19B). PL emission spectra are
for 380-
nm excitation. and PLE spectra were obtained by monitoring the emission peaks.
PL
decay data are for 380-nm laser excitation in time-correlated single-photon
counting
experiments.
Figures 20A-F show optical and fluorescence micrographs of hollow
spherical vesicles from triblock copolymers PPQ;o-b-PS;oo-b-PPQ;o (55a)
(Figure 20A,
Figure 20B); PPQ;o-b-PSZSO-b-PPQso(55b) (Figure 20C, Figure 20D); PPQ;o-b-
PS~ZO-b-
PPQ;o (55c) (Figures 20E, Figure 20F). Figures 20A. 20C and 20E were taken
under
cross-polarizers. The samples were prepared by allowing drops of dilute
solutions (0.5 to
1.0 mg/ml) of the triblock copolymers to spread and be dried on hot glass
slides (6:4
TFA:DCM, v/v, 95 °C).
Figures 21 A-F show optical and fluorescence micrographs of vesicles
from diblock and triblock copolymers PPQ;o-b-PS;oo-b-PPQ;o (55a) (Figures 21A-
D) and
PPQ;o-b-PS2;o-b-PPQ;o (55b) (Figures 21 E-F). The images were taken in-situ
from
sample solutions (6:4 TFA:DCM, 25°C, 1.0 mg/ml) sealed inside 6 mm x 50
mm tubes.
Figures 21 A, 21 E, and 21 F were take under bright field. Figure 21 C was
taken under
cross-polarizers. Figures 21 B and 21 D were taken when excited with 400-nm
light.
Figures 22A shows schematic illustrations of the H-aggregates (Figure
22A) and J-aggregates (Figure 22B) formed by rod-coil block copolymers.
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Figures 23A-B show Photoluminescence (PL) emission and excitation
(PLE) spectra {Figure 23A) and PL decay dynamics of spherical aggregates from
triblock
copolymers 55a-c and spherical, lamellar, and cylindrical aggregates from
diblock
copolymers 54a-g (Figure 23B). PL emission spectra are for 380-nm excitation,
and PLE
spectra were obtained by monitoring the emission peaks. PL decay data are for
380-nm
laser excitation in time-correlated single-photon counting experiments.
Figures 24A-F show scanning electron micrographs of the spherical
aggregates self assembled from PPQ;o-b-PS3oo (Figure 24A, Figure 24B, Figure
24E,
Figure 24F) and PPQ,o-b-PS3oo (Figure 24C, Figure 24D). All these aggregates
were
prepared by spreading dilute solution (0.1 wt%) with a solvent ratio TFA:DCM
of 7/1
onto aluminum substrates (25°C).
Figures 25A-D show fluorescence photomicrographs of PPQ;o-b-PS3oo
aggregates as described in Figure 10: (Figure 25A) Spherical, (Figure 25B)
lamellar,
(Figure 25C) cylindrical, and (Figure 25D) vesicular aggregates.
Figures 26A-C show a fluorescence photomicrograph of PPQ-b-PS
showing spheres (Figure 26A), lamellae (Figure 26B), and cylinders (Figure
26C).
Figure 27 shows examples of 3-D shaped objects that could be prepared by
molecular self assembly.
Figures 28A-F show scanning electron micrographs of the typical
morphologies of triblock copolymers PPQ;o-b-PS;oo-b-PPQ;o (55a) (Figure 28A,
Figure
28B, Figure 28E); PPQ;o-b-PS2so-b-PPQ;o (55b) (Figure 28C, Figure 28F); PPQ;o-
b-
PS,2o-b-PPQ;o (55c) (Figure 28D). Drops of dilute solutions (0.5 to 1.0 mg/ml)
of the
triblock copolymers (6:4 TFA:DCM, 25°C) were spread and dried on
aluminum
substrates (Figures 28A-E) or a copper grid (Figure 28F), respectively.
Figures 29A-D show TEM images of aggregates prepared from 5:5
TFA:DCM solutions at 20 °C. (Figure 29A) PPQ,o-b-PS3oo (54th; (Figure
29B) PPQ;o-b-
PS3oo (54c); (Figure 29C) PPQ;o-b-PS;oo-b-PPQ;o (55a); (Figure 29D) PPQ;o-b-
PS2so-b-
PPQ;o (55b).
Figures 30A-C show optical micrographs of aggregates of PPQ;o-b-PS3oo
containing 5 wt.% solubilized Cbo. Figure 30A shows a sample from 1:1 TFA:DCM
under bright field. Figure 30B shows a sample from 1:1 TFAaoluene under cross-
polarizers. Figure 30C shows a schematic illustration of the cross-section of
a spherical
block copolymer aggregate with encapsulated fullerene-C6o.
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Figure 31 shows TGA thermograms of homopolymer PPQ and PS, diblock
copolymers 54a-g, and triblock copolymers 55a-c obtained in flowing nitrogen
with a
heating rate of 10 °c/min.
Figure 32 shows ~H NMR shifts in b (ppm) of PPQ;o-b-PS;oo-b-PPQso
(55a) in deuterated nitrobenzene/GaCl3.
Figure 33 shows the FTIR spectrum of PPQ,o-b-PS3oo (54~ in NaCI disk.
Figure 34 shows the micellar solubilization of Cbo and Coo in TFA/DCM or
TFA/toluene when PPQ;o-b-PS3oo (54c) or PPQ,o-b-PS3oo (54f~ was present.
Figures 35A-C show optical absorption spectra of solutions of (Figure
35A) pure PPQso-b-PS3oo (1:1 TFA:DCM, 0.05 wt.%), (Figure 35B) 5 wt % Cbo/
PPQso-
b-PS3oo ( 1:1 TFA:DCM, 0.05 wt.%), and (Figure 35C) Cbo in CSa (0.05 wt.%).
Inset is the
magnified spectrum of the 5 wt.% Cbo/ PPQ;o-b-PS3oo in the region of 450-700
nm.
Figure 35 shows the optical absorption spectra of solutions of ~ wt.% Coo/
PPQ;o-b-PS3oo and 5 wt.% C7o/PPQ,o-b-PS3oo (1:1 TFA:DCM, 0.0~ wt.%). Also
shown
for comparison are the spectra of Coo in CS2 (0.05 wt.%) and pure PPQ;o-b-
PS3oo ( 1:1
TFA:DCM, 0.05 wt.%).
Figure 37 show the normalized absorbance of fullerene-PPQ-PS solutions
as a function of fullerene loading: (Figure 37A) Cbo-PPQ-PS system and (Figure
37B)
Coo-PPQ-PS system. The solvent is TFA/DCM (1/1, v/v).
Figure 38 shows fluorescence (Figures 38A and B) and polarized optical
(Figure 38C) micrographs of aggregates of PPQ;o-b-PS3oo containing 0.1 wt.%
solubilized
Coo and (Figure 38D) fluorescence optical micrograph of 0.1 wt.% C6o in PPQ;o-
b-PS3oo.
Figure 39 shows Fluorescence (Figures 39A and B) and polarized optical
(Figure 39C) micrographs of aggregates of PPQso-b-PS3oo containing 1 wt.%
solubilized
Cbo prepared from 4:1 TFAaoluene.
Figure 40 shows fluorescence (Figures 40A and C) bright field (Figure
40B) and polarized optical (Figure 40D) micrographs of aggregates of PPQso-b-
PS3oo
containing 6 wt.% solubilized Cbo prepared from 1:1 TFA:DCM.
Figure 41 shows bright field optical micrographs of films of PPQ;o-b-PS3oo
aggregates dried from solutions containing 8 wt.% (Figure 41 A) and 10 wt.%
(Figure
41B) C6o.
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Figure 42 shows the average diameters of spherical fullerene/PPQ-PS
aggregates as a function of fullerene loading and block copolymer composition.
The line
is only a guide to eyes.
Figure 43A shows DSC scans of PS homopolymer (1), pure C6o (2), and 3
wt.% C6o/PPQ;o-b-PS3oo aggregates. Figure 43B shows DSC scans of 1 wt.% C6o
dispersed in PS homopolymer. The inset is the scan magnified in the region
250K to
290K.
Figures 44A-C show PL and PLE spectra of spherical PPQ;o-b-PS3oo
aggregates containing no C6o (a), 1 wt.% C6o (Figure 44B) and 5 wt.% C6o
(Figure 44C).
The excitation wavelength for the PL spectra were 380 nm (Figure 44A), 360 nm
(curve
I S 1 ) and 475 nm (curve 2) (Figure 44B), and 475 nm (Figure 44C). The
emission
wavelengths monitored for the PLE spectra were 480 nm (Figure 44A), 480 nm
(curve 3)
and 600 (curve 4) (Figure 44B), and 600 nm (Figure 44C).
Figure 45 shows a fullerene solubilization and encapsulation induced
transformation of PPQ-PS rod-coil diblock copolymer chains in H-aggregates to
J-
aggregates.
Figures 46A-B shows TGA thermograms of block copolymer samples
PPQ;o-b-PS3oo (54c) and PPQ,o-b-PS3oo (54f7 and the PPQ and PS homopolymers at
10
°C/minute in Nz.
Figures 47A-C show fluorescence photomicrographs of solution cast
micellar films of PPQio-b-PS3oo obtained by ambient air drying of different
rod-coil block
solution concentrations in CSC: (Figure 47A) 0.005 wt.%; (Figure 47B) 0.01
wt.%; and
(Figure 47C) 0.05 wt.%. Arrows in B indicate regions of self ordering.
Figures 48A-D show (Figure 48A) Polarized optical and (Figures 48B and
C) SEM micrographs of microporous micellar films obtained from a 0.5 wt.%
PPQ;o-b-
PS2ooo rod-coil block copolymer~solution by solution casting on a glass slide
and an
aluminum substrate, respectively. The SEM samples were coated with a 10 nm
gold
layer. The SEM image in 48B is the top view and that in 48C is of the same
sample tilted
45° from the beam axis to reveal 3-D structure. Figure 48D shows a
variation of hole
diameter (D), periodicity (p) and minimum wall thickness (h) of ordered
microporous
films with the number of PS repeat units in the rod-coil block copolymers.
Figures 49A-B show (Figure 49A) a polarized optical micrograph of a
microporous micellar film of PPQ,o-b-PS3oo obtained from a 0.5 wt % solution
containing
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~ mg Coo /g rod-coil block copolymer and (Figure 49B} the dependence of
microstructural
parameters of micellar films of the same rod-coil block copolymer on fullerene
loading.
Figures BOA-B show the (Figure SOA) PL emission (390-nm excitation)
and PLE excitation (460-nm emission) spectra of a micellar film of PPQ~o-b-
PS3oo and of
the same rod-coil block copolymer chains homogeneously dispersed (0.1 wt.%) in
a
polyethylene oxide) (PEO) film and (Figure SOB) PL decay dynamics of the same
samples in A when excited at 360 nm and monitored at 490 nm.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a method for producing microstructures,
nanostructures, or objects. This method involves providing a rod-coil block
copolymer
including a rigid-rod block and a flexible-coil block, mixing the rod-coil
block copolymer
and a selective solvent for one of the blocks which solubilizes that block,
and permitting
the rod-coil block copolymer to self assemble into organized mesostructures
with a
region of the unsolubilized block and a region of the solubilized block.
Preferred rod-coil block copolymer architectures for the present invention
include AB rod-coil diblock and ABA rod-coil-rod triblock copolymers
illustrated in
Figure l, where A denotes a rigid-rod block and B denotes a flexible-coil
block.
Preferred rigid-rod blocks include polyquinolines (1) (Jenekhe et al.,
Science 279:1903-1907 (1998); Agrawal et al., Macromolecules 26:895-905
(1993),
which are hereby incorporated by reference), polyquinoxalines (2), polyp-
phenylenes)
(3, 4), polyp-phenylene vinylenes) (5, 6), polypridines (7), poly(pyridine
vinylenes) (8),
poly(naphthylene vinylenes) (9, 10), polythiophenes (11), poly(thiophene
vinylenes) (12),
polypyrroles (13), polyanilines (14), polybenzimidazoles (15),
polybenzothiazoles (16),
polybenzoxazoles (17), and polybenzobisazoles (18-20) (Figure 2). Additional
preferred
rigid-rod blocks include aromatic polyamides (2I-24), aromatic polyhydrazides
(25-27),
aromatic polyazomethines (28-30), aromatic polyesters (31-33), and aromatic
polyimides
(34) (Yang, Aromatic Hi h Strength Fibers, Wiley-Interscience, New York, (
1989),
which is hereby incorporated by reference) (Figure 3).
Preferred flexible-coil blocks include polystyrene (35, PS), poly(a-methyl
styrene) (36, PMS), polyethylene oxide (37, PEO), polypropylene oxide) (38,
PPO),
poly(acrylic acid) (39, PAA), poly(methylacrylic acid) (40, PMAA), poly(2-
vinylpyridine) (41, P2VP), poly(4-vinylpyridine) (42, P4VP), polyurethane (43,
PU),
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polyvinyl pyrrolidone) (44), poly(methyl methacrylate) (45, PMMA), poly(n-
butyl
methacrylate) (46, PBMA), polyisoprene (47, PI), poly(butadiene) (48, PB),
poly(dimethylsiloxane) (49, PDMS), polystyrene sulfonic acid) (50, PSSA), and
sodium
polystyrene sulfonate) (51, PSSNa) (Webber et al., Solvents and Self
Organization of
Polymers. Kluwer Academic, Dordrecht, (1996); Hamley, The Physics of Block
Copolymers, Oxford University Press, Oxford, ( 1998), which is hereby
incorporated by
reference) (Figure 4}.
Preferred selective solvents include those solvents or mixtures of solvents
which are selective for only the parent rigid-rod polymer, only the parent
flexible-coil
polymer, and solvents or mixtures of solvents which dissolve only one block in
a block
1 S copolymer. As known in the art, a selective solvent is chosen by selecting
a solvent from
the list of solvents known in the art and commonly tabulated for the parent
rigid-rod
polymer and for the parent flexible-coil polymer (Brandrup et al., Polymer
Handbook, 3~a
ed., Wiley-Interscience, New York, (1989), which is hereby incorporated by
reference) or
mixtures of such known solvents for respectively the rigid-rod and flexible-
coil polymers.
Thus, for the rod-coil poly(phenylquinoline) (PPQ)-block-polystyrene (PS) (PPQ-
PS)
diblock copolymers, PPQ-PS-PPQ triblock copolymers, polyquinoxaline (PQx)-
block-
polystyrene (PQx-PS) diblock copolymers. or PQx-PS-PQx triblock copolymers,
preferred selective solvents for the rigid-rod block include trifluoroacetic
acid ("TFA"),
mixtures of TFA and dichloromethane, and mixtures of TFA and toluene.
Preferred
selective solvents for rod-coil block copolymers comprising PS or PMS blocks
include
carbon disulfde (CSZ), 1-nitropropane, ethylbenzene, cyclohexanone, and
mixtures
thereof. Preferred selective solvents for rod-coil block copolymers comprising
PEO,
PAA, PMAA, PSSA, or PSSNa blocks include water, dioxane/water, formamide, N,N-
dimethyl-formamide ("DMF"), ethanol, methanol, and mixtures thereof.
Preferred temperatures of the solution or surface where self organization
of the rod-coil block copolymer is to take place varies from 20 °C up
to about 5-25 °C
above the boiling point of the solvent. Typically, the self assembly
temperature is
between room temperature (about 22-25 °C) and 100 °C.
Preferred concentrations of rod-coil block copolymer in solution at room
temperature for self assembly of nanostructures, microstructures, or objects
include
concentrations greater than the critical micelle concentration (cmc) or the
critical
vesiculation concentration (cvc). The cmc (or cvc) of a block copolymer is the
concentration below which the copolymer exists as individual molecules or
chains in
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solution and above which it exists primarily as aggregated species, and
typically has
values of about 10-8 to 10~ Molar or less (Tuzar et al., Surface and Colloid
Science, 15:1-
83 (1993); Weber et al.. Solvents and Self Or~~anization of Polymers. Kluwer
Academic,
Dordrecht ( 1996), which are hereby incorporated by reference). A preferred
solution
concentration for self assembly of the rod-coil block copolymers of the
invention is
between 10~ wt.% (0.0001 wt.%) to 10.0 wt.% at room temperature. Evaporation
of
solvent from solutions initially at room temperature by ambient air drying or
by the
application of heat necessarily changes the initial solution concentration.
In a preferred embodiment of the present invention, the rod-coil block
copolymer has the diblock architecture: rod blockmcoil block". Preferably, m=1
to 500
and n=10 to 5,000.
In another preferred embodiment, the rod-coil block copolymer has the
triblock architecture: rod blockmcoil block"rod blockm. Preferably, m=1 to X00
and n=10
to 5,000.
Preferred rod-coil block copolymers for use in the present invention are
poly(phenylquinoline)-block-polystyrene ("PPQ-b-PS") (54a-g, Figure 5) and
poly(phenylquinoline)-block-polystyrene-block-poly(phenylquinoline) ("PPQ-b-PS-
b-
PPQ") (SSa-c, Figure 6). The poly (phenylquinoline) (1, PPQ) homopolymer is a
conjugated polymer with high modulus and thermal stability, and found to
exhibit liquid
crystalline ordered phases in solution (Sybert et al., Macromolecules, 14:493-
502 ( 1981 ),
which is hereby incorporated by reference). It is soluble in strong acid. such
as sulfuric
acid, trifluoroacetic acid. and its optical, optoelectronic, and
electrochemical properties
have been reported (Agrawal et al., Macromolecules 26:895-905 (1993); Agrawal
et al.,
Chem. Mater., 8:579-589 (1996), which are hereby incorporated by reference).
The
polystyrene (35, PS) is a well-known non-photoactive and non-electroactive
polymer,
soluble in common organic solvents such as tetrahydrofuran (THF),
dichloromethane,
carbon disulfide (CS2), and chloroform. Thus, PPQ-b-PS (54) and PPQ-b-PS-b-PPQ
(55)
represent amphiphilic rod-coil diblock (Figure 5) and rod-coil-rod triblock
copolymers
(Figure 6). Amphiphilic PPQ-b-PS (Figure 7) rod-coil block copolymers self
organize
into robust, micrometer-scale, spherical, vesicular, cylindrical, and lamellar
aggregates
from solution. The heterocyclic rigid-rod polyquinoline block of the rod-coil
block
copolymers allows tuning of their amphiphilicity. For example, through
protonation or
quarternization of the imine nitrogen (Sybert et al., Macromolecules, 14:493-
502 ( 1981 );
Agrawal et al., Macromolecules, 26:895-905 (1993); Agrawal et al., Chem.
Mater.,
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8:579-589 ( 1996), which are hereby incorporated by reference), the rod-like
block can be
turned into a polyelectrolyte. The n-conjugated nature of the rigid-rod block
confers
electroactive and photoactive properties (Sybert et al., Macromolecules,
14:493-502
( 1981 ); Agrawal et al., Macromolecules, 26:895-905 ( 1993); Agrawal et al.,
Chem.
Mater.. 8:579-589 ( 1996); Jenekhe et al., Photonic and Optoelectronic
Polymers,
American Chemical Society, Washington, DC, ( 1997), which are hereby
incorporated by
reference) on the block copolymers while providing novel ways of probing the
self
assembly, molecular packing, morphology, and dynamics of the polymeric
amphiphiles
by optical and photoelectronic techniques. The PPQ-b-PS copolymers, in
selective
solvents for PPQ, form large aggregates with various morphologies (spheres,
vesicles,
cylinders, and lamellae) that can be observed by optical microscopy (OM).
The amide linkage at the rod-coil interface in each block copolymer chain
provides a means of strong intermolecular interactions, through hydrogen
bonding, that
enhance the stability of self organized structures. More specifically,
secondary amide
linkages (-NH-CO-) and their associated hydrogen bonding, when strategically
placed,
can limit the number of possible arrangement of molecules in space with
respect to one
another as has been successfully done in the field of crystal engineering of
hydrogen-
bonded solid state structures (Figure 8) (MacDonald et al., Chem. Rev.,
94:2383-2420
( 1994), which is hereby incorporated by reference). Amide linkages may be
incorporated
at the interfaces in AB and ABA block copolymers as shown in Figures 1, 9, and
10. In
addition to the strong and directional intermolecular interactions, such
hydrogen bonding
also introduces the highly desired and novel feature of well-defined, sharp
and precisely
controllable interfaces (Figures 9 and 10). In addition, a large
conformational asymmetry
is introduced between the blocks by the presence of rigid-rod A blocks and
flexible-coil B
blocks in the same macromolecule. The conformational asymmetry introduces
amphiphilicity and enhances the driving force for microphase separation and
hence self
assembly of rod-coil block copolymers; this further restricts the possible
orientation of the
macromolecules in space (Figures 9 and 10). Moreover, although van der Waals
interactions are in general nondirectional and very weak in flexible chain
polymers, and
heretofore difficult to use for molecular self assembly (Whitesides et al.,
Science,
254:1312-1319 ( 1991 ), which is hereby incorporated by reference), they are
relatively
more directional and can be very strong between rigid-rod polymers. Thus rigid
rod-like
blocks also provide well-defined surfaces for directing and maximizing van der
Waals
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forces. Synthesis of rod-coil block copolymers imprinted with these structural
features
produce macromolecular building blocks with encoded information for 3-D self
assembly. Many specific structures are possible fox implementing these ideas.
Those
shown in Figures 1-11 are examples that can be readily synthesized and
characterized.
These structures include blocks that are either soluble in organic solvents or
in aqueous
media. The conjugated structure of some of the rod-like blocks is designed to
introduce
electroactive and photoactive properties into self assembled mesostructures.
However,
non-conjugated rigid-rod blocks can also be readily utilized as shown in
Figure 3.
Some specific areas of possible near-term technological impact due to the
rod-coil block copolymers of the present invention are novel types of
ultralarge micelles.
colloids, microemulsions and macroemulsions that are thermodynamically stable,
polymer surface modification, photoregulation of surface properties, novel
molecular
containers for encapsulation of large molecules or nanoparticles, novel self
assembled
nanoporous/microporous materials for photonic band gap applications,
separation
membranes. scaffolds for tissue engineering, and photonic and optoelectronic
materials.
In another embodiment, the present invention further includes evaporating
the solvent after permitting the rod-coil block copolymer to self assemble
into organized
mesostructures with a region of the unsolubilized block and a region of the
solublized
block.
In another aspect of the present invention, the rod-coil block copolymers
of the present invention may be also be used as a compatibilizer in a method
of making
molecular composites and nanocomposites of flexible-coil polymers and rigid-
rod
polymers. This method involves providing a solution of flexible-coil polymer
and rigid-
rod polymer and adding a rod-coil block copolymer of the present invention to
the
solution under conditions effective to form a substantially fine dispersion of
the flexible-
coil polymer and rigid-rod polymer.
Because of the fundamental thermodynamic incompatibility of mixtures of
rod-like and coil-like polymers (Flory, Macromolecules, 11:1138-1141 (1978);
Roberts,
et al., Chem. Mater., 6:135-145 (1994), which are hereby incorporated by
reference), they
phase separate into large domains. Among the consequences of this macrophase
separation are poor mechanical properties, poor optical properties such as
transparency,
and lack of control and stability in the morphology of the blend. As a novel
class of
polymeric surfactants, the rod-coil block copolymers of the present invention
function as
compatibilizers of mixtures of rod-like and coil-like polymers by segregating
to the
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~ interface between the phases in ways similar to how coil-coil block
copolymers are
known to compatibilize blends of coil-like polymers (Datta. et al., Polymeric
Compatibilizers, Hamser Publishers, Munich, ( 1996), which is hereby
incorporated by
reference). The compatibilization mechanism is thus accomplished by reducing
the
interfacial tension between the rigid-rod polymer and flexible-coil polymer
phases and by
reducing the tendency of phases/domains to coalesce, both factors leading to
reduction in
phase sizes and improved adhesion between the phases. By use of the rod-coil
block
copolymers of the present invention in this way to compatibilize mixtures of
rigid-rod and
flexible-coil polymers, blends, nanocomposites, and molecular composites with
fine
dispersion (smaller phase sizes) are obtained, leading to improved mechanical
properties
for structural applications and improved optical and transport (barrier)
properties. The
present rod-coil block copolymers axe thus useful means to control and
stabilize the
morphology and properties of blends, nanocomposites, and molecular composites
of rod-
like and coil-like polymers.
The present invention also relates to a microstructure, nanostructure, or
object including a rod-coil block copolymer which includes a rigid-rod block
and a
flexible-coil block, wherein the rod-coil block copolymer forms an organized
mesostructure with a region of one block and a region of the other block.
Another aspect of the present invention is an optical article including a
microstructure, nanostructure or object which includes a rigid-rod block and a
flexible-
coil block, wherein the rod-coil block copolymer forms an organized
mesostructure with
a region of one block and a region of the other block and an optical
component, wherein
the microstructure, nanostructure or object is formed as a coating on the
optical
component.
The present invention also relates to a method for producing a mesoporous
solid. This method involves providing a rod-coil block copolymer comprising a
rigid-rod
block and a flexible coil block, mixing the rod-coil block copolymer and a
selective
solvent for the flexible coil block which solubilizes that block, permitting
the rod-coil
block copolymer to self assemble into organized mesostructures with a region
of the
unsolubilized block and a region of the solubilized block, evaporating the
solvent, and
permitting the organized mesostructures to self organize into a mesoporous
solid.
Rod-coil block copolymers in a selective solvent for the coil-like polymer
self organize into hollow spherical micelles having diameters depending on the
molecular
weight and composition. Long-range, self ordering of the micelles produces
highly
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iridescent periodic mesoporous materials (i.e., photonic crystals- structures
that can create
and manipulate light signals precisely, transmitting certain wavelengths while
blocking
others). In particular, aggregation in a selective solvent for the flexible-
coil block induces
spontaneous micellization, forming thermodynamically stable large micelles (>
1 OOnm)
which after solvent evaporation produce mesoporous membrane films (Figure 12).
The
underlying mechanism which produces the periodic (ordered) mesoporous solid
film
appears to be a type of colloidal crystallization as the micellar particle
density increases
with increasing concentration due to evaporation. Further solvent evaporation
after
colloidal crystallization and lattice formation appears to be followed by
interdigitation of
the flexible coil chains of the corona layer. Investigation of the influence
of composition
and architecture on the properties of the micellar suspensions and of the
mesoporous
solids allows the tuning of the geometric and physical properties of these
self assembled
periodic mesoporous materials which may find applications such as photonic
crystals,
separation membranes. drug delivery vehicles, and scaffold for tissue
engineering.
Solution bast micellar films consist of multilayers of hexagonally ordered
arrays of spherical holes whose diameter, periodicity, and wall thickness
depend on
copolymer molecular weight and composition. Addition of guest molecules, such
as
fullerenes, into the copolymer solutions in a selective solvent for the
flexible-coil block
also regulates the microstructure and optical properties of the mesoporous
films. These
results demonstrate the potential of direct hierarchical self assembly of
macromolecular
components for engineering complex two- and three-dimensional periodic and
functional
mesostructures, without using templates or using conventional microfabrication
techniques.
Because the size, mesostructure, and properties of micellar building blocks
can be tailored through copolymer architecture and composition as well as the
solution
chemistry (McConnell et al., Phys Rev. Lett., 71:2102-2105 ( 1993); McConnell
et al.,
Macromolecules, 28:6754-6764 (1995); McConnell et al., Macromolecules, 30:435-
444
(1997); McConnell et al., Phvs. Rev. E., 54:5447-5455 (1996); Webber et al.,
Solvents
and Self Organization of Polymers, Kluwer Academic, Dordrecht ( 1996); Webber,
J.
Phvs. Chem. B, 102:2618-2626 (1998); Tuzar et al., in Surface and Colloid
Science, 15:1-
83, Plenum, New York (1993); Halperin et al., Adv. Polym. Sci., 100:31-71
(1992);
Forster et al., Adv. Mater., 10:195-217 ( 1998); Zhang et al., J. Am. Chem.
Soc.,
118:3168-3181 ( 1996); Zhang et al., Science, 268:1728-1731 ( 1995), which are
hereby
incorporated by reference), this hierarchical self assembly approach is
general for
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WO 99/47570 _ 23 - PCT/US99/05940
preparing periodic mesoporous polymeric materials. By combining different
micellar
building blocks and other colloidal particles, self assembly of very unusual
periodic
mesoscopic structures with tailorable functions is possible. In particular,
different
micellar building blocks and colloidal particles can be incorporated into the
walls of the
mesoporous solids produced by rod-coil block copolymers. Suitable micellar
building
blocks include micelles from different rod-coil block copolymers and colloidal
particles
which include dendrimers, polymer lattices, inorganic semiconductor
nanocrystals, such
as Ti02, CdS, CdSe, GaAs, and PbS, silver colloids. gold colloids. and
peizoelectric
ceramic particles. Besides photonic band gap materials and their associated
applications
(Yablonovitch, J. Opt. Soc. Am. B., 10:283-295 (1993); Joannopoulos et al.,
Nature,
386:143-145 (1997); Martorell et al., Phys. Rev. Lett., 65:1877-1880 (1990);
Miguez et
al., Appl. Ph s. Lett., 71:1148-1150 (1997), which are hereby incorporated by
reference),
the ordered micellar films and their self assembly process may have uses in
tissue
engineering and biomaterials (Fendler, Membrane Mimetic Chemistry, Wiley, New
York
( 1982), which is hereby incorporated by reference), fabrication of molecular
electronic
devices (Carter, Ed., Molecular Electronics II, Marcel Dekker, New York (
1987), which
is hereby incorporated by reference), separation media, sensors, optically
tunable and
responsive coatings, and processing of "soft" colloidal materials.
Applications are widespread for a device that selectively filters out certain
wavelengths, or colors, of light. Optical data storage and telecommunications
rely on
transmission and detection of specific wavelengths. and holographic memory
systems are
expected to do the same. The mesoporous solids of the present invention make
possible
better light-emitting diodes (LEDs), materials that are increasingly being
used to produce
more efficient lighting systems. Also possible are special paints that change
colors under
different light conditions -- perhaps lighter in the harsh glare of sunlight
and darker under
incandescent light. Another potential application: a super-efficient laser
that could
produce intense light with a fraction of the energy now required.
(Yablonovitch, J. ~Dt.
Soc. Am. B., 10:283-295 (1993), which is hereby incorporated by reference).
Yet another aspect of the present invention is a method for tissue
engineering. This method includes providing a mesoporous solid, adding a cell
culture to
the mesoporous solid, and allowing the cells to grow on the mesoporous solid
under
conditions effective to produce an organized tissue layer.
The present invention also relates to a method for producing a polymer
adsorption layer or ''brush" on a substrate. This method involves providing a
rod-coil
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block copolymer including a rigid-rod block and a flexible-coil block, mixing
the rod-coil
block copolymer and a selective solvent for one of the blocks to form a
solution of rod-
coii block copolymer and solvent, inserting a substrate into the solution,
permitting the
rod-coil block copolymer to adsorb to the substrate, and removing the
substrate from the
solution under conditions effective to form an adsorption layer of a polymer
on the
substrate.
Preferred substrates include glass, plastics, metals, semiconductors (e.g., Si
wafers with or without an oxide layer) glass coated with indium-tin-oxide
(ITO) or
aluminum or other metal, glass or plastic with a plasma treated surface, mica,
patterned
substrates, and chemical functionalized substrates.
In a preferred embodiment, the adsorption layer of a polymer is an
adsorption layer of a rigid-rod polymer block of a rod-coil block copolymer
(Figure 13).
Aggregation of the rod-coil block copolymers at surfaces produces
adsorption layers of rigid-rod polymers or so-called polymer brushes. There
are no
literature reports of rigid-rod polymer brushes, although much work has been
done in the
past 15 years on adsorption layers of flexible coil polymers (Halperin et al.,
Adv. Polvm.
Sci., 100:31-71 (1992); Tuzar et al., Surface and Colloid Science, 15:1-83
(1993); Weber
et al., Ed., Solvents and Self Or~~anization of Polymers, Kluwer Academic,
Dordrecht
( 1996); Zhang et al., Science, 272:1777-1779 ( 1996), which are hereby
incorporated by
reference). The order, precise interfaces, and self organization capability of
the rod-coil
copolymers suggest that the resulting adsorption layers (Figure 13) will have
many novel
properties of interest for adhesion and adhesives, surface modification,
fluorescent
surfaces, reflective signs/displays, waveguides, coatings, and photoregulation
of surface
properties (smart surfaces).
Another aspect of the present invention is a substrate with a polymeric
adsorption layer, wherein the adsorption layer is a rod-coil block copolymer
including a
rigid-rod block and a flexible-coil block, wherein one of the blocks of the
rod-coil block
copolymer is adsorbed to the substrate.
The present invention also relates to an optical article including a
substrate, a transparent conductor formed as a coating on the substrate, an
adsorption
layer of a polymer including a rod-coil block copolymer including a rigid-rod
block and a
flexible-coil block formed on the transparent conductor, and a coating formed
on the
surface of the adsorption layer, wherein the adsorption layer allows the
emission of
polarized light.
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Another aspect of the present invention is a method for encapsulating
guest molecules, macromolecules, or nanoparticles. This method involves
providing a
rod-coil block copolymer including a rigid-rod block and a flexible-coil
block, mixing the
rod-coil block copolymer with a selective solvent for one of the blocks which
solubilizes
that block to form a solution of rod-coil block copolymer and solvent, adding
guest
molecules, macromolecules, or nanoparticles to the solution, and permitting
the rod-coil
block copolymer to self assemble into mesostructures with a region of the
unsolubilized
block and a region of the solubilized block under conditions effective to
encapsulate the
guest molecules, macromolecules, or nanoparticles.
As used herein, guest molecules are defined as molecules deliberately
added that are not a solvent or the self assembling rod-coil block copolymer.
Guest
molecules may include oligomers which are defined as polymers including from
about 2
to about 20 repeat units.
As used herein, macromolecules are defined as polymers other than the
self assembling rod-coil block copolymer. Macromolecules are defined as
polymers
including from about 20 to about 5000 repeat units.
As used herein, nanoparticles are defined as particles ranging from about 1
nm to about 100 nm.
Preferred guest molecules, macromolecules, or nanoparticles include
fullerenes, carbon nanotubes, drug formulations, cosmetic formulations, metal
particles,
semiconductor particles, and magnetic particles. In a preferred embodiment.
the guest
molecule is a fullerene, most preferably C6o or Coo. Spherical fullerenes
(i.e., Cbo, Coo)
can be solubilized to a large degree by solutions of the rod-coil block
copolymers,
resulting in the encapsulation of large numbers 0103 to 10~°) of
fullerene molecules.
Encapsulating phenomena associated with micellar aggregates (Halperin et
al., Adv. Polym. Sci., 100:31-71 (1992); Tuzar et al., Surface and Colloid
Science, 15:1-
83 ( 1993); Weber et al., Ed., Solvents and Self Organization of Polymers,
Kluwer
Academic, Dordrecht ( 1996); which are hereby incorporated by reference) are
enhanced
in amphiphilic rod-coil block copolymers. In particular, it is possible to
package guest
molecules. macromolecules, or even nanoparticles. The reason for this is the
large size,
stability, and hollow cavity of these aggregates self organized from rod-coil
block
copolymer systems. Such an enhanced encapsulating capacity should be of
interest for
pharmaceuticals, cosmetics, detergents, lubricants, and agricultural pesticide
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formulations. (Benita, Ed., Microencansulation: Methods and Industrial
Anvlications,
Marcel Dekker, New York ( 1996), which is hereby incorporated by reference.)
Yet another aspect of the present invention is an organized mesostructure
with an encapsulated guest molecule, macromolecule. or nanoparticle which
includes a
rod-coil block copolymer including a rigid-rod block and a flexible-coil
block, wherein
the rod-coil block copolymer forms an organized mesostructure and a guest
molecule,
macromolecule, or nanoparticle, wherein the guest molecule, macromolecule, or
nanoparticle is encapsulated within the mesostructure.
Another aspect of the present invention is a method for solubilizing guest
molecules, macromolecules, or nanoparticles. This method involves providing a
rod-coil
block copolymer including a rigid-rod block and a flexible-coil block, mixing
the rod-coil
block copolymer with a selective solvent for one of the blocks which
solubilizes that
block to form a solution of rod-coil block copolymer and solvent. adding guest
molecules,
macromolecules, or nanoparticles to the solution, and permitting the rod-coil
block
copolymer to self assemble into mesostructures with a region of the
unsolubilized block
and a region of the solubilized block under conditions effective to solubilize
the guest
molecules, macromolecules, or nanoparticles.
EXAMPLES
Example 1 - Synthesis of Rod-Coil Block Copolymers
~'~laterials
Polystyrenes with mono- or di- carboxylic acid-terminated functional
group (PS-COOH, HOOC-PS-COOH), which had a molecular weight (M",) of 218400,
109200, 32760, 14200, respectively, for PS-COOH, and 54600, 27600, and 13100
for
HOOC-PS-COOH, and a polydispersity (MW/M") of 1.05 (Scientific Polymer
Products,
Inc., Ontario), were used without further purification. Reagents and solvents,
such as 4-
aminoacetophenone, dichloromethane, toluene, trifluoroacetic acid,
triethylamine,
ethanol, ethyl acetate, diphenyl phosphate were purchased from Aldrich
(Milwaukee, WI)
and were used as received. m-Cresol was distilled under vacuum before use for
the
polymerization. 5-Acetyl-2-aminobenzophenone (52) was synthesized according to
the
method disclosed in Sybert, et al., Macromolecules, 14:493-502 (1981), which
is hereby
incorporated by reference. Polyethylene oxide) (PEO) (MW of 5,000.000, M",/M"
~2.8)
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and polystyrene (MW of 6,000,000, M,~/M~ ~1.2) were purchased from
Polysciences, Inc.
(Warrington, PA) and were used as received.
Synthesis
Mono-ketone methylene-terminated polystyrene (53a).
The end group modification reactions are exemplified by the experiment
for the carboxylic acid-terminated PS with a M,Y of 32760. A rapidly stirred
solution of
100 g (3.18 mmol) of carboxylic acid terminated PS (PS-COOH) and 1.74 g (
12.84
mmol) of 4-aminoacetophenone in 500 ml of toluene was heated at reflux for 24
hours in
a 2-L flask equipped with a Dean-Stark trap. The solution was diluted with 500
ml of
toluene and 100 ml of 5 % aqueous HC1 solution was added. The organic toluene
layer
was extracted twice with 100 ml 5 % aqueous HCI solution, washed with water.
and dried
with anhydrous magnesium sulfate. The toluene was then removed and the
functionalized polystyrene was dried in a vacuum oven at 60 °C for 12
hours. The
functionalized polystyrene (53a) was purified by twice redissolving in
chloroform and
precipitating into methanol. The yield was 85%. The end groups of mono-
functionalized
PS (PS-COOH) with a MW of 218400, 109200, and 14200, were similarly converted
to
ketone methylene functional units.
Diketone methylene-terminated polystyrene (53b).
The end group modification reactions are exemplified by the experiment
for the dicarboxylic acid-terminated PS with M,~ of 54,600. A rapidly stirred
solution of
100 g ( 1.83 mmol) of dicarboxylic acid-terminated PS (HOOC-PS-COOH, M,~. _
X4,600)
and 2.0 g (7.33 mmol) of 4-aminoacetophenone in S00 mL of toluene was heated
at reflux
for 24 hours in a 2-L flask equipped with a Dean-Stark trap. The reaction
solution was
diluted with 500 mL of toluene and 100 mL of 5 % aqueous HCl solution was
added.
The organic toluene layer was extracted twice with 100 mL of 5 % aqueous HCI
solution,
washed with water, and dried with anhydrous magnesium sulfate. The toluene was
then
removed by rotary evaporator and the functionalized polystyrene was dried in a
vacuum
oven at 60 °C for 12 hours. The functionalized polystyrene (53) was
purified by twice
redissolving in chloroform and precipitating into methanol. The yield was 85
%. The
end groups of di-functionalized PS (HOOC-PS-COOH) with M« of 27600 and 13100
were similarly converted to diketone methylene functional units.
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Poly(phenylquinoline)-b-polystyrene diblock copolymers (54).
PPQ-b-PS block copolymers (PPQ;o-b-PSzooo, PPQso-b-PSiooo, PPQso-b-
PS3oo~ PPQso-b-PSi3o, PPQio-b-PSiooo, PPQ~o-b-PS3oo, and PPQio-b-PS~3o (54a-
54g)) were
synthesized by copolymerization of 5-acetyl-2-aminobenzophenone (52) with PS-
CONH-
Ph-COCH3 (53a) as shown in Figure 5. The copolymerization is exemplified by
the
I 0 preparation of PPQ;o-b-PS3oo (54c), as follows. 2.39 g ( 10 mmol) of 5-
acetyl-2-
aminobenzophenone (52) and 6.31 g (0.2 mmol) of PS-CONH-Ph-COCH3 (53a) were
added to a solution of 5 g of diphenyl phosphate (DPP) and 20 g of freshly
distilled m-
cresol in a cylindrical glass flask fitted with a mechanical stirrer, two gas
inlets, and a side
arm. The reactor was purged with argon for 10 minutes before the temperature
was raised
slowly to 140 °C in 2-3 hours. As the viscosity of the reaction mixture
increased with
time, small amounts of DPP were added, until a total of 20 g of DPP was
reached. The
reaction was maintained at 140 °C for 48 hours under argon. The bright
orange solution
product was cooled and precipitated into 500 mL of 10% triethylamine/ethanol
mixture.
The final product was purified by soxlet extraction with 10%
triethylamine/methanol for
48 hours to get rid of the residue m-cresol, DPP, and the un-reacted
homopolymer PS,
because homopolymer PS can dissolve in hot methanol. The degree of
polymerization of
the PPQ block (NA) in the rod-coil diblock (ANABNB) was controlled by the
stoichiometric
method. Because the condensation reaction yields of copolymerization were
100%, the
polydispersity (M,~/M") of the PPQ blocks was estimated to be around the
theoretically
expected value of 2 (Odian, Principles of Polymerization, 2nd ed.. Wiley, New
York,
Chapters 1 and 2 ( 1981 ), which is hereby incorporated by reference). 54c:
Yield: 100%, '
H NMR (C6D;N02) 8: 1.5-1.6 (m, 2x300H), 2.2 (s, Ix300H), 6.7-6.8 (d, 2x300H),
7.3-
7.4 (m, 3x300H), 7.5 (m, Sx50H), 8.9 (d, 1x50H), 9.2 (s, IxSOH), 9.4-9.6 (d,
Ix50H), 9.7
(s, 1x50H). FTIR (NaCI disc, cm ~): 3060, 3025, 2920. 2850, 1677, 1600, 1492,
1451,
1346. 1204, 1180, I 134, 1028, 756, 698.
The diblock copolymers of PPQ;o-b-PS2ooo (54a), PPQ;o-b-PS~ooo (54b), PPQ;o-b-
PS i 30 (54d), PPQ i o-b-PS, o00 (54e), PPQ i o-b-PS3oo (54f7, and PPQ, o-b-PS
i 30 (54g) were
similarly prepared. 54a: Yield: 100%. ' H NMR (C6D;N02) 8: I .5-I .6 {m,
2x2000H), 2.2
(s, 1 x2000H), 6.7-6.8 (d, 2x2000H), 7.3-7.4 (m, 3x2000H), 7.5 (m, Sx50H}, 8.9
(d,
1 xSOH), 9.2 (s, 1 x50H), 9.4-9.6 (d, 1 x50H), 9.7 (s, 1 x50H). FTIR (NaCI
disc, cm-'}: 3060.
3025, 2920, 2850, 1677, 1600, 1492, 1451, 1346, 1204, 1180, 1134, 1028, 756,
698. 54b:
Yield: 100%, ' H NMR (C6D;N02) 8: 1.5-1.6 (m, 2x 1 OOOH), 2.2 (s, 1 x 1 OOOH),
6.7-6.8
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WO 99/47570 - 29 - PCTNS99/05940
(d, 2x 1 OOOH), 7.3-7.4 (m, 3x I OOOH), 7.5 (m, 5x50H), 8.9 (d, 1 x50H), 9.2
(s. 1 x50H), 9.4-
9.6 (d, 1x50H), 9.7 (s, 1x50H). FTIR (NaCI disc, crri'): 3060, 3025, 2920,
2850, 1677,
1600, 1492, 1451, 1346, 1204. 1180. I 134, 1028, 756, 698. 54d: Yield: 100%, ~
H NMR
(C6D;NOz) 8: 1.5-1.6 (m, 2x130H), 2.2 (s, 1x130H), 6.7-6.8 (d, 2x130H), 7.3-
7.4 (m,
3x I30H), 7.5 (m, 5x50H), 8.9 (d: 1 x50H), 9.2 (s, I x50H), 9.4-9.6 (d, I
x50H), 9.7 (s,
IxSOH). FTIR (NaCI disc, cm''): 3060, 3025, 2920, 2850, 1677, 1600, 1492,
1451, 1346,
1204, 1180, 1134, 1028, 756, 698. 54e: Yield: 100%, ~ H NMR (CbD;NOz) 8: 1.5-
1.6 (m,
2x 1 OOOH), 2.2 (s, I x I OOOH), 6.7-6.8 (d, 2x 1 OOOH), 7.3-7.4 (m, 3x 1
OOOH), 7.5 (m,
5x 1 OH), 8.9 (d, 1 x 1 OH), 9.2 (s, 1 x I OH), 9.4-9.6 (d, 1 x 1 OH), 9.7 (s,
1 x 1 OH). FTIR (NaCI
disc, cm''): 3060, 3025, 2920, 2850, 1677, 1600, 1492, 1451, 1346, 1204, I
180, 1134,
1028, 756, 698. 54f: Yield: 100%, ~ H NMR (C6D;NOz) 8: 1.5-1.6 (m, 2x300H),
2.2 (s,
1 x300H), 6.7-6.8 {d, 2x300H), 7.3-7.4 (m, 3x300H), 7.5 (m, 5x i OH), 8.9 (d.
1 x 1 OH), 9.2
(s, 1 x 1 OH), 9.4-9.6 (d, 1 x I OH), 9.7 (s, 1 x I OH). FTIR (NaCI disc,
cm''): 3060. 3025, 2920,
2850, 1677, 1600, 1492, 1451, I 346, 1204, I i 80, I 134, 1028, 756, 698. 54g:
Yield:
100%, ~ H NMR (C6D;NOz) 8: 1:5-1.6 (m, 2x130H), 2.2 (s, 1x130H), 6.7-6.8 (d,
2x 130H), 7.3-7.4 (m, 3x 130H), 7.5 (m, 5x 1 OH), 8.9 (d, 1 x 1 OH), 9.2 (s, I
x 1 OH), 9.4-9.6
(d, 1 x 1 OH), 9.7 (s, I x 1 OH). FTIR (NaCI disc, cm''): 3060, 3025, 2920,
2850. 1677, I 600,
1492, 1451. 1346, 1204, 1180, I 134, 1028, 756, 698.
Poly (phenylquinoline)-b-polystyrene-b-poly(phenylquinoline) triblock
copolymers {55).
PPQ-b-PS-b-PS triblock copolymers (PPQ;o-b-PS;oo-b-PPQ;o, PPQ;o-b-
PSz;o-b-PPQ;o, and PPQ;o-b-PSlzo-b-PPQ;o (55a-c)) were synthesized by block
copolymerization of 5-acetyl-2-aminobenzophenone (52) with 53b (CH3C0-Ph-NHCO-
PS-CONH-Ph-COCH3), as shown in Figure 6. The copolymerization is exemplified
by
the preparation of PPQ;o-b-PS;oo-b-PPQ;o (55a), as follows. 2.39 g (I O mmol)
of 52 and
5.20 g (0.1 mmol) of 53b (Mw 54600) were added to a solution of 5 g of
diphenyl
phosphate (DPP) and 20 g of freshly distilled m-cresol in a cylindrical glass
flask fitted
with a mechanical stirrer, two gas inlets, and a side arm. The reactor was
purged with
argon for 10 minutes before the temperature was raised slowly to 140 °C
in 2-3 hours. As
the viscosity of the reaction mixture increased with time, small amounts of
DPP were
added, until a total of 20 g of DPP was reached. The reaction was maintained
at 140 °C
for 48 hours under argon. The bright orange solution product was cooled and
precipitated
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into 500 mL of 10 % triethylamine/ethanol mixture to wash away the m-cresol
and DPP.
The final product was purified by Soxlet extraction with 10 %
triethylamine/methanol for
48 hours to get rid of the residue m-cresol, DPP, and the un-reacted
homopolymer PS,
because homopolymer PS can dissolve in hot methanol. The degree of
polymerization of
the PPQ block (NA) in the rod-coil triblock copolymers (ANABNBANA) was
controlled by
the stoichiometric method. Because the condensation reaction yields of
copolymerization
were 100%, the polydispersity (MW/M") of the PPQ blocks was estimated to be
around the
theoretically expected value of 2. 55a : Yield: 100%. ~ H NMR (C6D;N0~) 8: 1.5-
I .6 (m,
2x500H), 2.2 (s, 1 x500H), 6.7-6.8 (d, 2x500H), 7.3-7.4 (m, 3x500H), 7.5 (m,
Sx I OOH),
8.9 (d, 1 x 1 OOH), 9.2 (s, 1 x 1 OOH), 9.4-9.6 (d, 1 x 1 OOH) , 9.7 (s, 1 x 1
OOH). FTIR (NaCI
dics, cm-'): 3060. 3025, 2920, 2850, 1677, 1600, 1492, 1451, 1346, 1204. I
180. 1134,
1028, 756, 698.
The copolymers of PPQ;o-b-PS~;fl-b-PPQ;o (55b) and PPQ;o-b-PS,2o-b-
PPQ;o (55c) were similarly synthesized. 55b: Yield: 100%, ~ H NMR (C6D;N0~)
8: I.5-1.6 (m, 2x250H), 2.2 (s, 1x250H), 6.7-6.8 (d, 2x250H), 7.3-7.4 (m,
3x250H), 7.5
(m, Sx 1 OOH), 8.9 (d, 1 x 1 OOH), 9.2 (s, 1 x 1 OOH), 9.4-9.6 (d, 1 x 1 OOH)
, 9.7 (s, I x 1 OOH).
FTIR (NaCI disc. cm'): 3060, 3025, 2920, 2850, 1677, 1600, 1492, 1451, 1346,
1204,
1180, 1134. 1028, 756, 698. 55c: Yield: 100%, ~ H NMR (C6D;N0~) 8: I .5-1.6
(m,
2x 120H), 2.2 (s, I x 120H), 6.7-6.8 (d, 2x 120H), 7.3-7.4 (m, 3x 120H), 7.~
(m, ~x 1 OOH),
8.9 (d, 1 x 1 OOH), 9.2 (s, 1 x 100H), 9.4-9.6 (d, 1 x I OOH), 9.7 (s, 1 x 1
OOH). FTIR (NaCI disc,
cm-'): 3060, 3025, 2920, 2850, 1677, 1600, 1492. 1451, 1346, 1204, I 180,
1134, 1028.
756, 698.
Example 2 - Characterization of Block Copolymers
Thermogravimetric analysis (TGA) and differential scanning calorimetry
(DSC) were done on a DuPont Model 2100 Thermal Analyst based on an IBM PS/2
Model 60 computer and equipped with a Model 951 TGA unit and a Model 910 DSC
unit. The DSC thermograms were obtained in nitrogen at a heating rate of
5°C/minute.
The TGA data were obtained in flowing nitrogen at a heating rate of
10°C/minute. ~H
NMR spectra were taken at 300 MHz, using a General Electric Model QE 300
instrument.
Block copolymer solutions for ~H NMR spectroscopy were prepared in a dry box,
using
deuterated nitrobenzene(C6D;N02) containing gallium chloride. Fourier
transform
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S infrared (FTIR) spectra were taken at room temperature using a Nicolet 20SXC
FTIR
spectrometer under nitrogen purge. Samples were either free-standing films or
films
coated on NaCI disks. The FTIR spectra of the parent PPQ and PS homopolymers
were
obtained as the free standing films from formic acid and dichloromethane
solutions,
respectively, whereas the spectra of the rod-coil block copolymers were
obtained from
films coated on NaCI disks. The free standing films were prepared by removing
films
spin-coated on glass using a sharp razor blade after soaking the films in
water for 12
hours.
Samples for observation by polarized optical microscopy (POM) and
fluorescence microscopy (FM) were prepared by allowing several drops of a
block
copolymer solution in TFA:DCM or TFAaoluene to spread and dry on glass slides.
The
various drying conditions explored are described below and were found not to
influence
the observed morphologies of aggregates (size, shape, and their
distributions).
Observations were done on an Olympus Model BXbO Fluorescence Optical
Microscope.
The glass slides were placed under an optical fluorescence microscope. Optical
(bright
field, polarized light) and fluorescence images were recorded by a digital
camera with 0.5
inches CCD chips. The images were stored and processed by a PC computer
equipped
with Image Pro. (Media Cybernetics, Silver Spring, MD) software.
Samples for scanning electron microscopy (SEM) were prepared by
allowing several drops of a copolymer solution to spread and dry on aluminum
substrates.
The samples were then coated with a thin layer of 100 ~ gold.
Films of solid aggregates were too scattering in the visible light region to
obtain normal optical absorption spectra. Dilute solution optical absorption
spectra of the
copolymer samples and those of thin films of block copolymers dispersed (0.1
wt%) in
poly (ethylene oxide) (PEO) were recorded on a Perkin-Elmer Model Lambda 9
UV/VIS/NIR Spectrophotometer at room temperature. For the measurements
performed
on solutions, the solutions were sealed inside 1-mm-path-length quartz cuvet
to prevent
solvent evaporation.
Photoluminescence (PL) and photoluminescence excitation (PLE) spectra
were obtained on a Spex Fluorolog-2 spectrofluorimeter. Time-resolved
fluorescence
spectra were obtained by using a single-photon-counting technique. The
solutions of the
aggregates were similarly sealed inside a 1-mm-path-length quartz cuvet. Thin
films and
solutions of aggregates were measured by using the front face geometry in
which samples
were positioned such that the emission was detected at 22.5° from the
incident radiation
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S beam. Further details of the photophysical experimental techniques used here
are similar
to those we have described in detail elsewhere (Osaheni et al., J. Am. Chem.
Soc.,
117:7389-7398 ( 1995), which is hereby incorporated by reference).
Example 3 - Aggregation Experiments
Self assembly of aggregates of the rod-coil block copolymers described in
Example 1 was done using various ratios of trifluoroacetic acid
(TFA)/dichloromethane
(DCM) and TFA/toluene, which are good selective solvents for the rigid-rod
block. In
these mixed solvents, the rigid-rod PPQ block was protonated and solvated by
the TFA,
forming a rod-like polyelectrolyte block in solution. Drying drops of dilute
solutions (0.5
to 1.0 mglml) of PPQ-b-PS on substrates produced micelle-like aggregates
because DCM
and toluene, which are selective solvents for the PS block, had faster
evaporation rates
than TFA which is a selective solvent for the rigid-rod block. In contrast.
thin films of
the rod-coil block copolymers similarly prepared from nitrobenzene/GaCl3
solutions (0.5
to 1 mg/ml), i.e., solutions in a nonselective solvent. did not reveal any
characteristic
aggregate morphology under optical microscopy. These results suggested that
block
selective solvents facilitated the self assembly of the amphiphilic rod-coil
block
copolymers. Films (~l to 20 p,m thick) resulting from drying dilute solutions
of the
copolymers or copolymer/solubilized fullerenes on glass slides or aluminum
substrates at
room temperature (or at high temperature. 95 °C) were investigated as
made. or after
treating them in 5% triethylamine/ethanol (to remove any trace acids) and
drying in a
vacuum oven at 60 °C for 24 hours, or after heating to 200 °C
for one hour (to ensure
complete solvent evaporation). The films were investigated by SEM, POM. and FM
microscopies as well as by photoluminescence (PL) spectroscopy. No difference
in
morphology was observed in the various film samples treated differently after
drying.
However. the dominant morphology prepared from a particular diblock copolymer
was
highly dependent on the ratio of TFA:DCM or TFAaoluene of the mixed solvent
used.
These solid aggregates, when placed in a fresh clear TFA:DCM or TFAaoluene
solvent
mixtures. redissolved in solution and spontaneously re-assembled into
aggregates
corresponding to that particular solvent mixture. Such an easy dissolution of
solid
aggregates and subsequent re-aggregation indicated the thermodynamic stability
and
equilibrium nature of the aggregates formed by diblock and triblock
copolymers.
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For real time optical microscopy observations, the dilute copolymer
solutions (0.001 to 0.1 wt.%) were sealed inside 6 mm x 50 mm glass tubes.
Periodic
examinations of these dispersions showed that the aggregates were extremely
robust and
were stable in solution.
Dilute solutions (0.5 to 1.0 mg/ml) of each rod-coil block copolymer in
mixed solvents, TFA:DCM or TFAaoluene at various volume ratios, were used for
aggregation studies. Because TFA is a good solvent for PPQ block and
protonates its
imine nitrogens, whereas the PS block is insoluble in it, micelle-like
aggregates (Figure 7)
resulted from manipulating the solvent composition. In TFA solvent. PPQ blocks
essentially were transformed to polyelectrolytes with positive charges. The
electrostatic
forces between protonated PPQ blocks and the surrounding negative counter-ions
were
expected to help stabilize the colloidal structures, just as the charged
protein helps
stabilize the natural rubber latex. By adding various amount of DCM, which is
a
selective solvent for PS, to TFA, the polarity and acidity of the solvent
mixtures could
easily be controlled, thus varying the strength of the hydrogen-bonding,
electrostatic
forces, and solvophobic effects. The hydrogen-bonding and electrostatic forces
increased
with the decrease in polarity, whereas the solvophobic effects had just the
opposite
relationship. For diblock copolymers, micelle-like aggregates can be expected
(Figure
14) to result from manipulating the solvent composition. The expected
structure of such
an aggregate in the TFA solution is an inner PS block surrounded by the
protonated PPQ
shell. This basic aggregate structure is expected to be retained in the solid
state after
solvent evaporation, which also deprotonates the PPQ block (Figures 7 and 14).
Rod-
coil-rod triblock copolymers can either fold to form single loop-layers, or
they can form
biiayer tape-like structures as shown in Figure 14. Therefore, in selective
solvents for the
rigid rod blocks, triblock copolymers are expected to either form micelles
from single
loop-layers as diblock copolymer did, or form vesicles from bilayer tape-like
structures
(Figure 14). The self assembly of a rod-coil block copolymer in a selective
solvent for
the rigid-rod block has not been theoretically investigated (Semenov et al.,
Sov. Phys.
JETP, 63:70-79 ( I 986); Sem~nov, Mol. Crust. Liq. Crest., 209:191- I 99 (
1991 ); Halperin,
Macromolecules, 23:2724-2731 ( I 990); Halperin, Europhys. Lett., 10:549-553 (
1989);
Williams et al., Macromolecules, 25:3561-3568 (1992); Raphael et al.,
Makromol.
Chem., Macromol. Symn., 62: I -17 ( I 992), which are hereby incorporated by
reference)
but is experimentally accessible here because of the differential solubility
of PPQ and PS
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blocks. Self assembly of discrete aggregates of the rod-coil block copolymers
did not
occur from solutions in non-selective solvents, such as nitromethane
containing GaCl3.
Four different, micelle-like aggregate morphologies were observed in
PPQso-b-PS3oo (54c) by OM, FM. and SEM: spheres, lamellae, cylinders. and
vesicles
(Figures 15 and 16). The main factors determining morphology were the initial
solvent
composition (TFA:DCM ratio) arid the solution drying rate. The cylindrical
aggregates
were obtained from highly polar solvents with TFA/DCM ratio of 9/1. They were
relatively uniform in diameter (1 to 3 Vim) but highly poIydisperse in length
(5 to 25 p.m),
coexisting with minor phase-spherical aggregates. Spherical aggregates with a
wide
distribution of sizes, typically 0.5 to 10 pm diameters, were observed by
rapid drying of
solutions on a heated substrate at 95 °C and by preparing aggregates
from solutions from
a TFA/DCM ratio of 4/l . Further reducing the TFA/DCM ratio resulted in two
more
phases. Relatively flat (2D) lamellae with rough surfaces having diameters in
the range
of 5 to 30 ~m together with minor phase-donut-shape rings (< 20%) were
obtained from a
solution with a solvent ratio of 1:1. Further reducing the solvent ratio to
1/4 led to
predominantly (~80%) donut-shape rings, with outer diameters of about 0.5 to
1.0 um and
wall thickness of about 200 nm, coexisting with a minor phase of lamellae. All
these four
morphologies had highly ordered structures with crystalline feature, as
evidenced by
Figures 16A and 16C, which were taken under cross-polarizers. In Figure 16D,
the
hollow microcavity and closed ends of the cylindrical aggregates were
revealed.
Aggregates prepared by drying solutions at room temperature had non-spherical
morphologies, and each sample was predominantly (~70%) either lamellae,
cylinders, or
vesicles depending on the initial solvent composition; the minor phases in
these
morphologies were cylinders, lamellae, or spheres, respectively. Lamellar
aggregates had
diameters in the 5 to 30 ~m range, the cylinders were relatively uniform in
diameter (1 to
3 pm) but highly polydisperse in length (5 to 25 Vim), and vesicles had outer
diameters of
about 0.5 to 1.0 ~m and wall thickness of about 200 nm. Similar multiple
morphologies
were observed in aggregates prepared from other diblock copolymers, with
average sizes
of the aggregates depending on the molecular weight of the block copolymers
(Table 1 ).
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Table 1. Typical morphologies from diblock and triblock copolymers, and their
sizes.
Copolymer NA-NB or NA-Ns-NA- Morphology
Type Size (gym)
54a 50-2000 Spherical I-40 (10)
Lamellar 40
54b 50-1000 Spherical I-20 (8)
Cylindrical Diameter of 2 ~m
Lamellar 30
Ring Outer diameter 2pm
54c 50-300 Spherical I-10 (4)
Cylindrical Diameter of I p.m
Lamellar 20
Ring Outer diameter 1 ~tm
54d 50-130 Spherical 1-5 (2)
Cylindrical Diameter of 0.8 p.m
Lamellar 10
Ring Outer diameter 0.8 wm
54e 10-1000 Spherical 1-10 (4)
Cylindrical Diameter of 1 ~m
Lamellar 20
Ring Outer diameter 1 um
54f 10-300 Spherical 0.5-5 (3)
Cylindrical Diameter of 0.5 pm
Lamellar 10
Ring Outer diameter 0.5 pm
54g 10-130 . Spherical 1-10{1}
Lamellar 8
55a 50-500-50 Spherical 0.5-200 (27)
55b 50-250-50 Spherical - 0.5-80 ( 16)
55c 50-120-50 Spherical 0.5-15 (2)
w i ne numoer lnsiae nracxet is the average sizes.
Figure 17 shows some representative morphologies self assembled from copolymer
54b
(Figures 17A and I7B), 54e (Figure 17C), 54f (Figures 17D), and 54g (Figures
17E and
I7F). Spherical aggregates with sizes ranging from 1 - 20 p.m were obtained
from PPQ;o-
b-PS~ooo (54b, Figure 17A), which was bigger than those from PPQ;o-b-PS3oo
(54c) by a
factor of about 2 (Figures 16A and B). Cylindrical aggregates prepared from
PPQ;o-b-
PSiooo (54b. Figure 17B) had a diameter of 2 ~tm, and length of 2-20 p,m, with
diameter
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about twice the size of cylinders prepared from PPQ;o-b-PS3~ (54c). Therefore,
the
higher the molecular weight, the bigger the average sizes of the aggregates.
This trend
was more clearly shown in Figures 17C to 17F. The lamellae prepared from PPQ,o-
b-
PS ~o~ (54e) had sizes in the ranges of 20-30 Vim, the sizes were reduced to
10-1 S ~m for
PPQ,o-b-PS3~ (54fj, and further down to 5-8 ~m for PPQ,o-b-PS,3o (54g). All
these
aggregates had highly ordered structure, as evidenced by Figure 17E, which was
taken
under cross-polarizers. These observations were consistent with theoretical
prediction
that morphologies of the aggregates change with the varying molecular weight
(Radzilowski et al., Macromolecules, 26:879-882 (1993); Radzilowski et al.,
Macromolecules, 27:7747-7753 (1994); Wadawski et al., Nature, 369:387 et seq.
(1994);
Chen et al., Science, 273:343-346 (1996); Chen et al., Macromolecules, 28:1688-
1697
(1995), which are hereby incorporated by reference).
Repeated heating of the aggregates to 200 °C. which is above the
glass
transition (T') of PS blocks (To = 100 °C) and below that of PPQ blocks
(To >350 °C)
{Sybert et al., Macromolecules, 14:493-502 ( 1981 ); Agrawal et al.,
Macromolecules,
26:895-905 (1993); Agrawal et al., Chem. Mater., 8:579-589 (1996), which are
hereby
incorporated by reference), did not have any effect on the aggregate
morphologies, which
demonstrated the robustness of these aggregates. Also, the polydispersity of
the rigid-rod
block apparently had no discernible effect on the aggregate morphologies.
Compared to recently observed multiple morphologies in coil-coil block
copolymers (Zhang et al., Science, 272:1777-1779 { 1996); Zhang et al.,
Science,
268:1728-1731 (1995); Zhang et al., J. Am. Chem. Soc., 118:3168-3181 (1996),
which
are hereby incorporated by reference), the present aggregates were larger by
about two
orders of magnitude.
The unusually large sizes of the spherical and cylindrical aggregates,
unlike bilayer vesicles and lamellae that could in principle grow to any size
(Figure 18),
could not be explained by a simple core-shell structure of conventional block
copolymer
micelles (Halperin et al., Adv. Polvm. Sci., 100:31-71 (1992); Tirrell, in
Weber et al.,
Eds., Solvents and Self Organization of Polymers, Kluwer Academic, Dordrecht,
pp.281-
308 (1996); Tuzar et al., Surface and Colloid Science, 15:1-83 (1993); Weber
et al., Eds.,
Solvents and Self Organization of Pol, mers, Kluwer Academic, Dordrecht,
(1996); Gast,
in Weber et al., Eds., Solvents and Self Or~,anization of Pol~, Kluwer
Academic,
Dordrecht, pp. 259-280 ( I 996); Vagberg et al., Macromolecules. 24:1670-1677
( 1991 );
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Semenov et al., Sov. Phys. JETP, 63:70-79 ( 1986); Semenov, Mol. C s~q.
Cryst.,
209:191-199 ( 1991 ); Halperin, Macromolecules, 23:2724-2731 ( 1990);
Halperin,
Europhvs. Lett., 10:549-553 (1989); Williams et al., Macromolecules, 25:3561-
3568
(1992); Raphael et al., Makromol. Chem.. Macromol. Symn., 62:1-17 (1992);
Zhang et
al., Science. 272:1777-1779 (1996); Zhang et al., Science, 268:1728-1731
(1995); Zhang
et al., J. Am. Chem. Soc., 118:3168-3181 ( 1996), which are hereby
incorporated by
reference). The main difficulty was that the rod-coil block copolymer chains
from which
the aggregates were assembled had on average fully extended lengths of at most
500 nm
for PPQ;o-b-PS~ooo (54a), and much less for the others, e.g., 100 nm for PPQ;o-
b-PS3oo
(54c). From x-ray diffraction data on oligoquinolines the repeat unit length
of PPQ is
0.64 nm. The repeat unit length of extended chain PS was estimated to be 0.226
nm.
Therefore. the maximum extended chain lengths of PPQ;o-b-PS3oo (54c) and PPQ,o-
b-
PS3oo (~4~ would be 100 and ~74 nm, respectively. Spherical and cylindrical
aggregates of about 200 nm diameter would thus be expected if solid PS-
core/PPQ-shell
assemblies were formed for PPQ;o-b-PS3oo (54c). In contrast, the observed
aggregates
were about 10 to 50 times larger (Figures 15-17). To account for the size
difference, the
observed spherical and cylindrical aggregates were thought to form large
hollow cavities.
An aggregate structure in accord with this hypothesis is cavity-core/PS-inner
shell/PPQ-
outer shell (Figure 7 and 14). For a typical 5-~m diameter spherical
aggregate, 89% of its
total volume of 65 pm3 would be empty. The driving force for the large size
and hollow
cavity of these aggregates appeared to be a more efficient packing of the
rigid-rod blocks
and, consequently, a more ordered and stable aggregate structure. All the
different
aggregates under cross-polarizers showed that they were highly ordered with
crystalline
features. The aggregation number, N°, or number of rod-coil block
copolymer chains per
aggregate, was estimated to be 1.5 x 108 for a hollow sphere with diameter of
S p,m,
assuming the density of the spherical aggregates is 0.14 g/cm3. The
aggregation number
for cylindrical aggregates with diameter of 1 p.m and length of 10 pm was
similarly
estimated to be 3x108. The aggregation number N° can also be estimated
by the amount
of the copolymers consumed for construction of various aggregates. For
example. about
2x10' discrete spherical aggregates/mm' was measured from a photomicrograph
taken
from a I-mg diblock copolymer PPQ;o-b-PS3oo (54c) covering a total area of 5
cm'.
Thus, one gets 2.4x10-~6 mole diblock/aggregate (or 10-g mg diblock/aggregate)
or No =
1.5x108. Similar procedures for cylindrical aggregates gave
2x104aggregates/mm' from a
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photomicrograph taken on a 0.2-mg diblock copolymer PPQSO-b-PS3~ (54c)
covering a S-
cm2 area. From this, one gets 4.8x10-~5 mole diblock/aggregate or N° =
3x108. The
aggregation numbers estimated by these two different methods were in perfect
agreement.
Aggregate luminescence of the diblock copolymers (54a-548) and the
triblock copolymers {55a-55c) was explored as a means of probing the molecular
packing
of the luminescent rigid-rod PPQ blocks in the different aggregate
morphologies.
Different photoluminescence (PL) emission and excitation (PLE) spectra were
observed
for spherical, lamellar, and cylindrical aggregates self assembled from
diblock
copolymers 54a-548 (54c, Figure 19) and vesicles from triblock copolymer 55a-
55c. For
comparison, PLE and PL spectra of PPQ homogeneously dispersed in poly(ethyl
oxide)
(PEO) matrix (0.1 wt.%) were also obtained. (Table 2)
Table 2. Photophysical parameters of aggregates from diblock and triblock
copolymers.
Copolymer PPQ/PEO Diblock Triblock
copolymers
3a-3g
/polymer Single-chainsphericalcylindricallamellarRind-likecopolymers
SSa-
SSc
PL ~.maX 460 454 594 576 580 610
(nm)
PLE ~mex 390 388 406, 406, 406, 406, 422,
(nm) 422, 422, 422, 475
460 460 460
Lifetime 1.1 0.93 0.38 0.34 0.35 0.36
(z,)
Lifetime 4.7 - 3.5 2.6 2.~ 2.8
(T,)
The PL spectrum of PPQ/PEO solid solution gave rise to an emission band
centered at
460 nm, which was assigned to PPQ single-chain emission. The corresponding PLE
spectrum, when monitored at 460 nm, gave rise to an absorption band centered
at 390 nm,
which was identical to the absorption spectrum obtained from UV-vis
experiments.
Spherical aggregates from diblock copolymers exhibited a blue emission band
centered at
4S4 nm, whereas the PLE spectrum showed an absorption band with a peak at 388
nm,
slightly blue-shifted to the emission from the PPQ single chain. In contrast,
both lamellar
and cylindrical aggregates from diblock and vesicles from triblock copolymers
had broad
emission bands with peaks at 576, 594 nm, and 610nm, respectively, and PLE
spectra of
those when monitored at emission peaks gave rise to spectra which were totally
different
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WO 99/47570 - 39 - PCT/US99/05940
to the PLE spectrum of PPQ/PEO solid solution. The PLE spectra showed a peak
at 422
nm and a shoulder peak at 406 nm and 460 nm. The extensive morphology studies
of
aggregates revealed that all the aggregates had highly ordered crystalline
structures
(Figures 16, 17, 20, and 21 ), suggesting that in all these aggregates. a high
degree of
ordered packings of PPQ blocks took place. Therefore, the PL and PLE spectra
showed
that the PPQ blocks in spherical aggregates self assembled from diblock
copolymers
formed H-aggregates, whereas the PPQ blocks in cylindrical, lamellar, donut-
ringlike
aggregates from diblock copolymers and vesicles from triblock copolymers
formed J-
aggregates (Shimomura et al., J. Am. Chem. Soc., 109:5175-5183 ( 1987), which
is hereby
incorporated by reference). The slight differences in PL and PLE spectra of
the J-
aggregates could be caused by the differences in tilted angles of the PPQ
blocks (Figure
22). The different molecular packing of PPQ blocks in the spherical. lamellar
and
cylindrical aggregates from diblock together with vesicles form triblock was
confirmed
by the time-resolved PL studies (Figure 19). Time-resolved PL decay dynamics
of the
fluorescent PPQ block in the different aggregate morphologies evidenced
different
excited-state lifetimes (Figures 19 and 23B). Compared to the PPQ dilute solid
solution,
which exhibited two lifetimes ( 1.1 and 4.7 ns), the PL decay dynamics of PPQ
blocks in
the spherical aggregates from diblock copolymer was approximately described by
a single
lifetime of 0.93 ns. However, in the lamellar and cylindrical aggregates and
vesicles,
biexponential lifetimes of 0.38 and 3.5 ns, 0.34 and 2.6 ns, and 0.36 and 3.0
ns,
respectively, best fit the decay dynamics. These results suggested that the
observed
morphology-dependent emission properties of the block copolymer aggregates
reflected
the varying molecular packing of the fluorescent rigid-rod blocks.
SEM microscopy was used to confirm the proposed structures of the
spherical and cylindrical aggregates and provide additional information of the
large cavity
inside the aggregates. Figure 24 shows the SEM of the spherical aggregates
from diblock
copolymer 54c (Figures 24A, 24B, 24E, 24F) and 54f (Figures 24C, 24D) prepared
from
TFA/DCM (7/1, v/v) solutions with copolymer concentration of 0.~ wt.%.
Spherical
aggregates with wide size distribution, with size in the range of 1-10 p.m
were observed
for copolymer 54c, whereas the spherical aggregates from 54f had typical sizes
in the
range of 0.5-5 p.m. These spherical aggregates had a very smooth surface and 3-
D
spherical shapes. Figure 24E shows a spherical aggregate prepared from
copolymer 54c
with a defect hole, and the magnified version of defect area of Figure 24E is
shown in
CA 02324140 2000-09-15
WO 99/47570 - 40 - PCTNS99/05940
Figure 24F. That the spherical aggregate is indeed hollow inside and can be
seen clearly,
consistent with the proposed model for the spherical aggregates.
Fluorescence photomicrographs (Figures 25 and 26) confirmed the
aggregate sizes and shapes observed in OM and SEM for the diblock copolymers
and
revealed that the fluorescent rigid-rod blocks were located at the outer
shells of the
aggregates, as depicted in the model of Figure 7. The hollow microcavity and
closed
ends of the cylindrical aggregates were also revealed (Figure 25C). The entire
---200 nm
bilayer thickness of each vesicle appeared to fluoresce because the 140 nm
separation
between the PPQ blocks in the bilayers was below the resolution limit (Figure
25D).
Also, because of three-dimensional (3-D) symmetry and uniformity of emission,
the
microcavity of the spherical aggregates could not be directly observed (Figure
25A) but
could be inferred from that of similarly formed cylinders (Figure 7). The 3-D
nature of
the spherical aggregates could be clearly distinguished from the relatively
flat (2-D)
lamellae, which have rough surfaces. Figure 26 shows the fluorescence
photomicropraphs of typical aggregates, revealing remarkably clear images of
large
micellar aggregates (spheres, lamellae, cylinders) by virtue of the intrinsic
fluorescence of
the rod-like block. These self assembled nonbiological aggregates were in the
size range
(albeit not the complexity) of cellular biology. Furthermore, they had well-
defined 3-D
shape and were larger than micelles from conventional surfactants and coil-
coil block
copolymers by factors of 100 and 5000, respectively (Halperin et al., Adv.
Polvm. Sci.,
100:31-71 (1992); Tuzar et al., Surface and Colloid Science, 15:1-83 {1993);
Weber et al.,
Ed., Solvents and Self Organization of Polymers, Kluwer Academic, Dordrecht (
1996);
Zhang et al., Science, 272:1777-1779 ( 1996); Chen et al., Science, 273:343-
346 ( 1996);
Jenekhe et al., Science, 279:1903-1907 ( 1998), which are hereby incorporated
by
reference). Because of the imprinted instructions for self organization with
well-defined
rod-coil interfaces, novel highly ordered 3-D aggregates, unlike conventional
surfactant
or block copolymer micelles, were formed (Figure 7). Examples of 3-D shaped
objects
that could be prepared by macromolecular self assembly are shown in Figure 27.
Compared to multiple morphologies (spherical, cylindrical, rings, and
lamellar) self assembled from diblock copolymers, triblock copolymers arranged
as only
one type morphology, i.e., spherical micelles under similar conditions, and
the size of
which was an order of magnitude larger than those of diblock copolymers.
Figure 20
shows the polarized optical micrographs and fluorescence micrographs of
triblock
copolymers (SSa, SSb, and SSc) prepared from TFA/DCM solutions with triblock
CA 02324140 2000-09-15
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copolymer concentration of 0.1 wt.%. All of the samples were prepared by
spreading the
solvents on hot glass substrates (90 °C). Only spherical micelles were
formed with sizes
ranging from 0.5 pm to 200 pm. For triblock copolymer PPQ;o-b-PS;oo-b-PPQ;o
(SSa),
perfect spherical micelles with sizes ranging from 20 - 40 p.m were observed.
However,
small spherical micelles with a size of 1 pm to ~ pm ( 10%) and very large
spherical
micelles with sizes ranging from 40 pm to 200 p.m were also observed ( 10%).
The
average size of spheres from copolymer PPQ;o-b-PS;oo-b-PPQ;o (SSa) was 27 pm.
Spherical aggregates self assembled from triblock copolymer PPQ;o-b-PS2;o-b-
PPQ;o
(SSb) had much narrower size distribution, with typical sizes in the range of
10 - 20 p.m
(90%), and the minor phase was very small spherical aggregates with sizes from
1 pm to
5 p.m ( 10%), giving an average size of 16 pm. Triblock copolymer PPQ;o-b-PS
i2o-b-
PPQ;o (SSc) also arranged as spherical aggregates in solid state, with sizes
ranging from
1 - ~ pm, with structures having severe defects with many holes developed in
the
micelles. The spherical aggregates from copolymers PPQ;o-b-PS;oo-b-PPQ;o and
PPQ;o-
b-PS~;o-b-PPQ;o (SSa and SSb) formed similar sizes arranged closed-packed in
substrates
in a hexagonal manner. All the spherical aggregates (with or without defects)
had highly
ordered structures, as indicated in images taken under cross polarizers
(Figures 20A, 20C,
and 20E).
The morphologies of the triblock copolymers prepared from different
processing temperatures (from 20 °C to 90 °C), copolymer
concentrations (0.01 - 0.5
wt%), and solvent ratios of TFA:DCM (from 9/1 to 1/9) were also investigated.
No
differences in size, shape, or hierarchical arrangement of spherical
aggregates was
observed for the various processing conditions, in sharp contrast to that of
diblock
copolymers, whose morphologies were highly dependent on the solvent ratio. For
the
samples prepared from solutions with very low copolymer concentrations (<
0.005 wt.%),
no spherical aggregates were observed under optical microscope, probably due
to the fact
that the size of the aggregates was too small to be detected by optical
microscopy. The
size of the spherical micelles was mainly determined by the length of the
coil. As DP of
PS decreased from 500 to 250, then to 120, the average diameter of spherical
micelles
correspondingly decreased from 27 p.m, to 16 pm, and then to 2 Vim, and no
correlation
could be found between the size and temperature or between size and solvent
ratio.
Although for each triblock, spherical aggregates had size distribution, the
aggregates with
similar sizes tended to stay together, and arranged in a hexagonal manner.
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The aggregation number for each aggregate was also estimated. For 55a,
0.5-g solution with copolymer concentration of 0.1 wt.% can cast a film with
area of 2
cm2. In this area. average density of the micelles with typical diameter of 30
Pm was
about 1.5 x 10~' /cm'. Therefore the aggregation number was calculated to be
3.3 x 10~°.
The aggregation number can also be estimated from density. Assuming the
micelle has
90 % porosity. the density of the micelles is close to 0.14 g/cm3. As the
volume for each
micelle is 1.4 x 10'~ pm3, aggregation number will be 1.5 x 10'°, very
close to that
estimated from the other method (see above). The aggregation number for 55b
(diameter
of 10 pm) and 55c {diameter of 2 pm) can be similarly estimated. The
aggregation
number was 5.6 x 1 O8, and 4.4 x l Ob, respectively.
Figure 28 shows the SEM micrographs of triblock copolymers 55a, 55b
and 55c prepared from TFA/DCM solutions with triblock copolymer concentrations
of
0.5 wt.%. All the samples were prepared by slowly evaporating the solvents at
room
temperature. For triblock copolymer PPQ;°-b-PS;oo-b-PPQ;o (55a)
(Figures 28A and
28B), perfect spherical aggregates with sizes ranging from 20 - 40 Pm were
observed,
however, large spherical micelles with sizes ranging from 40 p,m up to 200 um
were also
observed (20%). These large spherical aggregates (40 pm-200pm) had flattened
shapes
(Figures 28A and 28B). Samples from triblock copolymer PPQ;o-b-PSZSO-b-PPQ;o
(55b)
exhibited perfect spherical micelles with typical sizes in the range of 10 -
20 pm {Figure
28C). Triblock copolymer PPQ;°-b-PSi2o-b-PPQ;o (55c) also arranged as
spherical'
micelles in solid state; however, severe defects. such as holes with sizes
ranging from 0.5
p.m to 1 p.m, developed all through the structures (Figure 28D). Figures 28E
and 28F
show the SEM micrographs of broken spherical aggregates from copolymers 55a
and
55b, respectively. The microcavity inside the spherical micelles was clearly
revealed.
The wall thickness of the aggregate prepared from PPQ;o-b-PS;~-b-PPQ;o (55a)
varied
from 340 nm to 1100 nm, whereas the wall thickness varied from 250 nm to 540
nm for
copolymer PPQ;o-b-PS2;o-b-PPQ;o (55b). Because the extended lengths for
copolymer
55a and 55b were 180 nm and 120 nm, respectively, it appeared that the wall of
the
aggregates needed to be at least 2 to 6 extended copolymer molecules in order
to reach
the necessary thickness. Spherical aggregates from solutions with lower
copolymer
concentrations (0.1 wt.%, 0.05 wt.%, and 0.01 wt.%) were also prepared. SEM
studies of
these samples revealed that spherical aggregates in the range of 200 nm to
1000 nm were
also present, coexisting with the aggregates with sizes larger than 1 pm.
About ~-10 % of
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WO 99/47570 - 43 - PCT/US99/05940
the spheres whose sizes were in the range of 100 to 1000 nm were observed in
the sample
prepared from 0.1 and 0.5 wt.% solutions. In samples prepared from 0.01 wt.%
solution,
the numbers of the spherical aggregates with sizes in the range of 200 to 1000
nm
increased to almost 20 %. These results suggested that the concentration of
the solution
had significant effects on the size of the aggregates.
The spherical aggregates self assembled from triblock copolymers could
not be similarly explained as aggregates with inner-shell PS/outer-shell-PPQ
as diblock
copolymer could. The main difficulty was in the discrepancy of the wall
thickness. If the
triblock copolymer folds over and forms a loop-single layer, because the
lengths of the
triblock copolymers were all less than 180 nm, spherical aggregates with at
most 90-nm
thick walls would be expected. However, extensive studies revealed that the
wall
thickness varied from 250 nm to 1100 nm, indicating several layers were
present and
constituted the wall. Therefore. the spherical aggregates self assembled from
triblock
copolymers were vesicles which had one or several bilayer structures forming
the wall.
Although not wishing to be bound by theory, because no other morphologies
except
vesicles were obtained, a large portion of triblock copolymers may have folded
to form a
single layer, serving as the curvature-inducing factor to let bilayers form
vesicles instead
of lamellae (Szleifer et al., Proc. Natl. Acad. Sci. USA, 95:1032-1037 (1998);
Safran et
al., Science, 248:354-356 (1990); Dan et al., Euro~hys. Lett., 21:975 et seq.
(1993); Porte
et al., J. Chem. PhYs., 102:4290 et seq. (1993), which are hereby incorporated
by
reference). In fact, the aggregates formed by copolymer PPQ;o-b-PS,ZO-b-PPQ;o
(SSc)
suggested that bilayer structures were the central building units. The
spherical structure
with many holes developed within was a new structure called ''perforated
vesicles" or
sponge phase, arising from the need to avoid edges by making a continuous web
of
bilayer in a sponge-like structures (Hecht et al., Macromolecules, 28:5465-
5476 (1995);
Roux et al., J. Phys. Chem., 96:4174-4187 (1992); Hoffmann et ai., Lan muir,
8:2629-
2638 (1992), which are hereby incorporated by reference). "Perforated
vesicles" or
sponge phases have been reported in several systems (Safran et al., Science,
248:354-356
( 1990); Dan et al., Europhys. Lett., 21:975-980 ( 1993); Porte et al., J.
Chem. Phys.,
102:4290- (1993), which are hereby incorporated by reference). Because only
the
aggregates with sizes ranging from 1 - 15 ~m self assembled from copolymer
PPQ;o-b-
PS,2o-b-PPQ;o (SSc) into perforated vesicles, two factors, both large
curvature of the
CA 02324140 2000-09-15
WO 99/47570 - 44 - PCTNS99/05940
vesicles and the difficulty in folding to form single layers, might attribute
to the formation
of the sponge phase.
Transmission electron microscopy (TEM) technique was also used to
study the aggregates self assembled from diblock and triblock copolymers. The
samples
were prepared by dipping copper grids into 0.1 wt.% solutions at room
temperature, then
drying under a mild flow of air. Because large aggregates (> 1 pm) are too
heavy to hold
by the thin copolymer films formed between the grids, only small aggregates
could be
detected. Figure 29 shows typical TEM images from diblock copolymer PPQ,o-b-
PS3oo
(5417 (Figure 29A), PPQ;o-b-PS3oo (54c) (Figure 29B) and triblock copolymer
PPQ;o-b-
PS2;o-b-PPQ;o (55a) (Figure 29C) and PPQ;o-b-PS;oo-b-PPQ;o (55b) (Figure 29D).
i5 Spherical aggregates prepared from diblock PPQ,o-b-PS3oo (54f~ and PPQ;o-b-
PS3oo (54c)
in the range of 100 to 100 nm were clearly revealed in Figures 29A and 29B,
whereas
spherical aggregates with sizes varying from 150 nm to 800 nm were shown in
Figures
29C and 29D. Based on this information, it seemed that the molecular packing
in diblock
and triblock copolymer was different, as evidenced from Figure 29A and Figure
29D.
The spherical aggregates from triblock copolymers were more structured; a
concentric
ring-like image was revealed in TEM. It also seemed that folding did occur in
triblock
copolymers. The smallest size of the vesicles shown in Figures 29C and 29D was
about
150 nm. Because the fully extended length for triblock PPQ;o-b-PS;oo-b-PPQ;o
(55a) and
PPQ;o-b-PS2;o-b-PPQ;o (55b) was about 180 nm and 120 nm, respectively, the
results
suggested that the folded loop-single layer (Figure 14) was the main building
unit for the
vesicles (< 600 nm).
Example 4 - Some Characterization Results
The synthetic approaches outlined in Figures 5 and 6 ensured that the
desired rod-coil block copolymer structures (54a-54g and 55a-55c) were
obtained. The
composition of the diblocks ANABNA and triblocks ANABNBANA Was COntrOlled by
the
stoichiometric method, where A and B were the PPQ and PS repeat units,
respectively.
Various techniques, including solvent extraction, ~H NMR and FTIR
spectroscopies,
DSC, and TGA were used to confirm the proposed structures and compositions. To
establish that the copolymer samples were rod-coil block copolymers and not
physical
blends, Soxhlet extraction using refluxing ethyl acetate, which is a selective
solvent for
the coil-like block (PS), was performed on PPQ;o-b-PS~3o (54d) and PPQ;o-b-
PS~ZO-b-
CA 02324140 2000-09-15
WO 99/47570 - 45 - PCTNS99105940
PPQ;o (SSc). The yields were higher than 95% after 24 hours extraction,
whereas
continued extraction past this time resulted in no additional weight loss,
indicating that all
the flexible coil blocks in the sample were chemically bonded to the rigid-rod
PPQ.
TGA thermograms of the rod-coil block samples are shown in Figures 30
and 31. TGA thermograms of the PPQ and PS homopolymers were also obtained for
comparison. The decomposition temperatures of PPQ and PS were 600 °C
and
400 °C, respectively. TGA thermograms of the block copolymers showed a
two-step
decomposition in flowing N2. The onset of the first thermal decomposition of
the rod-coil
blocks was 420 °C for 54c and 54d, 400 °C for 54a, 54b, 54e-54g,
and 4l 0 °C for SSa-
SSc, which was assigned to the decomposition of the flexible-coil PS block.
(Figures 31A
and 31 B). The slightly improved thermal stability of the PS block in the rod-
coil block
copolymers compared to the parent PS homopolymer can be understood as a
consequence
of the tethering of the former chains onto rigid-rod chains. After the
decomposition of the
flexible-coil blocks, the PPQ blocks were stable until 600 °C, which
was identical to the
decomposition temperature of the PPQ homopolymer. Observation of two
characteristic
decomposition temperatures indicated that the samples were block copolymers
and not
random copolymers. The weight losses of block copolymers in the 400 to 600
°C ranges
are shown in Tables 3 and 4, below.
CA 02324140 2000-09-15
WO 99/47570 _ 46 _ PCT/US99/05940
0
0 0 _
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CA 02324140 2000-09-15
WO 99/47570 _ 4~ _ PCT/US99/05940
U
0
o cv'a o~ ~ ~ ~ ~ o'~o
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'E ~ p C% V1 C% (n Cn Cn
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U
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O
L
E c0O .aO U O p O N~ 4-.O O
p p O ~'~ O O p~
a> >, ~'N V ~ 'fit' C'~ C'.-.~t~ r1
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d ~n ~, O
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to
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CA 02324140 2000-09-15
WO 99/47570 - 4g - PCT/US99/05940
The measured weight losses in the 400 to 600 °C ranges and hence
estimated NA, were in
excellent agreement with the calculated composition of block copolymers. The 4
difference between the expected block copolymer composition in PPQ;o-b-PS2;o-b-
PPQ;o
(55b) and that estimated from TGA data can be accounted for by the residual
weight of
the PS block in the 400 to 600 °C range and was well within the
experimental accuracy of
TGA analysis for composition determination.
The DSC thermograms of the rod-coil block copolymers, and those of the
two parent homopolymers were also obtained. PS homopolymer had a glass
transition
temperature (Ta) at 100 °C. No crystalline melting or TQ was observed
in PPQ before
reaching its decomposition, consistent with the excellent thermal stability
and high
modulus of rigid rod-like conjugated polyquinolines. The DSC thermograms of
the
diblock copolymers 54a-54g were essentially superpositions of those of the two
parent
homopolymers, exhibiting only a glass transition at 100 °C. However,
the DSC
thermograms of triblock copolymers 55a-c behaved quite differently. The DSC
thermograms of PPQ;o-b-PS;~-b-PPQ;o (55a) and PPQ;o-b-PS2;o-b-PPQ;o (55b) in
the
first scan showed a second-order transition with temperature at 114 °C,
and subsequent
scans of the samples were identical to those of the initial scans. The DSC
thermogram of
PPQ;o-b-PS~2o-b-PPQso (55c) showed a straight line from -50 to 400 °C;
no discernible
transition was observed. Compared to polystyrene homopolymer, triblock
copolymers
PPQ;o-b-PS;~-b-PPQ;o (55a) and PPQ;o-b-PS2;o-b-PPQ;o (55b) exhibited an
enhanced
glass transition temperature by 14 degrees. Copolymer PPQ;o-b-PSi2o-b-PPQ;o
(55c),
which had the shortest coil block length (Dp ~ 120), exhibited no glass
transition at all in
the temperature range of -50 to 400 °C, indicating its glass transition
temperature was
higher than 400 °C. These results suggested that the tethering of both
ends of the flexible
PS chains to rigid-rod blocks had tremendous effects on the glass transition
of the PS; the
movement of the PS was severely limited by the anchors on the ends. As the
enhancement of T~ in conventional coil-coil triblock copolymers was not
observed, nor in
PPQ-PS diblock copolymers, which had numbers of PS repeat units (DP) ranging
from
2000 to 130, close to the DP of PS in triblock copolymers (500 to 120), two
factors, both
the tethering of the PS on both ends and the rigid rod-like nature of the
blocks PS was
tethered to, are believed to have contributed to the enhancement of the glass
transition
temperature.
~H NMR spectra of 54a-54g and 55a-55c in deuterated nitrobenzene
containing AIC 13 were obtained and assigned to the proposed structures by
comparison
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WO 99/47570 - 49 - PCT/US99/05940
with those of the PPQ and PS homopolymers. 1 H NMR spectra of copolymers were
essentially superpositions of those of two parent components, PPQ and PS.
Figure 32
shows a typical IH NMR spectrum of copolymer PPQ;o-b-PS;~-PPQ;o (55a). The
protons of the PPQ block appeared as resonances at 9.7, 9.4-9.6, 9.2 and 8.9
ppm, which
were assigned to the protons of the quinoline ring. Protons of the side group
phenyl ring
appeared at 7.5 ppm, overlapping with the signals from the nitrobenzene
solvent. Protons
of the PS block had resonances at 7.3-7.4 and 6.7-6.8 ppm, assigned to the
phenyl ring,
and at 1.5-I .6 and 2.2 ppm due to resonances of the protons of the methylene
units.
Comparison of the integral of PPQ proton resonances in the range 8.8-9.8 ppm
to that of
the methylene units in the range of 1.5-2.2 ppm, gave the average repeat units
of PPQ in
54a-54d as around 50, 54e-54g as around 10, and 55a-55c as around 100,
respectively.
These results were in good agreement with the proposed block copolymer
composition.
FTIR spectra were also obtained as an independent check for the
molecular structure of the rod-coil block copolymers. (Figure 33) The FTIR
spectra of
the rod-coil block copolymer samples were essentially superpositions of the
spectra of the
parent PS and PPQ homopolymers. There were significant differences between the
vibrational spectra of PS and PPQ homopolymers and hence their contributions
to the
FTIR spectra of the block copolymers 54a-g and 55a-c. For example, the
vibrational
bands at 2922 and 2949 cm-~, which can be assigned to aliphatic C-H stretching
in PS,
were absent in the FTIR spectrum of PPQ homopolymer. On the other hand. the
strong
bands at 1346 and 1028 cm ~ were characteristic of the quinoline ring of the
PPQ block.
The FTIR results in conjunction with the ~H NMR spectra, DSC and TGA
thermograms,
and other characterizations of the rod-coil block copolymer samples confirmed
their
proposed structures and compositions.
For all the diblock and triblock copolymers, it seemed that aggregates were
spontaneously formed in solutions with concentration of 0.01 to 0.5 wt.%. No
size
difference was observed for various copolymer concentrations, although for
lower
concentration. the density of the aggregates was much less. For very dilute
solutions with
concentrations equal to or below 0.001 wt.%. no discernible aggregates were
observed,
suggesting that concentration of 1x10-~ M probably was the critical
concentration for
forming aggregates with size larger than 1 p.m. Spherical aggregates prepared
from
diblock copolymer PPQ;o-b-PS~o~ (54b) with size in the range of 1 to 20 um
(Figure
21 A), and cylindrical aggregates from diblock copolymer PPQ;o-b-PS3~ (54c)
with
CA 02324140 2000-09-15
WO 99/47570 - 50 - PCTNS99105940
~ diameter of 1 pm and length of 1 to 20 p.m (Figure 21 B), were observed.
Under cross-
polarizers, no structures could be revealed probably due to the fact that the
wall of the
structure was too thin. Vesicles formed from triblock copolymer PPQ;o-b-PS;oo-
b-PPQ;o
(55a) had size ranges of 5 Pm to 120 p.m (Figures 21 C, 21 D, and 21 E),
whereas vesicles
from copolymer PPQ;o-b-PS2;o-b-PPQ;o (55b) (Figure 21F) and PPQ;o-b-PS,2o-b-
PPQ;o
(55c) had sizes in the range of 1 to 100 pm, and I to 15 um, respectively. The
vesicles
from triblock copolymers PPQ;o-b-PS;oo-b-PPQ;o (55a) and PPQ;o-b-PSZ;o-b-PPQ;o
{55b) were perfect; no flat or elongated shapes were observed. However,
vesicles from
copolymer PPQ;o-b-PSi2o-b-PPQ;o (55c) had severe deformities in the
structures, with
holes developed all through the structures. All the vesicles (with or without
defects)
seemed to have highly ordered structures, as evidenced by the images taken
under cross
polarizers (Figure 21 C). All these results were consistent with the
observation from the
samples in solid state. The only exception was that no vesicle with a
flattened shape was
observed for triblock copolymer PPQ;o-b-PS;oo-b-PPQ;o (55a) in solutions. as
evidenced
by the studies when the tubes were rotated. This indicated that the vesicles
with a
flattened shape (Figures 28A and 28B) were caused by inadequate mechanical
strength of
the spherical structures.
The aggregates in solutions were colloidal stable; they remained intact and
had no tendency to precipitate or coagulate after standing for several weeks
at 20 °C. The
spherical aggregates from diblock copolymers had similar optical transparency,
suggesting they had the same wall thickness. In contrast, vesicles prepared
from triblock
copolymers had at least three types of wall-thickness: thin-wall, medium-wall,
and thick-
wall (Figures 21 C-21 F). These vesicles with different wall-thickness
appeared in all the
sizes and the vesicles with the thinnest wall had the same optical
transparency as the
aggregates self assembled from diblock copolymers (Figure 21A). If the
solutions were
perturbed, the vesicles began to move against each other and no attraction or
repulsion
was observed between two aggregates when they moved closer. When two
aggregates
were in contact range no merging of the aggregates or deforming of one or two
aggregates were observed.
The driving force for the large size and hollow cavity of aggregates
appeared to be a more efficient packing of the rigid-rod blocks and.
consequently, a more
ordered and stable aggregate structure. All the different aggregates under
cross-polarizers
showed that they were highly ordered with crystalline features. The different
building
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WO 99/47570 - 51 - PCT/US99/05940
units for the spherical aggregates from diblock and from triblock copolymers
led to the
many differences between the aggregates from diblock and triblock copolymers.
Such
differences included the fact that the size of the latter was about an order
of magnitude
larger and the presence of multiple wall thicknesses of the aggregates from
the triblock
copolymers.
Example 5 - Solubilization Studies
Materials
The two copolymer compositions of poly(phenylquinoline)-block-
polystyrene used in this study, denoted here as PPQ;o-b-PS3oo (54c) and PPQ,o-
b-PS3oo
(54fj, were synthesized by coupling functionalized polystyrene (PS) with the
PPQ
monomer. 5-acetyl-2-aminobenzophenone (Sybert et al., Macromolecules, 14:493-
502
( 1981 ). which is hereby incorporated by reference), followed by
polycondensation
synthesis of the PPQ block. The starting monofunctionalized PS had a reported
number
average degree of polymerization of 300 and a polydispersity of 1.05 (Aldrich,
Milwaukee, WI). The number average degree of polymerization of the PPQ blocks
was
determined from ' H NMR spectra, thermal analysis, and other data.
Analytical grade solvents trifluoroacetic acid (TFA), dichloromethane
(DCM), carbon disulfide (CS2), and toluene were purchased from Aldrich
(Milwaukee,
WI) and were used as received. Fullerene molecules C6o (TCI, 99.9 %) and Coo
(Aldrich,
Milwaukee, WI 99 %) were used as received. Polyethylene oxide) (PEO) (M,~ of
5,000,000, MW/M" ~2.8), poly(methyl methacrylate) (MW of 350,000, M,y/M~ 1.15)
and
polystyrene (M,~ of 6,000,000, MW/M° ~1.2) were purchased from
Polysciences, Inc.
(Warrington, PA) and were used as received.
Micellization and Solubilization Procedures
Copolymer solutions of PPQ-b-PS block copolymers (PPQ;o-b-PS3oo (54c)
and PPQ,o-b-PS3oo (54f)) (0.5 to 1 mg/ml) used for the solubilization studies
were
prepared by dissolving each copolymer in various TFA/DCM or TFA/toluene
mixtures of
9/1, 7/1, 1/1, and 1/4 solvent volume ratios. The resulting solutions had
concentrations of
0.35 to 3.5 mg/ml (0.05 to 0.5 wt.%) of diblock copolymers. The critical
micelle
concentration (cmc) of PPQ-PS block copolymers in these binary solvents was
unknown,
but much less than order 10-3 wt.%. A known amount of fullerene (C6o or Coo,)
was then
CA 02324140 2000-09-15
WO 99/47570 - 52 - PCT/US99/05940
added to the pre-made copolymer solutions. Alternatively, fullerene/copolymer
solutions
were prepared by adding know amounts of solid polymer and fullerene to the
binary
TFA/DCM or TFA/toluene at the same time to achieve solutions with similar
concentrations. Fullerene/copolymer solutions were also prepared by mixing a
solution
of fullerene in DCM or in toluene with a pre-made copolymer solution.
Different weight
ratios of fullerene to copolymer were employed, ranging from 0.1 to 50 wt.%.
The
fullerene/copolymer solutions were then stored for at least 2 days to
equilibrate before
assessment of solubilization and preparation of fullerene/block copolymer
aggregates.
Films (~1 to 20 p.m thick) resulting from drying the dilute solutions of
block copolymer/solubilized fullerenes on glass slides at room temperature
were
investigated as made. or after treating them in 5 % triethylamine/ethanol (to
remove any
trace acids). and drying in a vacuum oven at 60 °C for 24 hours. The
films were
investigated by polarized optical and fluorescence microscopies as well as by
UV-Vis
absorption and photoluminescence spectroscopies.
Preliminary experiments on the release of encapsulated fullerenes were
done by placing dried fullerene/copolymer aggregates in either good solvents
for the
rigid-rod PPQ block (fresh, clear, 1:1 TFA:DCM or TFAaoluene solvent mixtures)
or
good solvents for the coil-like PS block (pure DCM or toluene). Release of
encapsulated
fullerene was monitored by optical absorption spectroscopy to track any
absorption
signals of fullerene in solution.
Absorption spectra of solutions (0.1 wt.%) of fullerene C6o and Coo in CSC
were obtained using a quartz cuvet which was sealed by wax to prevent solvent
evaporation. Absorption spectra of the pure PPQ;o-b-PS3oo (54c) and PPQ,o-b-
PS3oo (~4fj
were similarly obtained in 1:1 TFA:DCM solutions at 0.1 wt.% which was orders
of
magnitude larger than their cmc. These were used as the reference spectra for
comparing
the absorption spectra of solubilized fullerene/block copolymer micelles. The
UV-Vis
absorption spectra of all fullerene/PPQ-PS dispersions were obtained in a 1-mm
cuvet at
room temperature (25 °C) and were used to estimate the solubilization
capacities of the
fullerene/PPQ-PS systems. For this purpose, the absorbance of each UV-Vis
spectrum
was normalized at a characteristic C6o or Coo absorption band. The normalized
absorbance was then plotted as a function of the amount of fullerene added to
a
dispersion. The saturation of the normalized absorbance versus fullerene
loading
provided an estimate of the maximum amount that was solubilized.
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The normalized absorbance X of solutions of C6o/diblock copolymers at
330 nm was given by X= C~NA~ ~A330'A°330~/~ A422-A°422J, where X
is proportional to C6o
solubilized per diblock copolymer chain in solution, C is a constant, which is
the ratio of
the absorption coefficients of the PPQ block at 422 nm and C6o at 330 nm, NA
is the
number of repeat units of PPQ in the diblock copolymer. and A33o and A422 are
the
I 0 absorbances at 330 and 422 nm, respectively. A°33o is the
calculated absorbance of PPQ
at 330 nm whereas A°42z is the calculated absorbance of C6o at 422 nm.
Because of the
negligible absorbance of Cbo at 422 nm, A°422 = 0. For solutions of
C~o/diblock
copolymers, the normalized absorbance was Y= C~NA~ (A4~3-A°4~3]I~ A33s-
A°33s], where
Y is proportional to Coo solubilized per diblock copolymer chain, C is a
constant, which is
15 the ratio of the absorption coefficients of PPQ at 335 nm and C6o at 473
nm, NA is the
number of repeat units of PPQ in the diblock copolymer, and A33; and A4~3 are
the
absorbances at 335 and 473 nm. respectively. A°33s is the calculated
absorbance of Cbo at
335 nm whereas A°4~3 is the calculated absorbance of PPQ at 473 nm.
Because of the
negligible absorbance of PPQ at 473 nm, A°4~3 = 0.
20 Films of solid aggregates were too scattering in the visible region to
obtain
normal optical absorption spectra. Dilute solution optical absorption spectra
of the pure
fullerene and fullerene/copolymer samples, and those of thin films of block
copolymers
dispersed {0. I wt%) in polyethylene oxide) (PEO) were recorded on a Perkin-
Elmer
Model Lambda 9 UV/VIS/NIR Spectrophotometer. All spectra were obtained at room
25 temperature (25 °C).
Samples for observation by polarized optical microscopy (POM) and
fluorescence microscopy (FM) were prepared by allowing several drops of a
fullerene/block copolymer solution in TFA:DCM or TFAaoluene to spread and dry
on
glass slides. The various drying conditions explored were described above and
were
30 found not to influence the observed morphologies of aggregates (size,
shape, and their
distributions). Observations were made on an Olympus Model BX60 Fluorescence
Optical Microscope and optical (bright field, polarized light) and
fluorescence images
were recorded by a digital camera.
Photoluminescence (PL) and photoluminescence excitation (PLE) spectra
35 were obtained on a Spex Fluorolog-2 spectrofluorimeter. Thin films of
aggregates were
measured by using the front face geometry in which samples were positioned
such that
the emission was detected at 22.5° from the incident radiation beam.
Further details of
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the photophysical experimental techniques used here are similar to those we
have
described in detail elsewhere (Osaheni et al., J. Am. Chem. Soc., 117:7389-
7398 ( 1995);
Jenekhe et al., Science, 265:765-768 ( 1994), which are hereby incorporated by
reference).
The DSC thermograms were obtained on a Du Pont Model 2100 Thermal
Analyst based on an IBM PS/2 Model 60 computer and equipped with a Model 910
DSC
unit. The DSC thermograms of samples were obtained in nitrogen at a heating
rate of
10 °C/min. Samples for DSC measurements were prepared by casting films
of
fullerene/PPQ;o-b-PS3oo (54c) solutions in TFA/DCM (1/1, v/v) onto glass
slides and
carefully removing vacuum dried fullerene-containing aggregates from glass
slides into
DSC sample pans by using a sharp razor blade. Before the aggregates were
removed
from the glass slides, they were observed by an optical microscope to
ascertain their
spherical micellar morphology. In the case of fullerene/polystyrene and
fullerene/poiy(methyl methacrylate) samples. drops of solutions in CS2 were
dried
directly in aluminum DSC pans.
Micellar Solubilization ofFullerenes.
PPQ-PS solutions in the two binary solvent systems TFA/DCM and
TFA/toluene were previously shown to undergo self organization to produce
hollow
spheres, tubules and other aggregates (See Examples 3-4; Jenekhe et al.,
Science.
279:1903-1907 (1998), which is hereby incorporated by reference). Both solvent
systems
were selective for the PPQ block and were highly polar. Both C6o and Coo were
insoluble
in pure TFA or TFA/DCM or TFA/toluene mixtures (4/1 to 1/4, v/v) even though
the
fullerenes were slightly soluble in pure DCM (0.192 mg/g) and pure toluene
(3.16 mg/g ).
Both C6o and Coo readily dissolved in these binary solvents at room
temperature (25 °C)
when either PPQ;o-b-PS3oo (54c) or PPQ,o-b-PS3oo (54fj was present as
illustrated in
Figure 34. Optical absorption experiments on the resulting solutions showed
strong
characteristic fullerene absorption bands (Dresselhaus et al., Science of
Fullerenes and
Carbon Nanotubes, Academic Press, San Diego, California (1996); Hirsch et al.,
The
Chemistry of the Fullerenes, Georg Thieme Verlag, Stuttgart (1994), which are
hereby
incorporated by reference), indicating the presence of fullerene in solution
and hence
evidence of enhanced solubility facilitated by the amphiphilic block
copolymers.
Figure 35 shows the absorption spectra of TFA/DCM solutions of pure
PPQ;o-b-PS3oo (54c) (Figure 36A), PPQ;o-b-PS3oo (S4c) with 5 wt % Cbo (Figure
35B),
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WO 99/47570 - 55 - PCT/US99/05940
together with the spectrum of pure Cbo in CS2 (Figure 35C). The spectrum of
C6o/PPQso-
b-PS3oo blend solution showed absorption bands characteristic of the two
components, C~
and the diblock copolymer PPQso-b-PS3oo (54c). The absorption band in the 370-
460 nm
region with maxima at 405 nm was due to the PPQ block of the copolymer. The
sharp
peak at 330 nm was due to the optical transition of C6o. The magnified version
of the
blend spectrum in the 400-700 nm region is shown as the insert of Figure 35.
The
absorption bands with .mar at 540 and 600 nm were characteristic absorption
bands of
C6o. Figure 36 shows the absorption spectra of 5 wt.% C~dPPQ;o-b-PS3~ and S.wt
CyPPQ~o-b-PS3oo in TFA/DCM and Coo in CS2. The characteristic Coo absorptions
at
335, 383 and 473 nm and PPQ-PS absorption centered at 405 nm were observed in
the
C~o/PPQ-PS solution spectra which could be readily deconvoluted into the
component
spectra. The fact that the absorption spectra of the Cbo/PPQ;o-b-PS3oo and
C~o/PPQ$o-b-
PS3oo solutions were a superposition of the two chromophoric components
(fullerene and
pure diblock copolymer) suggested that there was no ground state electronic
interaction
between the fullerenes and the conjugated PPQ segments. This was to be
expected since
the fullerenes C6o and Coo were strong electron accepting molecules
(Dresselhaus et al.,
Science of Fullerenes and Carbon Nanotubes, Academic Press, San Diego,
California
( 1996); Hirsch et al., The Chemistry of the Fullerenes, Georg Thieme Verlag,
Stuttgart
( 1994); Adreoni, ed., The Chemical Physics of Fullerenes 10 (and 5) Years
Later, Kluwer
Academic Publishers, Dordrecht, The Netherlands (1996); Hebard et al., Nature,
350:600-
601 ( 1991 ); Zakhidov et ai., Phvs. Lett., 205:317-326 ( 1995); Kaj ii et
al., Synth. Met.,
86:2351-2352 (1997); Sariciftci et al., Science, 258:1474-1476 (1992);
Sariciftci et al.,
Appl. Phys. Lett., 62:585-587 (1993); Wang, Nature, 356:585-587 (1992); and
Wang et
al., J. Phys. Chem., 1 O 1:5627-5638 ( 1997), which are hereby incorporated by
reference)
as are the conjugated polyquinolines (Sybert et al., Macromolecules, 14:493-
502 ( 1981 );
Agrawal et al., Macromolecules, 26:895-905 (1993); Agrawal et al., Chem.
Mater.,
8:579-589 (1996); Agrawal et al., J. Phys. Chem., 96:2837 et seq. (1992);
Jenekhe et al.,
Chem. Mater., 9:409 et seq. ( 1997), which are hereby incorporated by
reference).
Therefore, absorption spectroscopy could be used to quantify the
solubilization capacity
of fullerenes in the block copolymer solutions.
All solubilization studies and solution optical absorption measurements
were done on the four basic systems: C6o/PPQso-b-PS3oo~ Cbo/PPQio-b-PS3oo,
C~o/PPQso-b-
PS3oo, and C~o/PPQ,o-b-Ps3oo. In addition to the two different approaches to
preparing
CA 02324140 2000-09-15
WO 99/47570 - 56 - PCT/US99/05940
solubilized fullerene/block copolymer solutions illustrated in Figure 34,
i.e., addition of
solid fullerene to a pre-existing copolymer solution and addition of both
fullerene and
block copolymer to the solvent mixture. fullerene/PPQ-PS solutions were also
prepared
by mixing a solution of fullerene in DCM with a pre-made copolymer solution.
No
discernible differences were observed between the three methods. Similar
solution
absorption spectra and, subsequently, similar aggregate morphologies were
obtained.
This suggested that the observed solubilization behavior was likely near
equilibrium
conditions.
Normalized absorbancies of the characteristic fullerene absorption bands
were used as measures of the relative amounts of fullerene solubilized in the
block
copolymer solutions. Figure 37A shows plots of normalized Cbo absorbance at
330 nm
versus Cbo loading into the solution (mg C6o per g diblock copolymer in
solution). The
relative amount of solubilized Cbo increased linearly with the fullerene
loading of the
diblock copolymer solutions, reaching saturation at a loading of about 200
mg/g. This
was taken as the solubiIization capacity of the block copolymer solutions. The
C6o
solubilization characteristics of PPQ;o-b-PS3oo (54c) and PPQ~o-b-PS3oo (54f]
were
essentially identical as were the different copolymer concentrations (Figure
37A).
Similar data of normalized absorbance versus loading for Coo are shown in
Figure 37B. A
solubilization capacity of 200 mg fullerene -C~o/g diblock copolymer was
obtained.
This was identical to the Cbo result. The solubilization capacity of 200 mg/g
translated to
11.8 and 9.2 solubilized Cbo molecules per diblock chain for PPQ;o-b-PS3o
(54c) and
PPQio-b-PS3oo (54f7, respectively. Similarly, the maximum amount of
solubilized Coo
molecule per diblock chain of PPQ;o-b-PS3oo and PPQ,o-b-PS3oo were 10.1 and
7.9,
respectively.
The measured solubiIization capacity of 200 mg of solubilized fullerene
(C6o or Coo) per gram of diblock copolymer represented a solubility
enhancement by
factors of 1040 and 63 compared to the solubilities in pure dichloromethane
and toluene,
respectively. The best previously reported, organic solvent for C6o was 1-
chloronaphthalene which had a solubility limit of 42.7 mg/g at room
temperature (22 °C)
(Dresselhaus et al., Science of Fullerenes and Carbon Nanotubes, Academic
Press, San
Diego, California (1996); Ruoff et al., J. Phys. Chem., 97:3379 et seg.
(1993); Sivaraman
et al., J. Org. Chem., 57:6077 et seq. (1992), which are hereby incorporated
by reference).
The large enhancement of fullerene solubility in organic solvents by
amphiphilic block
CA 02324140 2000-09-15
WO 99/47570 PCT/tIS99/05940
- 57 -
copolymer micelles that was demonstrated is thus very promising for potential
applications in the large scale extraction, purification, and processing of
fullerenes
(Dresselhaus et al., Science of Fullerenes and Carbon Nanotubes, Academic
Press. San
Diego, California ( 1996); Hirsch. The Chemistry of the Fullerenes, Georg
Thieme Verlag,
Stuttgart ( I 994), which are hereby incorporated by reference).
In preliminary experiments on the release of encapsulated fullerenes, PPQ-
PS micellar aggregates containing 1 and 5 wt.% fullerenes C6o and Coo from
TFA/DCM
and TFA/toluene solutions were dried and then placed in pure DCM or toluene,
which are
good solvents for PS block, for several days. Release of any encapsulated
fullerene was
not observed by optical absorption spectroscopy which did not detect any
absorption
I S signals of fullerene in solution. Subsequent examination of these
aggregates by optical
microscopy showed that there was no change in the morphology, before and after
their
immersion in the aprotic organic solvents. However, when similarly dried
aggregates
were immersed in TFA/DCM or TFA/toluene solvent mixture (1/1, v/v), they
dissolved
and progressively released fullerene into solution as judged by absorption
spectroscopy
which revealed and could be used to track the fullerene absorption signal in
solution. The
preliminary indication is that the release could be triggered and controlled
by pH.
Given the novel hollow structure and very large sizes of PPQ-PS micelles
and some of the unusual features of their solubiIization of fullerenes, it was
not obvious
that current theories of block copolymer micellization and solubilization
could explain the
experimental results (Nagarajan et al., Macromolecules, 22:4312 et seg.
(1989);
Nagarajan et al., J. Chem. Phvs., 90:5843 et seq. (1989); Hurter et al.,
Macromolecules,
26:5030 et seq. (1993); Hurter et al., Macromolecules, 26:5592 et seq. (1993);
Linse,
Macromolecules, 27:2685 et seq. (1994); Cogan et al., LanQmuir, 8:429 et seq.
(1992);
and Xing et al., Macromolecules, 30:1711 et seq. { 1997), which are hereby
incorporated
by reference). One basic issue was whether the observed solubilization of
fullerenes by
PPQ-PS diblock copolymer assemblies was a micellar solubilization phenomenon
(Solvents and Self Organization of Polymers, Webber et al., Eds., Kluwer
Academic
Publishers, Dordrecht, The Netherlands ( 1996), which is hereby incorporated
by
reference) or vesicle-like trapping (Vesicles, Rosoff, Ed., Marcel Dekker, New
York
( 1996), which is hereby incorporated by reference), or a hybrid of both.
Arguing in favor
of a micellar mechanism included the similarity of the solubilization capacity
regardless
of the self assembly path (Figure 34) which implied that the solubilized
fullerene/PPQ-PS
assemblies were thermodynamically very stable structures; as will be shown
below,
CA 02324140 2000-09-15
WO 99/47570 - 58 - PCT/US99/05940
fullerene solubilization caused major changes in the physical size,
aggregation number,
shape, and molecular packing of PPQ-PS aggregates. On the other hand,
independence of
solubilization capacity from copolymer concentration in solution and from the
PPQ block
length (NA~10 and 50 ) was not a common feature of block copolymer micelle
solubilization (Nagarajan et al., Macromolecules, 22:4312 et seg. (1989);
Nagarajan et al.,
J. Chem. Ph ~Ls., 90:5843 et seg. ( 1989); Hurter et al., Macromolecules.
26:5030 et seq.
(1993); Hurter et al., Macromolecules, 26:5592 et seq. (1993); Linse,
Macromolecules,
27:2685 et seq. (1994); Cogan et~al., Lan; muir, 8:429 et seq. (1992); and
Xing et aL,
Macromolecules, 30:1711 et seg. ( 1997), which are hereby incorporated by
reference) but
may reflect the hollow cavity of these assemblies. Nevertheless, some aspects
of the
results could be rationalized in terms of micellar solubilization theory for
block
copolymers (Nagarajan et al., Macromolecules, 22:4312 et seq. (1989);
Nagarajan et al.,
J. Chem. Phys., 90:5843 et seq. ( 1989); Hurter et al., Macromolecules,
26:5030 et seq.
(1993); Hurter et al., Macromolecules, 26:5592 et seq. (1993); Linse,
Macromolecules,
27:2685 et seq. { 1994); Cogan et al., Lan~muir, 8:429 et seq. ( 1992); and
Xing et al.,
Macromolecules, 30:1711 et seq. ( 1997), which are hereby incorporated by
reference).
From the known solubility parameters of fullerene-C6o (8~) (Dresselhaus et
al., Science of
Fullerenes and Carbon Nanotubes, Academic Press, San Diego, CA ( 1996). which
is
hereby incorporated by reference) and polystyrene (8P5) (Po~mer Handbook,
Brandrup et
al.. Eds., 3'd ed., Wiley, New York Chapter V, pp. 77-86 (1989), which is
hereby
incorporated by reference) which were 10 and 8.7 to 9.9 at 25 °C,
respectively. the Flory-
Huggins interaction parameter xr PS expressed in terms of the solubility
parameters
(Nagarajan et al., Macromolecules, 22:4312 et seq. (1989); Nagarajan et al.,
J. Chem.
Phys., 90:5843 et seq. ( 1989), which are hereby incorporated by reference)
xr. P5 = (8t~
8PS)2v~/ksT was as small as 0.015, where of is molar volume, kB is the
Boltzmann's
constant, and T= 298K. This suggested that there was strong interaction
between the
fullerene and the PS blocks. Prior investigations of C6o solubility in many
organic
solvents had shown that the largest solubilities were observed in solvents
with solubility
parameters close to that of C6o (Dresselhaus et al., Science of Fullerenes and
Carbon
Nanotubes, Academic Press, San Diego, CA ( 1996); Ruoff et al., J. Phys.
Chem., 97:3379
et seq. (1993); Sivaraman et al., J. Ors. Chem., 57:6077 et seq. (1992), which
are hereby
incorporated by reference).
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Block Copolymer Aggregates with Encapsulated Fullerenes.
The morphology of fullerene-containing block copolymer aggregates
which were dried from solutions was extensively investigated. Unlike the
multiple
aggregate morphologies (hollow spheres, tubules. lamellae. and doughnuts)
observed in
the pure PPQ;o-b-PS3oo (54c) and PPQ,o-b-PS3oo (S4~ diblock copolymers (See
Examples
3-4; Jenekhe et al., Science, 279:1903-1907 ( 1998), which is hereby
incorporated by
reference), solid films from all fullerene-containing copolymer solutions with
fullerene/copolymer ratios of 0.1 to 6 wt % showed only spherical aggregates.
Films cast
from solutions with fullerene concentration below this range were similar to
the pure
diblock copolymer solutions in exhibiting multiple aggregate morphologies.
This meant
1 S that the solubilized fullerenes at this dilute loading were encapsulated
in some of the
aggregates without influencing the block copolymer self organization process
in solution.
At fullerene loading of 7 wt.% or higher, the solid films showed mixed
morphologies
consisting of spherical aggregates with encapsulated fullerene as well as
needle-like
crystals of the pure C6o or Coo.
Figures 38-40 show the typical morphologies of PPQ;o-b-PS3oo (54c)
aggregates with encapsulated fullerenes revealed by optical and fluorescence
microscopies. Figure 38 shows the fluorescence (Figure 38A-B) and polarized
optical
(Figure 38C) micrographs of a 0.1 wt.% C~o/PPQ;o-b-PS3oo copolymer sample.
Only
spherical aggregates, with a typical diameter of about 10 p,m, were observed.
The
spherical aggregates had highly ordered structures as indicated by the
polarized optical
micrographs such as that shown in Figure 38C. Compared to the typical
spherical
aggregates of pure PPQ;o-b-PS3ob (54c) which were about 5 pm in diameter, an
enlargement of about a factor of 2 resulted from Coo encapsulation, even at
this low
loading level. Also, these aggregates with encapsulated Coo were not very
perfect
spheres, having many rough surfaces and edges. In contrast, the empty hollow
spheres
from all the diblock copolymers had perfectly round geometry and very smooth
surfaces
when compared on the same size scale. Figure 38D shows a typical morphology of
fullerene-Cbo encapsulated in PPQ;o-b-PS3oo (54c) at 0.1 wt.% loading. The
spherical
aggregates were very similar in size, shape and size uniformity to the PPQ;o-b-
PS3oo (54c)
aggregates containing 0.1 wt.% Coo.
Figures 39 and 40 show the photomicrographs of 1 % Cbo/PPQ;o-b-PS3oo
and 6% C6o/PPQ;o-b-PS3oo samples, respectively. The average diameter of the
aggregates
CA 02324140 2000-09-15
WO 99/47570 - 60 - PCT/US99/05940
in Figure 39 was 20 pm. Fluorescence imaging showed the aggregates to be
bright red in
color (Figures 39A, B). Under crossed polarizers, the same aggregates showed
yellow-
brown color (Figure 39C). At a loading of 6 wt.% C6o, the average diameter of
the highly
spherical aggregates of Figure 40 was 30 Vim. These aggregates were relatively
uniform
in size distribution and they had highly ordered structures with deep reddish-
brown color
under crossed polarizers.
Optical microscopy observation of films cast from solutions with high
solubilized fullerene loading (>_ 7 wt.% C6o or Coo in PPQ;o-b-PS;oo) showed
the
coexistence of the discrete spherical aggregates observed at smaller fullerene
loading with
needle-like and continuous fullerene phases. Optical micrographs of PPQ;o-b-
PS3oo
copolymer with 8 and 10 wt.% solubilized C6o are shown in Figure 41. In
addition to
spherical aggregates with average diameters in the 10-20 pm range. large
needle-like
phases (up to 10-20 p,m wide x 200 um long) characteristic of the pure Cbo
were also
observed.
Figure 42 shows the average aggregate diameter, measured from the
optical and fluorescence micrographs, as a function of fullerene loading in
the four
different fullerene/PPQ-PS systems. One main feature of the data was that at
all fullerene
loadings, C~o/PPQ;o-b-PS3oo aggregates had the largest sizes. However. there
was no
clear difference in size between the Coo - and Cbo - containing aggregates of
PPQ~o-b-
PS3oo. These results suggested that there was both an effect of fullerene size
on the
fullerene/PPQ-PS aggregates size (C~o > C6o) as well as a dependence on the
rod-like
block length (PPQ;o-b-PS3oo > PPQ~o-b-PS3oo). Another notable feature of the
data was
the trend of aggregate size with fullerene loading. Increase of diameter with
encapsulated
fullerene amount was observed to peak at about 60-70 mg/g which was followed
by a
factor of 2-3 decrease in size at fullerene loadings greater than 70 mg/g. The
apparent 70-
mg/g transition point may be regarded as the encapsulation capacity of the
fullerenes in
the block copolymer assemblies:.that is, the maximum fullerene loading level
where
complete sequestering inside the spherical block copolymer aggregates is
ensured as
evidence by the morphological observations (Figures 38-41 ). Since this
loading level (70
mg/g) was much smaller that the amount of fullerene that could be solubilized
(200 mg/g)
as determined by solution absorption spectroscopy, this raised questions about
the origin
for this difference. One possibility was that the excess fullerene molecules
outside the
spherical aggregates (see for example Figure 41 ) were originally solubilized
inside the
CA 02324140 2000-09-15
WO 99/47570 - 61 - PCT/US99/05940
nonspherical aggregates (tubules, lamellae, doughnuts) which were
distabiIized. Another
possibility was that some of the fullerene molecules in solution exhibited
colloidal
interactions with the block copolymer molecules and micelles.
The aggregation number N° of the self organized fullerene/PPQ-PS
assemblies was estimated from optical and fluorescence micrographs taken over
large
areas in conjuction with mass balance. For example, for the 6 wt.% C6o/PPQ;o-b-
PS3oo
assembly, 103 spherical aggregates per mm2 area was measured from a
photomicrograph
taken from a 0.2 mg sample covering a 5 cm2 area. This information translated
to 9.6x 10-
~' mole PPQ;o-b-PS3oo diblock/aggregate or N° = 6x 109. Furthermore,
the 6 wt.% Cbo or
64 mg/g encapsulated was equivalent to 3.7 Cbo molecules per PPQ;o-b-PS3oo
diblock
chain which in combination with N° meant that about 2.2x10°
fullerene-Cbo molecules
were encapsulated inside each aggregate of Figure 40. Similar estimates of the
number of
C6o encapsulated in the PPQ;o-b-PS3oo spherical micelles at 0.1 and 3 wt.%
fullerene
loading were 4x 1 O8 and 2x 1 O9, respectively. Since a similar estimate of No
for the empty
PPQ;o-b-PS3oo was 1.5x108, these results suggested that fullerene
solubilization and
encapsulation enhanced the aggregation number by factors of 2.7, 13, and 150
respectively at 0.1, 3, and 6 wt.% C6o loading. Although such an enhancement
of N° was
qualitatively consistent with the predictions of current theories for
solubilization by
micelles formed by coil-coil block copolymer (Nagarajan et al.,
Macromolecules,
22:4312 et seq. (1989); Nagarajan et al., J. Chem. Phvs., 90:5843 et seq.
(1989); Hurter et
al., Macromolecules, 26:5030 et ~eq. (1993); Hurter et al., Macromolecules,
26:5592 et
seq. { 1993 ); Linse, Macromolecules, 27:2685 et seg. ( 1994); Cogan et al.,
Langmuir,
8:429 et seq. ( 1992); and Xing et al., Macromolecules, 30: I 711 et seq. (
1997), which are
hereby incorporated by reference),~'~ ~ it remains to establish their
applicability to the
unusually large micelles of PPQ-PS block copolymers. Compared to the typical
N°
values of 50-100 for coil-coil block copolymer micelles (Solvents and Self
Organization
of Polymers, Webber et al., Eds., Kluwer Academic Publishers, Dordrecht, The
Netherlands (1996), which is hereby incorporated by reference), the
aggregation number
of the present PPQ-PS rod-coil block copolymer micelles was about 6 to 7
orders of
magnitude larger.
To further shed light on the nature of PPQ-PS aggregates with
encapsulated fullerenes, differential scanning calorimetry (DSC) was done on
fullerene-
Cbo/PPQ;o-b-PS3oo aggregates and control samples of pure C6o, PS homopolymer,
C6o/PS
blend, and C6o/poly(methylmethacrylate) blend. Figure 43A shows the DSC scans
of PS
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WO 99/47570 - 62 - PCT/US99/05940
homopolymer (curve 1, the first and subsequent scans were identical),
revealing a glass
transition (To) at 373 K which was in accord with literature values. The
repeated DSC
scans of C6o were identical (curve 2) to that shown in Figure 43A. The
observed sharp
endotherm at 259 K has previously been seen and assigned to the orientational
phase
transition of C6o from the simple cubic (sc) crystalline form which exists
below 259 K to
the face-centered cubic (fcc) crystalline form above 259 K (Dresselhaus et
al., Science of
Fullerenes and Carbon Nanotubes, Academic Press, San Diego, CA ( 1996), which
is
hereby incorporated by reference). The PPQ homopolymer does not exhibit any
DSC
transitions below 673 K. Also shown in Figure 43A is the first DSC scan of 3
wt.%
C6o~PPQso-b-PS3oo (curve 3) which revealed two second-order transitions with
onset
temperatures at 273 and 375 K, respectively. These two transition temperatures
shifted
slightly during subsequent scans, 269 and 374 K for the second run and 282 and
374 K
for the third scan. It is noteworthy that the sc->fcc phase transition of pure
C6o at 259 K
was not observed in the DSC scan of C6o/PPQ;o-b-PS3oo aggregates. The
aggregate
transition at 374-375 can be easily interpreted as the TQ of the PS block
{Polymer
Handbook, Brandrup et al., Eds., 3'd ed., Wiley, New York, Chapt. V, pp. 77-86
(1989),
which is hereby incorporated by reference).38 However, the aggregate second-
order
transition near 273 K was new and must be carefully assigned.
The DSC scan of a 1 wt.% C6a/PS sample is shown in Figure 43B,
revealing two second-order transitions at 274 and 373 K during the first run.
The 373-K
transition corresponded to the To of PS. The transition at 274 K shifted
slightly to 270 K
in subsequent scans. Similarly, the repeated DSC scans of C6o dispersed in
poly(methylmethacrylate) (PMMA) {~l wt % C6o) gave a second-order transition
at 270
K as well as the To transition of the polymer at 377 K (Polymer Handbook.
Brandrup et
al., Eds., 3'd ed., Wiley, New York, Chapt. V, pp. 77-86 (1989), which is
hereby
incorporated by reference)3g. The characteristic sc-~fcc crystalline
transition of pure Cbo
was not observed in either of the DSC scans of this fullerene in an amorphous
polymer
matrix (PS or PMMA). These results suggested that the new second-order
transition at
270 K in the DSC scan of Cbo/PPQ;oPS3oo aggregates was characteristic of
isolated or
amorphous Cbo dispersed in a polymer matrix. From these results it can also be
concluded
that the C6o molecules encapsulated inside the block copolymer micelles were
not
crystalline and that at least some of them were close to and homogeneously
dispersed in
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the PS block. This also supported the micellar mechanism of fullerene
solubilization and
encapsulation by PPQ-PS aggregates.
In addition, TGA thermograms of block copolymer samples PPQ;o-b-PS3oo
(54c) and PPQ,o-b-PS3oo (54f] and the PPQ and PS homopolymers at 10
°C/minute in N2
are shown in Figure 46.
These studies of the morphology of self organized fullerene/diblock
copolymer aggregates in comparison with the empty micelles clearly revealed
the
profound effects of fullerene solubilization and encapsulation on the physical
size and
aggregation number. The observed increase in diameter of the fullerene/PPQ-PS
spherical aggregates correlated well with an amount of fullerene loading up to
70 mg/g
I 5 and the underlying accommodation of more diblock chains per micellar
aggregate. The
previously discussed solubilization results together with the morphological
observations
and DSC results supported the model structure of the rod-coil block copolymer
micelles
with encapsulated fullerene molecules shown in Figure 34. This structure
assumed that
the hollow cavity as well as the inner PS shell were partially filled with
fullerene
molecules whereas the rigid-rod PPQ outer shell was free of fullerenes.
Effect of Encapsulated Fullerenes on Block Copolymer Assemblies.
The intrinsic electroactive and photoactive properties of PPQ-PS block
copolymers (Agrawal et al., Macromolecules, 26:895-905 (1993); Agrawal et al.,
Chem.
Mater.. 8:579-589 (1996); Agrawal et al., J. Phys. Chem., 96:2837 et seq.
(1992); Jenekhe
et al., Chem. Mater., 9:409 et seg. ( 1997), which are hereby incorporated by
reference)
were exploited to probe molecular packing and the effects of encapsulated
solubilizates
on the molecular packing of the block copolymer assemblies. In particular, the
focus was
on the molecular packing of the conjugated rigid-rod PPQ block whose relative
fluorescence quantum yield was orders of magnitude larger than those of the
fullerenes
(Cbo, Coo). It was also noteworthy that the emission bands of the fullerenes
were in the
near infrared region, which was far away from where PPQ-PS aggregates emit, so
that
there was no possible interference from their fluorescence bands. As a
reference
chromophore, the photoluminescence emission (PL) and excitation (PLE) spectra
of the
isolated PPQ;o-b-PS3oo chain in the form of a dilute blend film [0.1 wt %
PPQ;o-b-PS3oo in
polyethylene oxide) (PEO)] was investigated. The PL spectrum of such an
isolated
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PPQso-b-PS3oo chain had a peak at 466 nm (when excited at 380 nm) and a PLE
spectrum
with an absorption maximum at 390 nm when monitoring emission at 460 nm.
Figure 44A shows the PL and PLE spectra of a film of spherical PPQ;o-b-
PS3oo aggregates without any fullerene. These spherical aggregate spectra were
very
similar to those of the isolated PPQ;o-b-PS3oo single chain except that they
were slightly
blue shifted. The aggregate PL spectrum had a peak at 454 nm whereas the PLE
spectrum had a peak at 388 nm. Incorporation of fullerene molecules in PPQ;o-b-
PS3oo
aggregates resulted in dramatic changes in the aggregate photophysical
properties as
exemplified by Figure 44B which shows the PL and PLE spectra of a film of 1
wt.%
Cbo~'PQso-b-PS3oo. Two emission bands at 430 and 600 nm were observed in the
PL
spectrum. The 430-nm emission band was blue-shifted compared to that of
spherical
PPQ;o-b-PS3oo aggregate without any C6o since the excitation spectra were
similar
whereas the 600-nm band was new. The PLE spectrum monitored at 480 nm gave an
absorption band centered at 388 nm, slightly narrower (full width at half
maximum of 62
versus 72 nm) than the spectrum of the empty PPQ;o-b-PS3oo aggregates.
However, the
PLE spectrum monitored at 600 nm showed entirely new absorption
characteristics with
peaks at 426 and 480 nm. These results suggested that the 430-nm and 600-nm
emission
bands come from different emitting species. Direct excitation of the fullerene-
PPQ;o-b-
PS3oo aggregate at 480 nm gave an emission band that was the same as the 600-
nm PL
band. Figure 44C shows the PL and PLE spectra of aggregates of 5 wt.%
Cbo/PPQ;o-b-
PS3oo. Only one emission band at 600 nm was observed regardless of the
excitation
wavelength. The corresponding PLE spectrum monitored at 600 nm showed
absorption
peaks at 429 and 506 nm. In fact, similar investigations of other compositions
of
encapsulated C6o in PPQ;o-b-PS3oo between 0.1 and 5 wt.% of C6o showed a
progressive
evolution of the photophysical properties with fullerene loading.
These spectral features of the absorption and emission properties of
fullerene/PPQ-PS assemblies can best be understood within the framework of H-
and J-
aggregation (Kasha, Radiation Research, 20:55 et seg. ( 1963); Czikkely et
al., Chem.
P_ hys., 6:11 et seq. ( 1970); Fidder et al., Phys. Stat. Sol.. B., 188:285 et
seg. ( 1995);
Hochstrasser et al., Photochem. Photobiolo~y, 3:317 et seq. ( 1964); Chen et
al., J. Am.
Chem. Soc., 118:2584 et seq. (1996); Gratzel et al., Chem. Phys., 193:1 et
seq. (1995);
Spano et al., Phi s. Rev., 40:5783 et seg. ( I 989), which are hereby
incorporated by
reference) of the rod-like PPQ blocks. The 454-nm emission band with
corresponding
388-nm absorption band of the hollow PPQ;oPS3oo micelles were blue-shifted
from those
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WO 99/47570 - 65 - PCTNS99/05940
~ of the isolated PPQ-PS chromophore, suggesting the occurrence of H-
aggregation of the
fluorescent PPQ blocks. The further blue shift and narrowing of the 430-nm
emission
band at 1 wt.% Cbo loading suggested that the H-aggregates of PPQ blocks were
modified
compared to the empty PPQ;o-b-PS3oo assemblies. The significantly red-shifted
absorption (PLE) and emission bands at 506 and 600 nm, respectively, in the 5
wt.%
C6o/PPQ;o-b-PS3oo assemblies compared to the isolated PPQ-PS chromophore were
characteristic of J-aggregation of the conjugated PPQ blocks. The progressive
evolution
of the PLE and PL spectra with increasing amounts of fullerene molecules
incorporated
into the PPQ-PS assemblies could thus be understood as a consequence of the
progressive
transformation of the H-aggregates of PPQ blocks in the original empty hollow
micelles
1 S into all J-aggregates at 5 wt.% C6o loading which corresponds to 3.1 C6o
molecules per
PPQ;o-b-PS3oo copolymer chain. Such a fullerene solubilization and
encapsulation
induced transformation of PPQ-PS rod-coil diblock copolymer chains in H-
aggregates to
J-aggregates is illustrated in Figure 45.
These results further confirmed the profound effects of fullerene
solubilization and encapsulation on the aggregation behavior of the rod-coil
diblock
copolymers and their micellar assemblies. The strong interaction of the
fullerenes with
PS blocks and consequently on the molecular packing of the PPQ blocks also
supported
the micellar nature of the hollow spherical aggregates of PPQ-PS rod-coil
block
copolymers. Although the possible contribution of some vesicle-like trapping
to the
fullerene solubilization in PPQ-PS assemblies could not be completely ruled
out, ail the
present results supported micellar solubilization as the dominant mechanism.
For
example, trapped molecules in bilayer vesicles do not usually influence the
molecular
packing of the hollow spheres (Vesicles, Rosoff, Ed., Marcel Dekker, New York
(1996),
which is hereby incorporated by reference). The J-aggregation of conjugated
PPQ blocks
in the spherical fullerene/PPQ-PS block copolymer assemblies confirmed that
the
fullerene molecules were excluded from the outer shell PPQ blocks (Figures 34
and 45).
The observed J-aggregation of these self organized fullerene-block
copolymer micelles implied that they were highly ordered (Kasha, Radiation
Research,
20:55 et seg. ( 1963); Czikkely et al., Chem. Phys., 6:11 et seg. ( 1970);
Fidder et al., Phvs.
Stat. Sol. B., 188:285 et seq. ( 1995); Hochstrasser et al., Photochem.
Photobiolo~v, 3:317
et seg. { 1964); Chen et al., J. Am. Chem. Soc., 118:2584 et seq. ( 1996);
Gratzel et al.,
Chem. Phys., 193:1 et seq. (1995); Spano et al., Phys. Rev., 40:5783 et seq.
(1989), which
are hereby incorporated by reference). This was in accord with the previously
discussed
CA 02324140 2000-09-15
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polarized optical microscopy observations (Figures 38-40). Together, these
results
provided detailed knowledge of molecular packing and of the effects of
solubilizates on
the molecular packing of block copolymer micelles, demonstrating the potential
of optical
and photoelectronic techniques for characterizing micellar aggregates
containing
electroactive and photoactive blocks. The fullerene-block copolymer assemblies
per se
are also of potential broad interest as advanced mesoscopic materials with
possible
cooperative electronic and optical properties similar to molecular aggregates
of dyes
(Kasha, Radiation Research, 20:55 et seq. ( 1963); Czikkely et al., Chem. Ph
~~s., 6: I I et
seq. (1970); Fidder et al., Phys. Stat. Sol. B., 188:285 et seq. (1995);
Hochstrasser et al.,
Photochem. Photobioloey, 3:317 et seg. (1964); Chen et al., J. Am. Chem. Soc.,
I 18:2584
et seq. ( 1996); Gratzel et al., Chem. Phys., 193:1 et seq. (1995); Spano et
al., Ph s. Rev.,
40:5783 et seg. ( I 989), which are hereby incorporated by reference) and
composite
properties that combine the features of the fullerenes and conjugated polymers
(Dresselhaus et al., Science of Fullerenes and Carbon Nanotubes, Academic
Press, San
Diego, CA (1996); Hirsch, The Chemistry of the Fullerenes, Georg Thieme
Verlag,
Stuttgart ( I 994); The Chemical Physics of Fullerenes I 0 (and 5) Years
Later, Andreoni,
Ed., Kluwer Academic Publishers, Dordrecht, The Netherlands ( 1996); Hebard et
al.,
Nature, 350:600-601 (1991); Zakhidov et al., Phys. Lett. A, 205:317-326
(1995); Kajii et
al., Synth, Met., 86:2351-2352 (1997); Sariciftci et al., Science, 258:1474-
1476 (1992);
Sariciftci et al., Appl. Phys. Lett., 62:585-587 (1993); Wang et al., Nature,
356:585-587
(1992); Wang et al., J. Phys. Chem., 101:5627-5638 (1997), which are hereby
incorporated by reference). Development of methods to order or crystallize or
dope the
encapsulated fullerenes inside the block copolymer micelles could open up many
other
possible applications of these supramolecular materials.
Example 6 - Preparation of a Mesoporous Solid
The self organization of hollow spherical micelles from a rod-coil block
copolymer system in a selective solvent for the flexible-coil block and their
long-range,
close-packed. self ordering into iridescent, ordered mesoporous solids is
reported. This
hierarchical self assembly approach to mesoporous solids represents a non-
template
strategy (Figure 12). The micellar structure, consisting of a hollow core, a
rod-like inner
shell, and a flexible-coil outer corona, had a diffuse corona characteristic
of coil-coil
block copolymer micelles (McConnell et al., Phvs Rev. Lett., 71:2102-2105
(1993);
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WO 99/47570 - 67 - PCT/US99/05940
McConnell et al., Macromolecules, 28:6754-6764 (1995); McConnell et al.,
Macromolecules, 30:435-444 (1997); McConnell et al., Phys. Rev. E., 54:5447-
5455
( 1996); Halperin et al.. Adv. Polvm. Sci., 100:31-71 ( 1992); Forster et al.,
Adv. Mater.,
10:195-217 ( 1998); Zhang et al., J. Am. Chem. Soc., 118:3168-3181 ( 1996);
Zhang et al.,
Science, 268:1728-1731 ( 1995), which are hereby incorporated by reference).
Steric
repulsion driven self ordering and crystallization of coil-coil diblock
micelles and their
demonstrated control through the corona block length (McConnell et al., Pas
Rev. Lett.,
71:2102-2105 (1993); McConnell et al., Macromolecules. 28:6754-6764 (1995);
McConnell et al., Macromolecules, 30:435-444 (1997); McConnell et al., Phvs.
Rev. E.,
54:5447-5455 (1996)) are thus also viable options here.
The rod-coil block copolymer system investigated was
poly(phenylquinoline)-block-polystyrene (PPQmPS", where m and n are the number
of
repeat units of the respective blocks) in carbon disulfide (CS?), which is a
selective
solvent for PS block. The specific rod-coil block copolymer compositions
studied were
PPQIOPS3oo, PPQioPS~ooo, and PPQSOPS2~o which were either identical to those
previously reported (Jenekhe et al., Science, 279:1903-1907 (1998), which is
hereby
incorporated by reference) or similarly made. The basic synthetic chemistry
was that
associated with the rigid, rod-like conjugated PPQ homopolymer (Agrawal et
al.,
Macromolecules, 26:895-905 (1993); Agrawal et al., Chem. Mater., 8:579-589
(1996),
which are hereby incorporated by reference), which is highly fluorescent and
has
nonlinear optical properties (Agrawal et al., J. Phys. Chem., 96:2837-2843
(1992);
Jenekhe et al., Chem. Mater., 9:409-412 ( 1997), which are hereby incorporated
by
reference).
Solutions of the rod-coil block copolymers (0.005 to I .0 wt.%) in CS2 and
monolayer and multilayer films cast from them at room temperature (25
°C) were
investigated. Direct optical, fluorescence, and scanning electron microscopy
observations
of discrete micellar aggregates and their higher order assembly into large-
scale periodic
microstructures were made. The possible effects of both the local structure of
the
micellar building block and the large-scale periodic microstructure on the
spontaneous
emission of the PPQ chromophores of the rod-coil blocks were probed by
previously
described steady-state and time-resolved photoluminescence techniques (Osaheni
et al., J.
Am. Chem. Soc., 117:7389-7398 ( I 995); Jenekhe et al., Science, 265:765-768 (
1994),
which are hereby incorporated by reference).
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WO 99/47570 - 68 - PCTNS99/05940
From a small angle neutron scattering study of poly
(p-phenylene)-block-polystyrene in a selective solvent for PS, spherical
micelles of the
conventional dense core-diffuse corona structure with a core diameter of 3 to
5 nm were
observed. These rod-coil diblocks and star homopolymers formed ordered
microporous
films by an unclear phase separation mechanism.
The experimental results show that rod-coil block chains solved the steric
problem associated with packing rod-like blocks radially into a sphere in a
surprising way
not anticipated by theory: a hollow sphere. Fluorescence photomicrographs of
micelles
formed by PPQ~oPS3~ in CS2 provided evidence of hollow spheres (Figures 47A
and
47B). The shape of the discrete micellar aggregates looked somewhat like red
blood cells
because of distortion and partial collapse of the hollow spheres due to
drying. Additional
microscopic observations under bright field and crossed polarizers confirmed
that the
micelles formed by all three copolymer samples had approximate diameters of 3
to ~ p,m.
Polarized optical microscopy indicated that the micelles were highly ordered.
This
ordering originated from orientationally ordered radial packing of the rigid,
rod-like
blocks; micellar aggregates of coil-coil block copolymers lack such order
(Webber et al.,
Solvents and Self Organization of Polymers, Kluwer Academic, Dordrecht (1996);
Webber, J. Phys. Chem. B, 102:2618-2626 (1998); Tuzar et al., in Surface and
Colloid
Science, 15:1-83, Plenum, New York (1993); Halperin et al., Adv. Polym. Sci.,
100:31-71
( 1992); Forster et al., Adv. Mater:, 10:195-217 ( 1998); Zhang et al., J. Am.
Chem. Soc.,
118:3 I 68-3181 ( 1996); Zhang et al., Science, 268:1728-1731 ( 1995), which
are hereby
incorporated by reference). The hollow spherical structure of these rod-coil
block
micelles in CSz was, however, different from that formed by the same
copolymers in
trifluoroacetic acid/dichloromethane (a selective solvent for the rod-like
blocks) (see
Example 3; Jenekhe et al., Science, 279: i 903-1907 ( I 998); Chen et al.,
Lan,~muir,
12:2995-3002 ( 1996), which are hereby incorporated by reference) in that here
the
solvated coil-like blocks were on the convex side. A profound consequence of
the
stiffness asymmetry of a rod-coil block copolymer was that the same
macromolecule in
two different selective solvents self organized into two qualitatively
different colloidal
particles: hollow hard spheres and hollow soft spheres.
Self ordering of these hollow soft spheres into two-(2-D) and three-
dimensional (3-D) periodic structures was studied by optical and electron
microscopy of
micellar films cast from rod-coil block copolymer solutions of varying initial
CA 02324140 2000-09-15
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concentrations in ways similar to prior studies of colloidal crystallization
of polymer latex
spheres (Kose et al., Colloid Interface Sci., 46:460 ( 1974); Hachisu et al.,
Nature,
283:188-189 (1980); Clark et al., Nature, 281:57-60 (1979); Pieranski et al.,
Contemn.
Phvs., 24:25-73 (1983); Pusey et al., Nature, 320:340-342 (1986); Bartlett et
al., Phys.
Rev. Lett., 68:3801-3804 (1992); van Blaaderen et al., Nature, 385:321-324
(1997);
Weissman, et al., Science, 274:959-960 (1996), which are hereby incorporated
by
reference). Only discrete. non-aggregated, micelles, were obtained from very
dilute
solutions between 0.005 to 0.01 wt.% (Figures 47A and 47B). However, even at
0.01
wt.%, the particle number density was sufficiently high for the onset of 2-D
micellar
ordering to be visible in regions of a monolayer film (Figure 47B, arrows).
Micellar films
1 S cast from 0.5 wt.% had a controllable thickness of about 4.5 to 35 pm and
consisted of
stacks of one to eight layers of hexagonally close-packed (hcp) 2-D lattices
of spherical
air holes in a polymeric matrix. An example is the ~27-pm thick micellar film
of PPQ,o-
b-PS3oo which revealed a 2-D hcp structure when viewed from the top (Figure
47C) and
was visually highly iridescent at various reflection angles akin to a credit
card hologram.
The air holes revealed by carefully peeling off part of the top layer with an
adhesive tape
largely reflected the original hollow spherical micelles. The moderate
mechanical
properties of these self ordered micellar films suggested that significant
interdigitation of
the polystyrene coronal chains occurred between the micellar building blocks
of the
microporous solid.
Defect-free microstructure of the periodic microporous films of all three
block copolymers covered areas as large as 1 cm' and varied with composition
and
molecular weight. From the polarized optical and scanning electron (SEM)
micrographs
of micellar films of PPQ;o-b-PS2aoo (Figures 48A to C), 2-D hcp lattice of
spherical air
holes having a diameter (D) of 3.4 ~ 0.2 gm and a center-to-center hole
periodicity (p) of
4.4 ~ 0.2 gm were observed from the top layer. The ~31 pm film consisted of
seven
layers of air hole lattices of which the top layer was clearly open (Figures
48B and C).
The progressive decreases of the hole diameter and periodicity of the
microstructure with
the PS block length were approximately linear (Figure 48D), decreasing to 2.6
~ 0.2 and
2.8 t 0.2 pm, respectively, for micellar films of PPQ,o-b-PS3oo. The minimum
wall
thickness h (= p-D), which was in the range of 0.2 to 1.0 pm for the three
copolymer
compositions, also varied linearly with the PS coronal chain length. Evidence
of the 3-D
order of these multilayer films included their colorful iridescence (Wijnhoven
et al.,
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WO 99/47570 - 70 - PCTNS99/05940
Science, 281:802-804 (1998); Kose et al., Colloid Interface Sci., 46:460-469
(1974);
Hachisu et al., Nature, 283:188-189 (1980); Clark et al., Nature, 281:57-60
(1979);
Pieranski et al., Contemp. Phvs., 24:25-73 (1983); Pusey et al., Nature,
320:340-342
(1986); Bartlett et al., Phys. Rev. Lett., 68:3801-3804 (1992); van Blaaderen
et al.,
Nature, 385:321-324 ( 1997); Weissman et al., Science, 274:959-960 ( 1996),
which are
I 0 hereby incorporated by reference) and observation of ordered arrays of the
air holes when
multilayer films were viewed from the side or by sequential removal of layers
from the
top. Distinction between ABCABC- or ABABAB-type stacking of layers and hence
whether the 3-D lattice was fcc or hcp could not be established.
I 5 Example 7 - Preparation of Microporous Films Containing Fullerenes
Addition of small amounts {< 20 mg/g rod-coil block) of fullerene (C~o or
Cbo) into the solutions in CS2 (see Example 6) significantly modified the
microstructural
parameters of the ordered microporous films (Figure 49). Although these
fullerene-
containing micellar films had superior iridescence colors compared to similar
20 microporous films without fullerene, they were more brittle with visible
cracks. The hole
diameter and periodicity decreased with the amount of fullerene loading, up to
29 and
25% reductions, respectively, at 10 mg Coo /g PPQ,o-b-PS3oo (Figure 49B). The
wall
thickness increased slightly with fullerene loading. Similar effects of
fullerene Coo or Cbo
on self organized microporous films of PPQ,o-b-PSiooo and PPQ;o-b-PS2ooo were
25 observed. Self assembly of microporous films was no longer observed in any
of the three
rod-coil block copolymers at high fullerene loading (> 20 mg/g). These results
suggested
that the fullerene was incorporated within the PS corona of the micellar
building blocks as
expected from their mutual compatibility (Jenekhe et al., Science, 279:1903-
1907 (1998),
which is hereby incorporated by reference). These findings also suggested a
simple way
30 of controlling the functional properties of the microporous materials
independently of
copolymer architecture and composition.
Because of their spatially periodic variation of refractive index, these self
organized ordered microporous materials with or without fullerenes are
promising, easy
to produce, photonic band gap structures (Wijnhoven et al., Science, 281:802-
804 ( 1998);
35 Yablonovitch, J. Opt. Soc. Am. B., 10:283-295 (1993); Joannopoulos et al.,
Nature,
386:143-145 (1997); Martorell et al., Phys. Rev. Lett., 65:1877-1880 (1990);
Miguez et
al., Appl. Phys. Lett., 71:1148-1150 (1997), which are hereby incorporated by
reference).
These periodic dielectric composites of air holes (refractive index no = 1 )
and rod-coil
CA 02324140 2000-09-15
WO 99/47570 PCTNS99/05940
- 71 -
block walls (n° = 1.6 for PS, 1.8 for PPQ) have a high refractive index
contrast. The
higher index contrast in fullerene-containing micellar films, Coo (n° =
1.94) and C6o(no =
2.00-2.12) (Dresselhaus et al., Science of Fullerenes and Carbon Nanotubes,
Academic
Press, San Diego, CA ( 1996), which is hereby incorporated by reference), can
explain
their superior optical properties. However. the present hole diameters and
periodicities
I 0 were comparable to infrared (IR} wavelengths. Reductions in D and p to
sizes
comparable to visible wavelengths are desirable for some photonic and
optoelectronic
applications (Yablonovitch, J. Opt. Soc. Am. B., 10:283-295 (1993);
Joannopoulos et al.,
Nature, 386:143-145 (1997); Martorell et al., Phvs. Rev. Lett., 65:1877-1880
{1990);
Miguez et al., Appl. Phvs. Lett., 71:1148-1150 ( I 997), which are hereby
incorporated by
reference).
Significant modification of the spontaneous emission of the PPQ blocks in
the self assembled, periodic microporous films. compared to the isolated
chromophores;
dispersed in a matrix of polyethylene oxide) (PEO), was observed by
photoluminescence
emission (PL) and excitation (PLE) spectroscopies (Figure 50). Isolated PPQ
chromophores of PPQ~o-b-PS3oo rod-coil block had emission and excitation bands
at 466
and 393 nm, respectively. In contrast, the micellar films of PPQio-b-PS3oo
cast from a 0.5
wt.% solution had blue-shifted PL and PLE spectra with peaks at 437 and 388
nm,
respectively, (Figure SOA), and absorption band observed in the PLE was more
narrow.
Time-resolved PL decay dynamics of the fluorescent PPQ blocks as isolated
chains in
PEO revealed two lifetimes (1.1 ns (30%) and 4.7 ns (70%)) versus one lifetime
(0.93ns)
(Figure SOB) in the micellar films. This represented a large reduction in the
excited state
lifetime of PPQ chromophores in the microporous micellar films. Because the
emission
band was far removed from photonic band gaps of these microporous films, which
were
expected to be in the IR region, the large-scale periodic microstructure was
ruled out as
the origin of the observed modification of photophysical properties. The
decrease in
lifetime was also the opposite of the predicted effect of a photonic crystal
on spontaneous
emission (Yablonovitch, J. Opt. Soc. Am. B., 10:283-295 (1993); Joannopoulos
et al.,
Nature, 386:143-145 (1997); Martorell et al., Phvs. Rev. Lett., 65:1877-1880
(1990);
Miguez, et al., Appl. Phys. Lett., 71:1148-1 I50 (1997), which are hereby
incorporated by
reference). H-aggregation {Kasha, Radiation Research, 20:55 et seq. (1963);
Hochstrasser et al., Photochem. Photobiolo~y, 3:317 et seg. (1964); Czikkely
et al.,
Chem. Ph ~~s., 6:1 I-14 (1970); Chen et al., J. Am. Chem. Soc., 118:2584 et
seq. (1996),
which are hereby incorporated by reference) of the PPQ blocks and hence the
local
CA 02324140 2000-09-15
WO 99/47570 - 72 - PCT/US99/05940
structure of the micellar building blocks best explained the observed
photophysical
properties. H-aggregation of the rigid rod-like blocks implied that they were
orientationally aligned close to the radial direction in the spherical
miceIlar assemblies
(Figure 12). Such an H-aggregation of conjugated molecules can lead to novel
cooperative optical and nonlinear optical properties (Kasha, Radiation
Research, 20:55 et
seq. ( 1963); Hochstrasser et al., Photochem. Photobiolo~y, 3:317 et seq. (
1964); Czikkely
et al., Chem. Phvs., 6:11-14 (1970); Chen et al., J. Am. Chem. Soc., 118:2584
et seq.
( 1996), which are hereby incorporated by reference).
Although the invention has been described in detail for the purpose of
illustration, it is understood that such detail is solely for that purpose,
and variations can
be made therein by those skilled in the art without departing from the spirit
and scope of
the invention which is defined by the following claims.
