Note: Descriptions are shown in the official language in which they were submitted.
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TITLE OF THE INVENTION
IMPROVED PROCESSES BASED ON ATOM (OR GROUP) TRANSFER RADICAL
POLYMERIZATION AND NOVEL (CO)POLYMERS HAVIt1G USEFUL STRUCTURES
AND PROPERTIES
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention concerns novel (co)polymers and a
novel radical polymerization process based on transition
metal-mediated atom or group transfer polymerization ("atom
transfer radical polymerization").
Discussion of the Background
Living polymerization renders unique possibilities of
preparing a multitude of polymers which are well-defined in
terms of molecular dimension, polydispersity, topology,
composition, functionalization and microstructure. Many
living systems based on anionic, cationic and several other
types of initiators have been developed over the past 40 years
(see O.W. Webster, Science, 251, 887 (1991)).
However, in comparisdn to other living systems, living
radical polymerization represented a poorly answered challenge
prior to the present invention. It was difficult to control
the molecular weight and the polydispersity to achieve a
highly uniform product of desired structure by prior radical
polymerization processes.
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On the other hand, radical polymerization offers the
advantages of being applicable to polymerization of a wide
variety of commercially important monomers, many of which
cannot be polymerized by other polymerization processes.
Moreover, it is easier to make random copolymers by radical
polymerization than by other (e.g., ionic) polymerization
processes. Certain block copolymers cannot be made by other
polymerization processes. Further, radical polymerization
processes can be conducted in bul}:, in solution, =n suspension
or in an emulsion, in contrast to other polymerization
processes.
Thus, a need is strongly felt for a radical
polymerization process which provides (co)polymers having a
predetermined molecular weight, a narrow molecular weight
distribution (low "polydispersity"), various topclogies and
controlled, uniform structures.
Three approaches to preparation of controlled polymers in
a "living" radical process have been described (Greszta et al,
Macr'omolecules, 27, 638 (1994)). The first approach involves
the situation where growing radicals react reversibly with
scavenging radicals to form covalent species. The second
approach involves the situation where growing radicals react
reversibly with covalent species to produce persistent
radicals. The third approach involves the situation where
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growing radicals participate in a degenerative transfer
reaction which regenerates the same type of radicals.
There are some patents and articles on living/controlled
radical polymerization. Some of the best-controlled polymers
obtained by "living" radical polymerization are prepared with
preformed alkoxyamines or are those prepared in situ (U.S.
Patent 4,581,429; Hawker, J. Am. Chem. Soc., 116, 11185
(1994); Georges et al, WO 94/11412; Georaes et al,
Macromolecules, 26, 2987 (1993)). A Co-containing complex has
been used to prepare "living" polyacrylates (Wayland, B. B.,
Pszmik, G., Mukerjee, S. L., Fryd, M. J. Am. Chem. Soc., 116,
7943 (1994)). A "living" poly(vinyl acetate) can be prepared
using an Al(i-Bu),: Bpy:TEMPO initiating system (Mardare et al,
Macromolecules, 27, 645 (1994)). An initiating system based
on benzoyl peroxide and chromium acetate has been used to
conduct the controlled radical polymerization of methyl
methacrylate and vinyl acetate (Lee et al, J. Chem. Soc.
Trans. Faraday Soc. I, 74, 1726 (1978); Mardare et al, Polym.
Prep. (ACS), 36(1) (1995)).
However, none of these "living" polymerization systems
include an atom transfer process based on a redox reaction
with a transition metal compound.
One paper describes a redox iniferter system based on
Ni(O) and benzyl halides. However, a very broad and bimodal
molecular weight distribution was obtained, and the initiator
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efficiency based on benzyl halides used was about 1-2% or less
(T. Otsu, T. Tashinori, M. Yoshioka, Chem. Express 1990,
5(10), 801). Tazaki et al (Mem. Fac. Eng., Osaka City Univ.,
vol. 30 (1989), pages 103-113) disclose a redox iniferter
system based on reduced nickel and benzyl halides or xylylene
dihalides. The examples earlier disclosed by Tazaki et al do
not include a coordinating ligand. Tazaki et al also disclose
the nolymerization of styrene and methyl methacrylate using
their iniferter svstem.
These systems are similar to the redox initiators
developed early (Bamford, in Comprehensive Polymer Science,
Allen, G., Aggarwal, S. L., Russo, S., eds., Pergamon: Oxford,
1991, vol. 3, p. 123), in which the small amount of initiating
radicals were generated by redox reaction between (1) RCHX, or
RCX, (where X = Br, Cl) and (2) Ni(0) and other transition
metals. The reversible deactivation of initiating radicals by
oxidized Ni is very slow in comparison with propagation,
resulting in very low initiator efficiency and a very broad
and bimodal molecular weight distribution.
,
Bamford (supra) also discloses a Ni[P(OPh)3]4a/CCl4 or CBr4
system for polymerizing methyl methacrylate or styrene, and
use of Mo(CO)n to prepare a graft copolymer from a polymer
having a brominated backbone and as a suitable transition
metal catalyst for CC14, CBr4 or CC1,CO:Et initiators for
polymerizing methyl methacrylate. Organic halides other than
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CC1, and CBr4 are also disclosed. Mn2 (CO),o/CC14 is taught as a
source of CC1, radicals. Bamford also teaches that systems
such as Mn(acac)3 and some vanadium (V) systems have been used
as a source of radicals, rather than as a catalyst for
transferring radicals.
A number of the systems described by Bamford are "self-
inhibiting" (i.e., an intermediate in initiation interferes
with radical generation). Other systems require coordination
of monomer and/or photoinitiation to proceed. It is further
suggested that photoinitiating systems result in formation of
metal-carbon bonds. In fact, Mn(CO)5C1, a thermal initiator,
is also believed to form Mn-C bonds under certain conditions.
In each of the reactions described by Bamford, the rate
of radical formation appears to be the rate-limiting step.
Thus, once a growing radical chain is formed, chain growth
(propagation) apparently proceeds until transfer or
termination occurs.
Another paper describes the polymerization of methyl
methacrylate, initiated by CC14 in the presence of RuC12(PPh3)3.
However, the reaction does not occur without methylaluminum
bis(2,6-di-tert-butylphenoxide), added as an activator (see M.
Kato, M. Kamigaito, M. Sawamoto, T. Higashimura,
Macromolecules, 28, 1721 (1995)).
U.S. patent no. 5,405,913 (to Harwood et al) discloses a
redox initiating system consisting of Cuii salts, enolizable
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aldehydes and ketones (which do not contain any halogen
atoms), various combinations of coordinating agents for CuII
and Cu', and a strong amine base that is not oxidized by CuII.
The process of Harwood et al requires use of a strong amine
base to deprotonate the enolizable initiator (thus forming an
enolate ion) , which then transfers a single electron to CuII,
consequently forming an enolyl radical and CuI. The redox
initiation process of Harwood et al is not reversible.
In each of the systems described by Tazaki et al, Otsu et
al, Harwood et al and Bamford, polvmers having uncontrolled
molecular weights and polydispersities typical fcr those
produced by conventional radical processes were obtained
(i.e., > 1.5). Only the system described by Kato et al
(Macromolecules, 28, 1721 (1995)) achieves lower
polydispersities. However, the polymerization svstem of Kato
et al requires an additional activator, reportedly beinq
inactive when using CC1õ transition metal and ligand alone.
Atom transfer radical addition, ATRA, is a known method
for carbon-carbon bond formation in organic synthesis. (For
reviews of atom transfer methods in organic synthesis, see
curran, D. P. Synthesis, 1988, 489; Curran, D. P. in Free
Radicals in Synthesis and Biology, tdinisci, F., ed., Kluwer:
Dordrecht, 1989, p. 37; and Curran, D. P. in Comprehensive
Organic Synthesis, Trost, B. M., Fleming, I., eds., Pergamon:
oxford, 1991, Vol. 4, p. 715.) In a very broad class of ATRA,
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two types of'atom transfer methods have been largely
developed. One of them is known as atom abstraction or
homolytic substitution (see Curran et al, J. Org. Chem., 1989,
54, 3140; and Curran et al, J. Am. Chem. Soc., 1994, 116,
4279), in which a univalent atom (typically a halogen) or a
group (such as SPh or SePh) is transferred from a neutral
molecule to a radical to form a new o-bond and a new radical
in accordance with Scheme 1 below:
Scheme 1:
Ri' + Rj-X Ri' + Rl-X
X = I, SePh,...
In this respect, iodine atom and the SePh group were
found to work very well, due to the presence of very weak C-I
and C-SePh bonds towards the reactive radicals (Curran et al,
J. Org. Chem. and J. Am. Chem. Soc., supra). In earlier work,
the present inventors have discovered that alkyl iodides may
induce the degenerative transfer process in radical
polymerization, leading to a controlled radical polymerization
of several alkenes. This is consistent with the fact that
alkyl iodides are outstanding iodine atom donors that can
undergo a fast and reversible transfer in an initiation step
and degenerative transfer in a propagation step (see Gaynor et
al, Polym. Prep. (Am. Chem. Soc., Polym. Chem. Div.), 1995,
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36(1) , 467; Wang et al, Polym. Prep. (Am. Chem. Soc. , Polym.
Chem. Div.), 1995, 36(1), 465; Matyjaszewski et al,
Macromolecules, 1995, 28, 2093). By contrast, alkyl bromides
and chlorides are relatively inefficient degenerative transfer
reagents.
Another atom transfer method is promoted by a transition
metal species (see Bellus, D. Pure & Appl. Chem. 1985, 57,
1827; Nagashima, H. ; Ozaki, Pl. ; Ishii, M. ; Seki, K.;
Washivama, ;=i. ; Itoh, N. J . Org. Chem. 1993, 58 ,464 ; Udding,
J. H. ; Tuijp, K. J. M. ; van Zanden, M. N. A. ; Hiemstra, H. ;
Speckamp, W. N. J. Org. Chem. 1994, 59, 1993; Seilas et al,
Tetrahedron, 1992, 48(9), 1637; Nagashima, H.; Wakamatsu, H.;
Ozaki, N.; Ishii, T.; Watanabe, M.; Tajima, T.; Itoh, K. J.
Org. Chem. 1992, 57, 1682; Hayes, T. K.; Villani, R.; Weinreb,
S. M. J. Am. Chem. Soc. 1988, 110, 5533; Hirao et al, Syn.
Lett., 1990, 217; and Hirao et al, J. Synth. Org. Chem.
(Japan.) , 1994, 52 (3) , 197; Iabal, J; Bhatia, B. ; Nayyar, N. K.
Chern. Rev., 94, 519 (1994); Asscher, t~i. , Vofsi, D. J. Chem.
Soc. 1963, 1887; and van de Kuil et al, Chem. ;=fater., 1994, 6,
1675). In these reactions, a catalytic amount of transition
metal compound acts as a carrier of the halogen atom in a
redox process.
Initially, the transition metal species, t4t", abstracts
halogen atom X from the organic halide, R-X, to form the
oxidized species, M."''X, and the carbon-centered radical R'.
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In the subseauent step, the radical, R', reacts with alkene, M,
with the formation of the intermediate radical species, R-M'.
The reaction between M.'*':C and R-M' results in the target
product, R-M-X, and regenerates the reduced transition metal
species, ML", which further reacts with R-X and promotes a new
redox process.
The high efficiency of transition metal-catalyzed atom
transfer reactions in producing the target product, R-M-X, in
good to excellent yields (often > 90%) may suggest that the
presence of an M,"/Mt"'1 cycle-based redox process can
effectively compete with the bimolecular termination reactions
between radicals (see Curran, Synthesis, in Free Radicals in
Synthesis and Biology, and in Comprehensive organic Synthesis,
supra). However, the mere presence of a transition metal
compound does not ensure success in telomerization or
polymerization, even in the presence of initiators capable of
donating a radical atom or group. For example, Asscher et al
(J. Chem. Soc., supra) reported that copper chloride
completely suppresses telomerization.
Furthermore, even where a transition metal compound is
present and telomerization or polymerization occurs, it is
difficult to control the molecular weight and the
polydispersity (molecular weight distribution) of polymers
produced by radical polymerization. Thus, it is often
difficult to achieve a highly uniform and well-defined
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Polvm. Sci. Polym. Lett. Ed., 19, 229 (1981) and J. Chem. Soc.
Faraday Trans. 1, 78, 2497 (1982)).
In the radical copolymerization of isobutylene (IB) and
acrylic esters, the resulting copolymers contain at most 20-
30% of IB and have low molecular weights because of
degradative chain transfer of IB (U.S. Pat. 21os. 2,411,599 and
2,531,196; and Mashita et al, Polymer, 36, 2973 (1995).
Conjugated monomers such acrylic esters and acrylonitrile
react :;ith donor monomers such as propylene, isobutylene,
styrene in the presence of alkylaluminum halide to give 1:1
alternating copolymers (Hirooka et al, J. Polym. Sci. Polym.
Chem., 11, 1281 (1973)). The alternating copolymer was
obtained when [Lewis acid]o/(acrylic esters)p = 0.9 and (IB)o >
[acrylic esters]o. The copolymer of IB and methyl acrylate
(MA) obtained by using ethyl aluminum sesquichloride and 2-
methyl pentanoyl peroxide as an initiating system is highly
alternating, with either low (Kuntz et al, J. Polym. Sci.
Polym. Chem., 16, 1747 (1978)) or high (60%) isotacticity in
the presence of EtAlCl2 (10 molar% relative to MA) at 50 C
(FlorianczVk et al, Makromol. Chem., 183, 1081 (1982)).
Recently, alkyl boron halide was found to have a much
higher activity than alkyl aluminum halide in alternating
copolymerization of IB and acrylic esters (Mashita et al,
Polymer, 36, 2983 (1995)). The polymerization rate has a
maximum at about -50 C and decreased significantly above 0
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C. The copoly:nerization is controlled by O, in terms of both
rate and molecular weight. The alternating copolymer was
obtained when [IB]o > [Acrylic estersjo. Stereoregularity was
considered to be nearly random. The copolymer is an elastomer
of high tensile strength and high thermal decomposition
temperature. The oil resistance is very good, especially at
elevated temperatures, and the hydrolysis resistance was
excellent compared to that of the corresoonding poly(acrylic
ester)s (Mashita et al, supra).
Dendrimers have recently received much attention as
materials with novel physical properties (D. A. Tomalia, A. M.
Naylor, W. A. G. III, Angew. Chem., Int. Ed. Eng1. 29, 138
(1990); J. M. J. Frechet, Science 263, 1710 (1994)). These
polymers have viscosities lower than linear analogs of similar
molecular weight, and the resulting macromolecules can be
highly functionalized. However, the svnthesis of dendrimers
is not trivial and requires multiple steps, thus generally
precluding their commercial development.
Polymers consisting of hyperbranched phenylenes (0. W.
Webster, Y. H. Kim, J. Am. Chem. Soc. 112, 4592 (1990) and
Macromolecules 25, 5561 (1992)), aromatic esters (J. M. J.
Frechet, C. J. Hawker, R. Lee, J. Am. Chem. Soc., 113, 4583
(1991)), aliphatic esters (A. Hult, E. Malmstrom, M.
Johansson, J. Polym. Sci. Polym. Ed. 31, 619 (1993)),
siloxanes (L. J. Mathias, T. W. Carothers, J. Am. Chem. Soc.
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113, 4043 (1991) ), amines (M. Suzuki, :.. Li, T. Saegusa,
PlacromoZecules 25, 7071 (1992)) and liauid crystals (V.
Percec, M. Kawasumi, Macromolecules 25, 3843 (1992) ) have been
synthesized in the past few years.
Recently, a method has been described by which
functionaiized vinyl monomers could be used as monomers for
the synthesis of hyperbranched polymers by a cationic
polymerization (J. 14. j. Frechet, et al., Science 269, 1080
(1995)). The monomer satisfies the ::B, requirements for
formation of hyperbranched polymers by the vinyl group acting
as the difunctional B group, and an additional alkyl halide
functional group as the A group. By activation of the A group
with a Lewis acid, polymerization through the double bond can
occur. In this method, 3-(1-chloroethyl)-ethenylbenzene was
used as a monomer and was cationically polymerized in the
presence of SnClq .
A need is strongly felt for a radical polymerization
process which provides (co)polyTners having a predictable
molecular weight and a controlled molecular weight
distribution ("polydispersity"). A further need is strongly
felt for a radical polymerization process which is
sufficiently flexible to provide a wide variety of products,
but which can be controlled to the degree necessary to provide
highly uniform products with a controlled structure (i.e.,
controllable topology, composition, stereoregularity, etc.),
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many of which are suitable for highly specialized uses (such
as thermoplastic elastomers, end-functional polymers for
chain-extended polyurethanes, polyesters and polyamides,
dispersants for polymer blends, etc.).
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to
provide a controlled free radical polymerization process,
of atom or group transfer radical polymerization,
comprising the steps of:
radically polymerizing one or more radically
(co)polymerizable monomers in the presence of a system
comprising:
an initiator having one or more radically
transferable atoms or groups,
a transition metal compound which participates in
a reversible redox cycle with said initiator or a
dormant polymer chain end, and in its redox
conjugate form with a growing polymer chain end
radical,
an amount of the redox conjugate of the
transition metal compound sufficient to
deactivate at least some initially-formed
radicals, wherein the transition metal compound
and the redox conjugate are present in amounts
providing a transition metal compound:redox
conjugate molar ratio of from 99.9:0.1 to
0.1:99.9, and any N-, 0-, P- or S- containing
ligand which coordinates in a 6-bond to the
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transition metal, any carbon-containing ligand
which coordinates in a7E-bond to the transition
metal or any carbon-containing ligand which
coordinates in a carbon-transition metal a-bond
but which does not form a carbon-carbon bond with
said monomer under the polymerizing conditions.
A further object of the present invention is an
initiating system comprising:
an initiator having a radically transferable atom
or group,
a transition metal compound which participates in
a reversible redox cycle,
an amount of the redox conjugate of the
transition metal compound sufficient to deactivate at least
some radicals formed during a reaction between said
initiator, said transition metal compound and radically
polymerizable monomer, and
any N-, 0-, P- or S- containing ligand which
coordinates in a a-bond to the transition metal, any
carbon-containing ligand which coordinates in a7i-bond to
the transition metal of any carbon-containing ligand which
coordinates in a carbon-transition metal a-bond ligand
which does not form a carbon-carbon bond with a radically
polymerizable monomer under conditions which controllably
polymerize said monomer.
A further object of the present invention is to
provide a novel method for radical polymerization of
alkenes based on atom transfer radical polymerization
(ATRP), which provides a level of molecular control over
the polymerization process presently obtainable only by
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living ionic or metathesis polymerization, and which leads
to more uniform and more highly controllable products.
A further object of the present invention is to provide
novel improvements to a method for radical polymerization of
alkenes based on atom transfer radical polymerization (ATRP),
which increases initiator efficiencies and process yields, and
improves product properties.
A further object of the present invention is to provide a
broad variety of novel (co)polymers having more uniform
properties than those obtained py conventional radical
polymerization.
A further object of the present invention is to provide
novel (co)polymers having new and useful structures and
properties.
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A further object of the present invention is to provide a
process for radically polymerizing a monomer which is
adaptable to use with existing equipme t.
A further object of the present invention is to provide a
method for producing a (co)polymer which relies on readily
available starting materials and catalysts.
A further object of the present invention is to provide
(co)polymers having a wide variety of compositions (e.g.,
random, alternating, tapered, end-functional, telechelic,
etc.) and topologies (block, graft, star, dendritic or
hyperbranched, comb, etc.) having controlled, uniform and/or
well-defined structures and properties.
A further object of the present invention is to provide a
novel method for radically polymerizing a monomer which can
use water as a solvent and which provides novel water-soluble
(co)polymers.
A further object of the present invention is to provide
novel (co)polymers which are useful as gels and hydrogels, and
to provide novel methods for making such (co)polymers.
A further object of the present invention is to provide
novel (co)polymers which are useful in a wide variety of
applications (for example, as adhesives, asphalt modifiers, in
contact lenses, as detergents, diagnostic agents and supports
therefor, dispersants, emulsifiers, elastomers, engineering
resins, viscosity index improvers, in ink and imaging
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compositions, as leather and cement modifiers, lubricants
and/or surfactants, with paints and coatings, as paper
additives and coating agents, as an intermediate for preparing
larger macromolecules such as polyurethanes, as resin
modifiers, in textiles, as water treatment chemicals, in the
chemical and chemical waste processing, composite fabrication,
cosmetics, hair products, personal care products in plastics
compounding as, for example, an antistatic agent, in food and
beverage packaging, pharmaceuticals [as, e.g., a bulking
agent, "slow release" or sustained release compounding agent],
in rubber, and as a preservative).
These and other objects of the present invention, which
will be readily understood in the context of the following
detailed description of the preferred embodiments, have been
provided in part by a novel controlled process of atom (or
group) radical transfer polymerization, comprising the steps
of:
polymerizing one or more radically polymerizable monomers
in the presence of an initiating system comprising:
an initiator having a radically transferable atom or
group,
a transition metal compound which participates in a
reversible redox cycle (i.e., with the initiator),
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an amount of the redox-conjugate of the transition
metal compound sufficient to deactivate at least some
initially-formed radicals, and
any 11-, 0-. P- or S- containing ligand which
coordinates in a a-bond or any carbon-containing ligand
which coordinates in a 7t-bond to the transition metal, or
any carbon-containing ligand which coordinates in a
carbon-transition metal a-bond but which does not form a
carbon-carbon bond with said monomer under the
polymerizing conditions,
to form a (co)polymer, and
isolating the Formed (co)polymer;
and, in part, by novel (co)polymers prepared by atom (or
group) radical transfer polymerization.
BRIEF DESCRIPTION OF THE FIGURES
Figure 1 shows a varietv of different polymer topologies,
compositions and functionalizations :Yhich can be achieved by
the present invention, but to which the present invention is
not restricted;
Figure 2 shows a comparison of mechanisms, exemplary
kinetic parameters and product properties of conventional
radical polymerization with the present "living"/controlled
radical polymerization;
Figures 3A-B are plots of molecular weight (M,) and
polydispersities (14,/Mõ) vs. conversion % (Fig. 3A) and of the
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instantaneous composition of the copolymer (:'ln,t) vs. chain
length (Fig. 3B) for the gradient copolymerization of Example
16 below;
Figures 4A-B are plots of molecular weight (?=1õ) and
polydispersities (1,1,/1=17) vs. conversion $(Fig. 4A) and of the
instantaneous composition of the copolymer (Fl,,s,) vs. chain
length (Fia. 4B) for the gradient copolymerization of Example
17 below;
Figures 5A-B are plots of molecular weiaht (M;,) and
polydispersities vs. time (Fig. 5A) and of the
instantaneous composition of the copolymer (Flns, ) vs. chain
length (Fig. 5B) for the gradient coro)ymerization of Example
18 below;
Figures 6A-B are plots of molecular weight (11_,) and
polydispersities (r=i.,/I=i,,) vs. time (Fig. 6A) and of the
instantaneous composition of the copolymer (FiRS,) vs. chain
length (Fig. 6B) for the gradient copolymerization of Example
19 below;
Figures 7A-B are plots of molecular weight (M,,) and
polydispersities (24,,,/11.) vs. time (Fig. 7A) and of the
instantaneous composition of the copolymer (FiõB,) vs. chain
length (Fig. 7B) for a gradient copolymerization described in
Example 20 below;
Figures 8A-B are plots of molecular weight (M.t,) and
polydispersities (M1/NL ) vs. time (Fig. BA) and of the
instantaneous composition of the copolymer (Firõ,) vs. chain
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length (Fig. 83) ;:or a gradient copolyme.rization described in
Example 20 below; and
Figures 9A-B are plots of molecular weight (21T ) and
polydispersities vs. time (Fig. 9A) and of the
instantaneous composition of the copolymer (FinSL) vs. chain
length (Fig. 9B) for a gradient copolymerization described in
Exainple 20 below.
Figure 10 is a plot of the fraction of monomer A in
copolymer and the fraction of monomer B in copolymer vs.
chain length for gradiant copolymers.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
It has been conceptualized that if (1) the organic halide
R-M,-;, resulting from an ATRA reaction is sufficiently reactive
towards the transition metal 2=St" and (2) the alkene monomer is
in excess, a number or sequence of atom transfer radical
additions (i.e., a possible "living"/ controlled radical
polymerization) may occur. By analogy to ATRA, the present
new process of radical polymerization has been termed "atom
(or group) transfer radical polvmerization" (or "ATRP"), which
describes the involvement of (1) the atom or group transfer
pathway and (2) a radical intermediate.
Living/controlled polymerization (i.e., when chain
breaking reactions such as transfer and termination are
substantially absent) enables control of various parameters of
macromolecular structure such as molecular weight, molecular
weight distribution and terminal functionalities. It also
allows the preparation of various copolymers, including block
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and star copolymers. Living/controlled radical polymerization
requires a low stationary concentration of radicals, in
equilibriv.m with various dormant species.
In the context of the present invention, the term
"controlled" refers to the ability to produce a product having
one or more properties which are reasonably close to their
predicted value (presuming a particular initiator efficiency).
For example, if one assumes 100% initiator efficiency, the
molar ratio of catalvst to monomer leads to a particular
predicted molecular weight. The polymerization is said to be
"controlled" if the resulting number average molecular weight
(M,,(act)) is reasonably close to the predicted number average
molecular weight (14,,,(pred)); e.g., within an order of
magnitude, preferably within a factor of four, more preferably
within a factor of three and most preferably within a factor
of two (i.e., M.,(act) is in the range of from (0.1) x 11,(pred)
to 10 x t=iõ(pred), preferably from (0.25) :: t=%(pred) to 4 x
Mõ(pred) , more preferably from (0.5) x tdõ(pred) to 2 2% (pred)
and most preferably from ( 0. 8) x ri, (pred) to 1. 2 x ri, (pred) ).
similarly, one can "control" the polydispersity by
ensuring that the rate of deactivation is the same or greater
than the initial rate of propagation. However, the importance
of the relative deactivation/propagation rates decreases
proportionally with increasing polymer chain length and/or
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increasing predicted molecular weight or degree of
polymerization.
The present invention describes use of novel initiating
systems leading to living/controlled radical polymerization.
The initiation system is based on the reversible formation of
growing radicals in a redox reaction between various
transition metal comaounds and an initiator, exemplified by
(but not limited to) alkyl halides, aralkyl halides or
haloalkyl esters. Using 1-phenvlethyl chloride (1-PEC1) as a
model initiator, CuCl as a model catalyst and bipyridine (Bpy)
as a model ligand, a "living" radical bulk polvmerization of
styrene at 130 C affords the predicted molecular weight up to
Mt, = 105 with a narrow molecular weight distribution (e.g.,
I,,/Mn < 1. 5 ) .
A key factor in the present invention is to achieve rapid
exchange between growing radicals present at low stationary
concentrations (in the range of from 10' mol/L to 10"' mol/L,
preferably 10'B mol/L to 10'S mol/L) and dormant chains present
at higher concentrations (typically in the range 10-' mol/L to
3 mol/L, preferably 10'2 mol/L to 10' mol/L) . It may be
desirable to "match" the initiator/ catalyst/ ligand system and
monomer(s) such that these concentration ranges are achieved.
Although these concentration ranges are not essential to
conducting polymerization, certain disadvantageous effects may
result if the concentration ranges are exceeded. For example,
-2i-
CA 02585469 2007-05-03
if the concentration of growing radicals exceeds 10-' mol/L,
there may be too many active species in the reaction, which
may lead to an undesirable increase in the rate of side
reactions (e.g., radical-radical quenching, radical
abstraction from species other than the catalyst system,
etc.). If the concentration of growing radicals is less than
10'9 mol/L, the rate may be undesirably slow. However, these
considerations are based on an assumption that onlv free
radicals are present _n the reaction system. It is believed
that some radicals are in a caged form, the reacti=iities of
which, especially in termination-deactivation reactions, may
differ from those of uncaged free radicals.
Similarly, if the concentration of dormant chains is less
than 10'' mol/L, the molecular weight of the product polymer
may increase dramatically, thus leading to a potential loss of
control of the molecular weight and the polydispersity of the
product. On the other ftand, if the concentration of dormant
species is greater than 3 mol/L, the molecular weight of the
product may become too small, and the properties of the
product may more closely resemble the properties of oligomers.
(However, oligomeric products are useful, and are intended to
be included within the scope of the invention.)
For example, in bulk, a concentration of dormant chains
of about 10"2 mol/L provides product having a molecular weight
of about 100,000 g/mol. on the other hand, a concentration of
- 22 -
CA 02585469 2007-05-03
dormant chains exceeding 1 M leads to formation of
(roughly) less than decameric products, and a concentration
of about 3 M leads to formation of (predominantly) trimers.
US patent no. 5,763,548 discloses a method of
preparing a (co)polymer by ATRP which comprises:
polymerizing one or more radically polymerizable
monomers in the presence of an initiator having a radically
transferable atom or group, a transition metal compound and a
ligand to form a (co)polymer, the transition metal compound
being capabie of participating in a redox cycle with the
initiator and a dormant polymer chain, and the ligand being
any N-, o-, P- or S- containing compound which can coordinate
in a a-bond to the transition metal or any carbon-containing
compound which can coordinate in a rr-bond to the transition
metal, such that direct bonds between the transition metal and
growing polymer radicals are not formed, and
isolating the formed (co)polymer.
The present invention includes the following:
(1) an ATRP process in which the improvement comprises
polymerizing in the presence of an amount of the
corresponding reduced or oxidized transition metal
compound which deactivates at least some free
radicals;
23
CA 02585469 2007-05-03
(2) an ATRP process in which the improvement comprises
polymerizing in a homogeneous system or in the
presence of a solubilized initiating/catalytic
system;
(3) end-functional, site-specific functional and
telechelic homopolymers and copolymers (see Fig. 1);
(4) block, random, graft, alternating and tapered (or
"gradient") copolymers which may have certain
properties or a certain structure (e.g. , a copolymer
of alternating donor and acceptor monomers, such as
the radical copolymer of isobutylene and a
(meth)acrylate ester; see Fig. 1);
(5) star, comb and dendritic (or "hyperbranched")
polymers and copolymers (see Fig. 1);
(6) end-functional and/or multi-functional hyperbranched
polymers (see Fig. 1);
(7) cross-linked polymers and gels;
(8) water-soluble polymers and new hydrogels (e.g.,
copolymers prepared by radical polymerization,
comprising a water-soluble backbone and well-defined
hydrophobic (co) polymer chains grafted thereonto);
and
(9) an ATRP process using water as a medium.
In one embodiment, the present invention concerns
improved methods of atom or group transfer radical
- 24 -
CA 02585469 2007-05-03
poly:nerization, in which a proportion (e.g., 0.1-99.9 molo,
preferably 0.2-10 molo and more preferably 0.5-5 mol%) of the
transition metal catalyst is in an oxidized or reduced state,
relative to the bulk of the transition metal catalyst. The
oxidized or reduced transition metal catalyst is the redox
conjugate of the primary transition metal catalyst; i.e., for
the M~"' :M_m' redox cycle, 90-99. 9 mol% of transition metal t=it
atoms may be in the n' oxidation state and 0.1-10 molo of
transition metal t=i, atoms may be in the m' oxidation state.
The term "redox conjugate" thus refers to the corresponding
oxidized cr reduced form of the transition metal catalyst.
Oxidation states n and m are attained by transition metal M_ as
a consequence of conducting ATRP.
The present Inventors have found that an amount of redox
conjugate sufficient to deactivate at least somelof the
radicals which may form at the beginning of polyznerization
(e.g., the product of self-initiation or of addition of an
initiator radical or growing polymer chain radical to a
monomer) greatly improves the polydispersity and control of
the molecular weight of the product. The effects and
importance of rates of exchange between growing species of
different reactivities and different lifetimes, relative to
the rate of propagation, has not been sufficiently explored in
previous work by others, but has been found by the present
Inventors to have a tremendous effect on polydispersity and
- 25 -
CA 02585469 2007-05-03
control of molecular weight in living/controlled
polymerizations.
As is shown in Figure 2, both conventional and controlled
polymerizations comprise the reactions of initiating radicals
with monomer at a rate constant k;, propagation of growing
chains with monomer at a rate constant }:r, and termination by
coupling and/or disproportionation with an average rate
constant }:_. In both systems, the concentration of radicals at
any given moment (the momentary concentration of arowing
radicals, or [P']o) is relatively low, about l0-' mol/L or less.
However, in conventional radical polymerization,
initiator is consumed very slowly (kd., z 10-5 = 1 s_1)
Furthermore, 4-n conventional radical polymerization, the
initiator half-lifetime is generally in the range of hours,
meaning that a significant proportion of initiator remains
unreacted, even after monomer is completely consumed.
By ccntrast, in controlled polymerization svstems, the
initiator is largely consumed at low monomer conversion (e.g.,
90% or more of initiator may be consumed at less than 10%
monomer conversion).
In ATRP, growing radicals are in dynamic equilibrium with
dormant covalent species. Covalent R-X and P-X bonds
(initiator and dormant polymer, respectively) are
homolytically cleaved to form initiating (R') or propagating
(P') radicals and corresponding counter-radicals X. The
- 26 -
CA 02585469 2007-05-03
eauilibrium position defines the momentary concentration of
growing radicals, the polymerization rate and the contribution
of termination. The dynamics of equilibration also affects
polydispersity and the molecular weight of the polymer as a
function of monomer conversion.
A model study has been performed on polymerization of
methyl acrylate at 100 C, based on numerical integration using
a discrete Galerkin method (Predici program). In this study,
the rate constants of propagation (kp = 7 x 10' mol" L s-') and
termination (kt = 10' mol-' L s-') were based on data available
from published literature. The rate constants of activation
and deactivation for the initiating system 1-phenylethyl
chloride/CuCl/2,2'-bipyridyl were then varied over five orders
of magnitude, maintaining an equilibrium constant value K
10'8. As a result of this model study, it was found that
addition of 1% Cu(II) (redox conjugate) dramatically improves
the polydispersity of, and provides predictable molecular
weights for, the obtained (co)polymer products.
The equilibrium constant (i.e., the ratio of the
activation rate constant k, to deactivation rate constant kd)
can be estimated from known concentrations of radicals,
covalent alkyl halides, activator and deactivator according to
the equation:
K = k,/kd =( [Cu12][P'])/( [Cui) [I3o)
- 27 -
CA 02585469 2007-05-03
Simulations were performed for bulk polymerization of
methyl acrylate ([M]o = 11 2=1) or styrene ([14]o = 9 M) using an
initiatina system containing 1-PEC1 (~IJo = 0.1 M), a 2,2'-
bipyridyl)CuCl complex ([Cui], = 0.1 M) and either 1% or 0% CuIl
as an initial deactivator ([ CuII ] o = 0. 001 2=1 or 0 M) . The
stationary concentration of radicals is approximately 10'' M,
leading to the result that K is approximately 10'8.
After initiation in the system without Cu(II), the
momentary concentration of radicals is reduced from 8 x 10'' M
at 10% conversion to 3. 3 x 10-' t=i at 50% conversion and 1. 6 x
10'' Pd at 90% conversion. At the same time, the concentration
of deactivator (CuII) increases from 1.2 x 10'4 M at 10 o
conversion to 3 x 10-1 t=I at 50% conversion and 6 x 10'4 M at 90%
conversion. The concentration of deactivator corresponds to
the concentration of terminated chains, which at 90% monomer
conversion, -;s only about 0.6% of all chains generated from
the initiator.
In the presence of 1% deactivator (redox conjugate), a
nearly constant concentration of growing radicals is
predicted. The momentary concentration of polymer radicals is
much more constant in the presence of 1% deactivator, going
from 0.98 x 10'' M at 10% conversion to 0.94 x 10" M at 50%
conversion and 0.86 x 10'' M at 90% conversion. At the same
time, the deactivator concentration increases from 1.01 x 10''
M at 10% conversion to 1.05 x 10'3 M at 50% conversion and 1.15
- 28 -
CA 02585469 2007-05-03
x 10-' 14 at 90% conversion. The concentration of terminated
chains corresponds to the increase in concentration of
deactivator although the initial concentration, which
translates to 0.15% of ail chains being terminated at 90%
conversion.
The dynamics of exchange has no effect on kinetics in the
studied range of ka and k,, values. However, dynamics has a
tremendous effect on molecular weights and polydispersities.
In the absence ef deactivator in the model svstems
studied, a degree of polymerization (DPn) of about 90 is
expected. However, if deactivation is slow, very high
molecular weights are initially observed. As conversion
increases, the molecular weights slowly begin to coincide with
predicted values. The initial discrepancy has a tremendous
effect on polydispersities, as will be discussed below.
If deactivation is sufficiently fast (in the model
system, about 10' mol-' L s-=) , the predicted and observed
molecular weights are in substantial agreement from the
beginning of polymerization. However, when deactivation is
slow, the initial DP is substantially higher than predicted
(DP = 60 when kd = 106 2.1'1 s-l, and DP = 630 when k. = lOs 14'1
s'1). Thus, initial values of DP can be predicted by the ratio
of propagation to deactivation rates by the equation:
DP = Rp/Rd = kp[M}o[P']/ka[CuI13o[P*3
- 29 -
CA 02585469 2007-05-03
Regardless of the rate of deactivation, however, initial
polydispersities are much higher than those predicted for a
Poisson distribution. However, if deactivation is
sufficiently fast, at complete conversion, vary narrow
polydispersities (t~/M.) are observed (e.g., less than 1.1).
On the other hand, if the rate of deactivation is about the
same as the rate of termination (in the model case, about 10'
t=i"' s-1), then the polvdispersity at complete conversion is
about 1.5. When deactivation is about three times slower, the
polydispersity at complete conversion is about -7.5.
However, in the presence of 1% deactivator, a
deactivation rate which is about the same as the termination
rate results in a polydispersity close to ideal (< 1.1) at
complete conversion, although initially, it is rather high
(about 2), decreasing to about 1.5 at 25% conversion and < 1.2
at 75% conversion. Where deactivation is slower (k,, = 106),
the final polydispersity is 1.7. A small quantity of
deactivator (redox conjugate) is sufficient to trap or quench
the free radicals formed during polymerization. A large
excess of redox conjugate is not necessary, although it does
not have an adverse or continuous effect on the polymerization
rate.
It is noted that an average termination rate constant k. _
10' M-' s-1 was used. However, the actual termination rate
constant strongly depends on chain length. For monomeric
- 30 -
CA 02585469 2007-05-03
radicals, it can be as high at 105 M- s-l, but for very long
chains, it can be as low as 102 M-1 s-'. One major difference
between controlled polymerization and conventional radical
polymerization is that nearly all chains have similar chain
length in controlled polymerization, whereas new radicals are
continuously generated in conventional radical polymerization.
Therefore, at substantial conversion, long chain radicals do
not react with one another, but rather, with newly generated
low molecular mass radicals in conventional polymerization.
In controlled systems, by contrast, after a certain chain
length has been achieved, the reaction mixture becomes more
viscous, and the actual rate constant of termination may
dramatically drop, thus improving control of polymerization to
a degree greater than one would predict prior to the present
invention.
The addition of a redox conjugate to ATRP also increases
control of molecular weight and polydispersities by scavenging
radicals formed by other processes, such as thermal self-
initiation of monomer. For example, in the model systems
studied, CuCl: acts as an inhibitor of polymerization, and
scavenges polymer chains at an early stage, preventing
formation of a high molecular weight polymer which may be
formed by thermal self-initiation.
It has been observed by the present Inventors that the
rate of polymerization is not affected in a linear fashion by
- 31 -
CA 02585469 2007-05-03
the amount or concentration of the deactivating agent (redox
conjugate). For example, the presence of -5 molo of redox
conjugate may be expected to decrease the polymerization rate
10-fold relative to 0.5 molo of redox conjugate. However, 5
mol% of redox conjugate actually decreases the polymerization
rate by a significantly smaller amount than 10-fold relative
to 0.5 molo of redox conjugate. Although a precise
explanation for this phenomenon is not vet available, it is
believed that many radicals generated by the present hTRP
initiator/transition metal compound/ligand system may be
protected by a solvent/monomer "cage." Thus, the presence of
more than 10 molo of redox conjugate does not adversely affect
polymerization by ATRP, although it may slow the
polymerization rate to a small extent.
Experimental observations also support the idea that
large amounts of redox conjugate are not harmful to
polymerization, a result which is surprising in view of
observations that redox conjugates adversely affect ATRA. For
example, in the heterogeneous ATRP of acrylates using
copper(I) chloride, the color of the catalyst changes from red
(Cu') to green (Cuii). However, the apparent rate constant of
polymerization is essentially constant, or at least does not
significantly decrease.
As described above, the redox conjugate is present in an
amount sufficient to deactivate at least some of the
- 32 -
CA 02585469 2007-05-03
initially-formed initiator-monomer adduct radicals, thermal
self-initiation radicals and subsequently-formed arowing
polymer radicals. One key to achieving narrow
polydispersities is to control the polymerization reaction
parameters such that the rate of radical deactivation is
roughly the same as or greater than the rate of propagation.
In one embodiment, the improvement to the method
comprises adding the transition metal redox conjugate to the
reaction mixture prior to polymerizing. Alternatively, when
the transition metal compound is commercially available as a
mixture with its redox conjugate (e.g., many commercially
available Cu(I) salts contain 1-2 mola of Cu(II)), the
improved process comprises adding the transition metal
compound to the polymerization reaction mixture without
purification.
In an alternative embodiment, the improved ATRP method
comprises exposing the transition metal compound to oxygen for
a length of time prior to polymerizing the monomer(s). In
preferred embodiments, the source of oxygen is air, and the
length of time is sufficient to provide from 0.1 to 10 molo of
the redox conjugate of the transition metal compound. This
embodiment is particularly suitable when the transition metal
is a Cu(I) compound, such as CuCl or CuBr.
One may also conduct a"reverse" ATRP, in which the
transition metal compound is in its oxidized state, and the
- 33 -
CA 02585469 2007-05-03
polvmerization is initiated by, for example, a radical
initiator such as azobis(isobutyronitrile) ("AIBN"), a
peroxide such as benzovl peroxide (BPO) or a peroxy acid such
as peroxyacetic acid or peroxybenzoic acid. The radical
initiator is believed to initiate "reverse" ATRP in the
following fashion:
I-I > 2 I'
I ?=1."*'X I-X I1_"Y."
I' + M I-M
I-M- + M t".1Xr, I-M-X + i=1L"X.,.
I-M' - n M > I-1~i1
I-Mr,., + M.-x, -= I-M,.~-X +
where ":" is the initiator, M"X"_1 is the transition metal
comoound, i=1 is the monomer, and I-M-X and participate in
"conventional" or "forward" ATRP in the manner described
above.
After the polymerizing step is complete, the formed
polymer is isolated. The isolating step of the present
process is conducted by known procedures, and may comprise
evaporating any residual monomer and/or solvent, precipitating
in a suitable solvent, filtering or centrifuging the
precipitated polymer, washing the polymer and drying the
washed polymer. Transition metal compounds may be removed by
- 34 -
CA 02585469 2007-05-03
passing a mixture containing them through a column or pad of
alumina, silica and/or clay. Alternatively, transition metal
compounds may be oxidized (if necessary) and retained in the
(co)polymer as a stabilizer.
Precipitation can be typically conducted using a suitable
CS-Ce-alkane or CS-Co-cycloalkane solvent, such as pentane,
hexane, heptane, cyclohexane or mineral spirits, or using a C:-
C6-alcohol, such as methanol, ethanol or isopropanol, or any
mixture of suitable solvents. Preferably, the solvent for
precipitating is water, hexane, mixtures of hexanes, or
methanol.
The precipitated (co)polymer can be filtered by gravity
or by vacuum filtration, in accordance with known methods
(e.g., using a Buchner funnel and an aspirator).
Alternatively, the precipitated (co)polymer can be
centrifuged, and the supernatant liquid decanted to isolate
the (co)polymer. The (co)polymer can then be can be washed
with the solvent used to precipitate the polymer, if desired.
The steps of precipitating and/or centrifuging, filtering and
washing may be repeated, as desired.
Once isolated, the (co)polymer may be dried by drawing
air through the (co)polymer, by vacuum, etc., in accordance
with known methods (preferably by vacuum). The present
(co)polymer may be analyzed and/or characterized by size
- 35 -
CA 02585469 2007-05-03
exclusion chromatography, NMR spectroscopy, etc. , in
accordance with known procedures.
The various initiating systems of the present invention
work for any radically polymerizable alkene, including
(meth) acrylates, styrenes and dienes. It also provides
various controlled copolymers, including block, random,
alternating, gradient, star, araft or "comb," and
hyperbranched and/or dendritic (co)polvmers. (In the present
application, "(co)polymer" refers to a homopolvmer, comolymer,
or mixture thereof.) Similar systems have been used
previously in organic synthesis, but have not been used for
the preparation of well-defined macromolecular compounds.
In the present invention, any radically polymerizable
alkene can serve as a monomer for polymerization. However,
monomers suitable for polymerization in the present method
include those of the formula:
R' R'
\ /
C=C
/ \
R2 R'
wherein R' and R2 are independently selected from the group
consisting of H, halogen, CN, straight or branched alkyl of
from 1 to 20 carbon atoms (preferably from 1 to 6 carbon
atoms, more preferably from 1 to 4 carbon atoms) which may be
substituted with from 1 to (2n+l) halogen atoms where n is the
- 36 -
CA 02585469 2007-05-03
number of carbon atoms of the al}:yl group ( e. g. CF3) ~3-
unsaturated straight or branched alkenyl or al}:ynyl of 2 to 10
carbon atoms (preferably from 2 to 6 carbon atoms, more
preferably from 2 to 4 carbon atoms) which may be substituted
with from 1 to (2n-1) halogen atoms (preferably chlorine)
where n is the number of carbon atoms of the alkyl group (e.g.
CH,=CC1-), C,-C, cycloalkyl which mav be substituted with from
1 to (2n-1) halogen atoms (preferably chlorine) where n is the
number of carbon atoms of the cycloal}:yl group, C(=Y)R5,
C ( =Y ) NR'R' , YC ( =Y ) RS , SOR5, SO,RS , OSO~R', PdReSO,R' , PRS, P ( =Y
) R52 ,
YPR', , YP (=Y ) RS: , NRe: which may be quaternized with an
additional Re group, aryl and heterocyclyl; where Y may be NR8,
S or 0 (preferably 0); R' is alkyl of from 1 to 20 carbon
atoms, alkylthio of from 1 to 20 carbon atoms, OR2" (where R2'
is H or an alkali metal), alkoxy of from 1 to 20 carbon atoms,
aryl, aralkyl, heterocyclyl, aryloxy or heterocyclyloxy; R6
and R7 are independently are independently H or alkyl of
from 1 to 20 carbon atoms, or R6 and R7 may be joined
together to form an alkylene group of from 2 to 7
(preferably 2 to 5) carbon atoms, thus forming a 3- to 8-
membered (preferably 3- to 6-membered) ring, and R8 is H,
straight or branched Cl-C20 alkyl or aryl;
R' and R4 are independently selected from the group
consisting of H, halogen (preferably fluorine or chlorine), C1-
C6 (preferablv C,) alkyl and COOR9 (where R9 is H, an alkali
JO
metal, or a C,-C6 alkyl group), or
37
CA 02585469 2007-05-03
R1 and R' may be ;oined to form a group of the formula
(CH2),,. (which may be substituted with from 1 to 2n' halogen
atoms or C.-C; alkyl groups) or C(=0)-Y-C(=O), where n' is from
2 to 6(preferablv 3 or 4) and Y is as defined above; and
at least two of R1, R', R3 and R are H or halogen.
In the context of the present application, the terms
"alkyl", "alkenyl" and "alkynyl" refer to straight-chain or
branched groups (except for C. and C. groups). "Alkenyl" and
"alkynvl" groups mav have sites of unsaturation at anv
adjacent carbon atom position(s) as long as the carbon atoms
remain tetravalent, but a,G- or terminal (i.e., at the w- and
(w-1)-positions) are preferred.
Furthermore, in the present application, "aryl" refers to
phenyl, naphthyl, phenanthryl, phenalenyl, anthracenyl,
triphenylenyl, fluoranthenyl, pyrenyl, pentacenyl, chrysenyl,
naphthacenyl, hexaphenyl, picenyl and perylenyl (preferably
phenyl and naphthyl) in which each hydrogen atom may be
replaced with halogen, alkyl of from 1 to 20 carbon atoms
(preferably from 1 to 6 carbon atoms and more preferably
methyl) in which each of the hydrogen atoms may be
independently replaced by an X group as defined above (e.g., a
halide, preferably a chloride or a bromide), alkenyl or
alkynyl of from 2 to 20 carbon atoms in which each of the
hydrogen atoms may be independently replaced by an X group as
defined above (e.g., a halide, preferably a chloride or a
- 38 -
CA 02585469 2007-05-03
bromide), alkoxy of from 1 to 6 carbon atoms, alkylthio of
from 1 to 6 carbon atoms, C,-C9 cycloalkyl in which each of the
hydrogen atoms may be independently replaced by an X group as
defined above (e.g., a halide, preferably a chloride or a
bromide), phenyl, NH, or C,-C6-alkylamino or C,-CS-dialkylamino
which may be quaternized with an R group, COR', OC(=O)R5, SOR5,
SO,R5, OSO,RS, PR52, PORS: and phenyl which may be substituted
with from 1 to 5 halogen atoms and/or C:-C, alkyl groups.
(This definition of "aryl" also applies to the aryl groups in
"aryloxy" and "aralkyl.") Thus, phenvl may be substituted
from 1 to 5 times and naphthyl may be substituted from 1 to 7
times (preferably, any aryl group, if substituted, is
substituted from 1 to 3 times) with one or more of the above
substituents. More preferably, "aryl" refers to phenyl,
naphthyl, phenyl substituted from 1 to 5 times with fluorine
or chlorine, and phenyl substituted from 1 to 3 times with a
substituent selected from the group consisting of alkyl of
from 1 to 6 carbon atoms, alkoxy of from 1 to 4 carbon atoms
and phenyl. Most preferably, "aryl" refers to phenyl, tolyl,
a-chlorotolyl, a-bromotolyl and methoxyphenyl.
In the context of the present invention, "heterocyclyl"
refers to pyridyl, furyl, pyrrolyl, thienyl, imidazolyl,
pyrazolyl, pyrazinvl, pyrimidinyl, pyridazinyl, pyranyl,
indolyl, isoindolyl, indazolyl, benzofuryl, isobenzofuryl,
benzothienyl, isobenzothienyl, chromenyl, xanthenyl, purinyl,
- 39 -
CA 02585469 2007-05-03
pteridinyl, auinolyl, isoauinolyl, phthalazinyl, quinazolinyl,
quinoxalinyl, naphthyridinyl, phenoxathiinyl, carbazolyl,
cinnolinyl, phenanthridinyl, acridinyl, 1,10-phenanthrolinyl,
phenazinyl, phenoxazinyl, phenothiazinyl, oxazolyl, thiazolyl,
isoxazolyl, isothiazolyl, and hydrogenated forms thereof known
to those in the art. Preferred heterocyclyl groups include
pyridyl, furyl, pyrrolyl, thienyl, imidazolyl, pyrazolyl,
pyrazinyl, pyrimidinyl, pyridazinyl, pyranyl and indolyl, the
most preferred heterocyclyl group being pyridyl. Acccrdingly,
suitable vinyl heterocycles to be used as a monomer in the
present invention include 2-vinyl pyridine, 4-vinyl pyridine,
2-vinyl pyrrole, 3-vinyl pyrrole, 2-vinyl oxazole, 4-vinyl
oxazole, 2-vinyl thiazole, 4-vinyl thiazole, 2-vinyl
imidazole, 4-vinyl imidazole, 3-vinyl pyrazole, 4-vinyl
pyrazole, 3-viilyl pyridazine, 4-vinyl pyridazine, 3-vinyl
isoxazole, 4-vinyl isoxazole, 3-vinyl isothiazole, 4-vinyl
isothiazole, 2-vinyl pyrimidine, 4-vinyl pyrimidine, 5-vinyl
pyrimidine, and 2-vinyl pyrazine, the most preferred being
2-vinyl pyridine. The vinyl heterocycles mentioned above may
bear one or more substituents as defined above for an "aryl"
group (preferably 1 or 2) in which each H atom may be
independently replaced, e.g., with C1-C6 alkyl groups, C1-C6
alkoxy groups, cyano groups, ester groups or halogen atoms,
either on the vinyl group or the heterocyclyl group, but
preferably on the heterocyclyl group. Further, those vinyl
- 40 -
CA 02585469 2007-05-03
heterocycles which, when unsubstituted, contain a II atom may
be quaternized with an R" group (as defined above) , and those
which contain an IJ-H group may be protected at that position
with a conventional blocking or protecting group, such as a
C,-C5 alkyl group, a tris-(C1-C6 alkyl)silyl group, an acyl
group of the formula Ri CO (where R' is aikyi of from 1 to 20
carbon atoms in which each of the hydrogen atoms may be
independently replaced by halide [preferably fluoride or
chloride:), alkenyl of from 2 to 20 carbon atoms (preferably
vinyl), alkynyl of from 2 to 20 carbon atoms (preferably
acetylenvl), phenyl which may be substituted with from 1 to 5
halogen atoms or alkyl groups of from 1 to 4 carbon atoms, or
aralkyl (aryl-substituted alkyl, in which the aryl group is
phenyl or substituted phenyl and the alkyl group is from 1 to
6 carbon atoms, such as benzyl), etc. This definition of
"heterocycl~.~l" also applies to the heterocyclyl groups in
"heterocycl=,ioxy" and "heterocyclic ring."
More specifically, preferred monomers include C,-C:~ a-
olefins, isobutene, (meth)acrylic acid and alkali metal salts
thereof, ,(ineth) acrylate esters of C;-C,0 alcohols,
acrylonitrile, acrylamide, cyanoacrylate esters of C,-C,o
alcohols, didehydromalonate diesters of C1-C6 alcohols, vinyl
pyridines, vinyl td-C.-CS-alkylpyrroles, Id-vinyl pyrrolidones,
vinyl oxazoles, vinyl thiazoles, vinyl pyrimidines, vinyl
imidazoles, vinyl ketones in which the e-carbon atom of the
- 41 -
CA 02585469 2007-05-03
alkvl ;roup does not bear a hydrogen atom (e.g. , vinyl C.-CS-
alkyl ketones in whicZ both a-hydrogens are replaced with C,-C,
alkyl, halogen, etc., or a vinyl phenyl ketone in which the
phenyl may be substituted with from 1 to 5 C.-C<-alkyl groups
and/or halogen atoms) , and styrenes which may bear a C1-CS-
alkyl group on the vinyl nioiety (preferably at the a-carbon
atom) and from 1 to 5(preferably from 1 to 3) substituents on
the phenvl ring selected from the croup consisting of C,-CF-
al}:yl, ._.-C~--alkenv1 (preTerablv : iny1) , C.-C,-ai}:vnvl
(preferably acetylenyl) , C,-C,-alkoxy, halogen, nitro, carboxy,
C1-C5-alkoxycarbonyl, hydroxy protected with a C.-C5 acyl, SO:R5,
cyano and phenyl. The most preferred monomers are isobutene,
N-vinyl pyrrolidone, methyl acrylate (2=SA), methyl methacrylate
(MMA), butyl acrylate (BA), 2-ethylhexyl acrylate (EHA),
acrylonitrile (AN) , styrene (St) and p-tert-butylstyrene.
In the present invention, the _nitiator mav be anv
compound having one cr more atom ks 1 or group ( s.) which are
radically transferable under the polvmerizing conditions.
Suitable initiators include those of the formula:
RiiR12't13C-X
R11C (=O) -:{
R11R'2R'3S i-X
RllRl2N-X
R11PI-X,
- 42 -
CA 02585469 2007-05-03
(R11)nP(Q)m '{?-n
(R110) nP (O) and
(Rii ) (R;2O) P (0) m-X
where:
X is selected from the group consisting of Cl, Br, I, OR10
(as defined above), SR19, SeR14, OC(=0)R'a, OP(=0)R14,
OP(=0) (OR19)21 OP(=0)OR'4, O-N(R14):, S-C(=S)17(P,14);, CN, NC, SCN,
CNS, OCN, CNO and 1+,, where R" is arvl or a straight or
branched C1-C,o (preferably C:-C,o) alkyl group, or where an
N(R")z group is present, the two R' groups may be joined to
form a 5-, 6- or 7-membered heterocyclic ring (in accordance
with the definition of "heterocyclyl" above); and
R11, R" and R" are each independently selected from the
group consisting of H, halogen, C1-C20 alkvl (preferablv C,-C:o
alkyl and more preferably C:-C, alkyl) , C,-Ca cycloalkvl, Ra1Si,
C(=Y) R', C(=Y) NR R' (where R'-R' are as defined above), COC1, OH
(preferably only one of R11, R12 and R" is OH), CN, C,-C.c,
alkenyl or alkynyl (preferably C,-C6 alkenyl or alkynyl, and
more preferably allyl or vinyl), oxiranyl, glycidyl, C2-C6
alkylene or alkenylene substituted with oxiranyl or glycidyl,
aryl, heterocyclyl, aralkyl, aralkenyl (aryl-substituted
alkenyl, where aryl is as defined above, and alkenyl is vinyl
which may be substituted with one or two C,-C6 alkyl groups
and/or halogen atoms [preferably chlorine]), C1-C6 alkyl in
- 43 -
CA 02585469 2007-05-03
which from 1 to all of the hydrogen atoms (preferably 1) are
replaced with halogen (preferably fluorine or chlorine where 1
or more hydrogen atoms are replaced, and preferably fluorine,
chlorine or bromine where 1 hydrogen atom is replaced) and C1-
C6 alkyl substituted with from 1 to 3 substituents (preferably
1) selected from the group consisting of C:-C4 alkoxy, aryl,
heterocyclyl, C(=Y) R5 (where P,5 is as defined above), C(=Y) NR6R'
(where Rh and R7 are as defined above), oxiranyl and glycidyl;
pref erably such that no more than two of R", R" and R13 are H
(more preferably no more than one of R11, R" and R1J is H)
m is 0 or 1; and
n is 0, 1 or 2.
In the present invention, X is preferably Cl or Br. Cl-
containing initiators generally provide (1) a slower reaction
rate and (2) higher product polydispersity than the
corresponding Br-containing initiators. However, Cl-
terminated polymers generally have higher thermal stability
than the corresponding Br-terminated polymers.
When an alkyl, cycloalkyl, or alkyl-substituted aryl
group is selected for one of Rll, Rlz and R1J, the alkyl group
may be further substituted with an X group as defined above.
Thus, it is possible for the initiator to serve as a starting
molecule for branch or star (co)polymers. One example of such
an initiator is a 2,2-bis(halomethyl)-1,3-dihalopropane (e.g.,
2,2-bis(chloromethyl)-1,3-dichloropropane, 2,2-
bis(bromomethyl)-1,3-dibromopropane), and a preferred example
- 44 -
CA 02585469 2007-05-03
is where one of R11, R12 and R1' is phenyl substituted with from
one to five C1-C6 alkyl substituents, each of which may
independently be further substituted with a X group (e.g.,
a,a'-dibromoYylene, tetrakis- or hexakis(a-chloro- or a-
bromomethyl)-benzene).
Preferred initiators include 1-phenylethyl chloride and
1-phenvlethyl bromide (e. g. , where R11 = Ph, R'Z = CHõ R1J = H
and X = Cl or Br), chloroform, carbon tetrachloride, 2-
chloropropionitrile, C.-C,-alkyl esters of a 2-halo-C.-CE-
carboxylic acid (such as 2-chloropropionic acid, 2-
bromopropionic acid, 2-chloroisobutyric acid, 2-
bromoisobutyric acid, etc.), p-halomethylstyrenes and
compounds of the formula C6H,( CH,X ) y or CX,,, [( CHZ )õ( CH.X )]Y. , where
X is Cl or Br, x + y= 6, x' + y' = 4, 0< n'< 5 and both y'
and y> 1. More preferred initiators include 1-phenylethyl
chloride, 1-phenylethyl bromide, methvl 2-chloropropionate,
ethyl 2-chloropropionate, methvl 2-bromopropionate, ethyl 2-
bromoisobutyrate, p-chloromethylstyrene, a,a'-dichloroxylene,
a,a'-dibromoxylene and hexakis (a-bromomethyl) benzene.
Any transition metal compound which can participate in a
redox cycle with the initiator and dormant polymer chain is
suitable for use in the present invention. Preferred
transition metal compounds are those which do not form a
direct carbon-metal bond with the polymer chain. Particularly
suitable transition metal compounds are those of the formula
Nit"'X',,, where:
- 45 -
CA 02585469 2007-05-03
M_"' may be, for example, selected from the group
cons ist ing of Cul' , Cu2' , Au', Au'', Au'', Ag', Ag=' , Hg', Hg'', Ni ,
Ni', Niz' Ni'', Pd , Pd', Pdz', Pt , Pt', Pt'2, pt'', Pt'4, Rh',
Rh" , Rh'' , Rh ' , Co' , Co", Co'', Ir , Ir', Ir-' , Ir'', Ir ' , Fe",
Fe3', Ru" , Ru'' , Ru4' , Rus' , Ru ' , Os2' , Os'', Osa' , Re", Re'' , Re ' ,
Re'* , Re'', Mn", Mn'' , Mna' , Cr2', Cr'' , 1.10 , Mo', Mo2' , Mo'' , W2' ,
W'' ,vz' , V'' , V ' , V5' , Nb'' , Nb'' , Nb ' , Nbs' , Ta'' , Taa', Tas' ,
Zn'
and Zn" ;
X' may be, for example, selected from the group
consisting of halogen, OH, (O) ;,,, C,-C,-alkoxv, (SO,) 11.,
(PO,) 1/3, (HPO;) 1/2, (H:PO~) , triflate, hexafluorophosphate,
methanesulfonate, arylsulfonate (preferably benzenesulfonate
or toluenesulfonate) , SeR14, CN, NC, SCN, CNS, OCN, CNO, N, and
R'SCO,, where R14 is as defined above and R15 is H or a straight
or branched C,-C6 alkyl group (preferably methyl) or aryl
(preferably phenyl) which may be substituted from 1 to 5 times
with a halogen (preferably 1 to 3 times with fluorine or
chlorine); and
n is the formal charge on the metal (e.g., 0 < n< 7).
Suitable ligands for use in the present invention include
compounds having one or more nitrogen, oxygen, phosphorus
and/or sulfur atoms which can coordinate to the transition
metal through a o-bond, ligands containing two or more carbon
atoms which can coordinate to the transition metal through a
7-bond, ligands having a carbon atom which can coordinate to
the transition metal through a o-bond but which do not form a
- 46 -
CA 02585469 2007-05-03
carbon-carbon bond with the monomer under the conditions of
the polymerizing step (e.g., ligands which do not participate
in u-addition reactions with (coordinated) monomers; see,
e.g., the ligand(s) described by van de Kuil et al, supra; and
van Koten et al, Recl. Trav. Chim. Pays-Bas, 113, 267-277
(1994)), and ligands which can coordinate to the transition
metal through a -bond or a~-bond.
Preferred N-, 0-, P- and S- containing ligarids may have
one of the follocaing formulas:
R16-Z-R" or
R"-Z- ( Rie-Z ) -R"
where:
R" and R17 are independently selected from the group
consisting of H, C.-C-., alkyl, aryl, heterocyclyl, and C? -C6
alkyl substituted with C1-C6 alkoxy, C:-C, dialkylamino,
C(=Y) R', C(=Y) R'R' and/or YC (=Y) R , where Y, R5, R6, R' and R3
are as defined above; or
R" and R17 can be joined to form a saturated, unsaturated
or heterocyclic ring as described above for the "heterocyclyl"
group;
Z is 0, S, NR19 or PR19, where R19 is selected from the same
group as R16 and R",
each R'a is independently a divalent group selected from
the group consisting of C_-C4 alkylene (alkanediyl) and C.-Cq
alkenylene where the covalent bonds to each Z are at vicinal
- 47 -
CA 02585469 2007-05-03
positions (e.g., in a 1,2-arrangement) or at 9-positions
(e.q., in a 1,3-arrangement) and C1-CB cycloalkanediyl, C,-C9
cycloalkenediyl, arenediyl and heterocyclylene where the
covalent bonds to each Z are at vicinal positions; and
m is from 1 to 6.
In addition to the above ligands, each of R16-Z and R17-Z
can form a ring with the R1e group to which the Z is bound to
form a linked or fused heterocyclic ring svstem (such as is
described above for "heterocyclyl"). Alternatively, when R'6
and/or R" are heterocvclyl, Z can be a covalent bond (which
may be single or double), CH: or a 4- to 7-membered ring fused
to R16 and/or R17, in addition to the definitions given above
for Z. Exemplary ring systems for the present ligand include
bipyridyl, bipyrrole, 1,10-ahenanthroline, a cryptand, a crown
ether, etc.
Where Z is PR19, R19 can also be C1-C,o-alkoxy.
Also included as suitable lictands in the present
invention are Co (carbon monoxide), porphyrins and
porphycenes, the latter two of which may be substituted with
from 1 to 6 (preferably from 1 to 4) halogen atoms, C1-C, alkyl
groups, C1-C6-alkoxy groups, C1-C6 alkoxycarbonyl, aryl groups,
heterocyclyl groups, and C.-C6 alkyl groups further substituted
with from 1 to 3 halogens.
Further ligands suitable for use in the present invention
include compounds of the formula R20R21C (C (=Y) RS) z, where Y and
R5 are as defined above, and each of R20 and RZ' is
- 48 -
CA 02585469 2007-05-03
independently selected from the aroup consisting of H,
halogen, C,-C0 alkyl, aryl and heterocyclyl, and P.20 and R21 may
be joined to form a C3-C8 cycloalkyl ring or a hydrogenated
(i.e., reduced, non-aromatic or partially or fully saturated)
aromatic or heterocyclic ring (consistent with the definitions
of "aryl" and "heterocyclyl" above), any of which (except for
H and halogen) may be further substituted with 1 to 5 and
preferably 1 to 3 C1-C6 alkyl groups, C.-C6 alkoxy groups,
halogen atoms and/or aryl groups. Preferably, one of R" and
R21 is H or a negative charge.
Additional suitable ligands include, for example,
ethylenediamine and propylenediamine, both of which may be
substituted from one to four times on the amino nitrogen atom
with a C1-C4 alkyl group or a carboxymethyl group; aminoethanol
and aminopropanol, both of which may be substituted from one
to three times on the oxygen and/or nitrogen atom with a C:-C4
alkyl group; ethylene glycol and propylene glycol, both of
which may be substituted one or two times on the oxygen atoms
with a C,-C4 alkyl group; diglyme, triglyme, tetraglyme, etc.
Suitable carbon-based ligands include arenes (as
described above for the "aryl" group) and the cyclopentadienyl
ligand. Preferred carbon-based ligands include benzene (which
may be substituted with from one to six C1-C4 alkyl groups
[e.g., methyl]) and cyclopentadienyl (which may be substituted
with from one to five methyl groups, or which may be linked
through an ethylene or propylene chain to a second
- 49 -
CA 02585469 2007-05-03
cyclopentadienyl ligand). Where--the cyclopentadienyl ligand
is used, :t may not be necessary to include a counteranion
(X') in the transition metal compound.
Preferred ligands include unsubstituted and substituted
pyridines and bipyridines (where the substituted pyridines and
bipyridines are as described above for "heterocyclyl"),
acetonitrile, (R10O) ,P, PR103, 1, l0-phenanthroline, porphyrin,
cryptands such as K,,: and crown ethers such as 18-crown-6.
The most preferred ligands are bipyridyl, 4,4'-dialkyl-
bipyridyls and (R10O),P.
A preformed transition metal-ligand compler, can be used
in place of a mixture of transition metal compound and ligand
without affecting the behavior of the polymerization.
The present invention also concerns an improved atom or
group transfer radical polymerization process employing a
solubilized catalyst, which in a preferred embodiment, results
in a homogeneous polymerization system. T_n this embodiment,
the method employs a l4-gand having substituents rendering the
transition metal-ligand complex at least partially soluble,
preferably more soluble than the corresponding complex in
which the ligand does not contain the substituents, and more
preferably, at least 90 to 99% soluble in the reaction medium.
In this embodiment, the ligand may have one of the
formulas R16-Z-Rl7, R16-Z-(Rle-Z)m-Rl' or R20R21C(C(=Y)RS)Z above,
where at least one of R'6 and R17 or at least one of R2 0 and R21
are C_-C. alkyl, C1-C6 alkyl substituted with C:-C6 alkoxy
- 50 -
CA 02585469 2007-05-03
and/or C1-C4 dialkylamino, or are aryl or heterocyclvl
substituted with at least one aliphatic substituent selected
from the group consisting of C,-C.o alkyl, C,-C,o alkylene, CZ-C:o
alkynylene and aryl such that at least two, preferably at
least four, more preferably at least six, and most preferably
at least eight carbon atoms are members of the aliphatic
substituent(s). Particularly preferred ligands for this
embodiment of the invention include 2,2'-bipyridyl having at
least two alY.yl substituents containing a total of at least
eiqht carbon atoms, such as 4,4'-di-(5-nonyl)-2,2'-bipyridyl
(dNbipy) , 4,d'-di-n-heptyl-2,2'-bipyridyl (dHbipy) and 4,4'-
di-tert-butyl-2,2'-bipyridyl (dTbipy)
Particularly when combined with the aforementioned
process for polymerizing a monomer in the presence of a small
amount of transition metal redox conjugate, a substantial
improvement in product polvdispersity is observed. Whereas
heterogeneous ATRP yields polvmers with polydispersities
generally ranging from 1.1 to 1.5, so-called "homogeneous
ATRP" (e.g., based on dNbipy, dHbipy or dTbipy) with
transition metal redox conjugate present (e.g., Cu(I)/Cu(II))
yields polymers with polydispersities ranging from less than
1.05 to 1.10.
In the present polymerization, the amounts and relative
proportions of initiator, transition metal compound and ligand
are those effective to conduct ATRP. Initiator efficiencies
with the present initiator/transition metal compound/ligand
- 51 -
CA 02585469 2007-05-03
system are generally very good (e.g., at least 25%, preferably
at least 50%, more preferably > 80%, and most preferably >
90%) Accordingly, the amount of initiator can be selected
such that the initiator concentration is from 10'4 M to 3 M,
preferably 10-1-10'1 M. Alternatively, the initiator can be
present in a molar ratio of from 10"a:i to 0.5:1, preferably
from 10-3:1 to 5 x 10"2:1, relative to monomer. An initiator
concentration of 0.1-1 1=1 is particularly useful for preparing
end-functional polymers.
The molar proportion of transition metal compound
relative to initiator is generally that which is effective to
polymerize the selected monomer(s), but may be fiom 0.0001:1
to 10:1, preferably from 0.1:1 to 5:1, more preferably from
0.3:1 to 2:1, and most preferably from 0.9:1 to 1.1:1.
Conducting the polymerization in a homogeneous system may
permit reducing the concentration of transition metal and
ligand such that the molar proportion of transition metal
compound to initiator is as low as 0.001:1.
Similarly, the molar proportion of ligand relative to
transition metal compound is generally that which is effective
to polymerize the selected monomer(s), but can depend upon the
number of coordination sites on the transition metal compound
which the selected ligand will occupy. (One of ordinary skill
understands the number of coordination sites on a given
transition metal compound which a selected ligand will
occupy.) The amount of ligand may be selected such that the
- 52 -
CA 02585469 2007-05-03
ratic of (a) coordination sites on the transition metal
compound to (b) coordination sites which the ligand will
occupy is from 0.1:1 to 100:1, preferably from 0.2:1 to 10:1,
more preferably from 0.5:1 to 3:1, and most preferably from
0.8:1 to 2:1. However, as is also known in the art, it is
possible for a solvent or for a monomer to act as a ligand.
For the ourposes of this application, however, the monomer is
preferably (a) distinct from and (b) not included within the
scope of the ligand, although in some embodiments (e.g., the
present process for preparing a graft and/or hyperbranched
(co) polymer), the monomer may be self-initiating (i.e.,
capable of serving as both initiator and monomer).
Nonetheless, certain monomers, such as acrylonitrile, certain
(meth)acrylates and styrene, are capable of serving as ligands
in the present invention, independent of or in addition to
their use as a monomer.
~/,'I The present polymerization may be conducted in the
absence of solvent ("bulk" polymerization). However, when a
solvent is used, suitable solvents include ethers, cyclic
ethers, CS-Clo alkanes, CS-Ce cycloalkanes which may be
substituted with from 1 to 3 C1-C4 alkyl groups, aromatic
hydrocarbon solvents, halogenated hydrocarbon solvents,
acetonitrile, dimethylformamide, ethylene carbonate, propylene
carbonate, dimethylsulfoxide, dimethylsulfone, water, mixtures
of such solvents, and supercritical solvents (such as CO21 C1-
C4 alkanes in which any H may be replaced with F, etc.). The
- 53 -
CA 02585469 2007-05-03
presenL polymerization may also be conducted in accordance
with known suspension, emul=ion, miniemulsion, gas phase,
dispersion, precipitation and reactive injection molding
polymerization processes, particularly mimiemulsion and
dispersion polymerization processes.
Suitable ethers include compounds of the formula R1.2OR2',
in which each of P.'2 and R2' is independently an alkyl group of
from 1 to 6 carbon atoms or an aryl group (such as phenyl)
which may be further substituted with a C1-Ca-alkyl or C,-C,-
alkoxy group. Preterably, when one of R" and R23 is methyl,
the other of R22 and RzJ is alkyl of from 4 to 6 carbon atoms,
C1-C,-al;coxyethyl or p-methoxyphenyl. Examples include diethyl
ether, ethyl propyl ether, dipropyl ether, methyl t-butyl
ether, di-t-butyl ether, glyme (dimethoxyethane), diglyme
(diethylene glycol dimethyl ether), 1,4-dimethoxybenzene, etc.
Suitable cyclic ethers include THF and dioxane. Suitable
aromatic hydrocarbon solvents include benzene, toluene, o-
xylene, m-xylene, p-xylene and mixtures thereof. Suitable
halogenated hydrocarbon solvents include CH,Cl,, 1,2-
dichloroethane and benzene substituted from 1 to 6 times with
fluorine andJor chlorine, although preferably, the selected
halogenated hydrocarbon solvent(s) does not act as an
initiator under the polymerization reaction conditions.
ATRP may also be conducted either in bulk or in an
aqueous medium to prepare water-soluble or water-miscible
polymers. Water-soluble polymers are important scientifically
- 54 -
CA 02585469 2007-05-03
and commercially, because they find a wide range of
applications in mineral-processing, water-treatment, oil
recovery, etc. (Bekturov, E. A.; Bakauova, Z. K. Synthetic
Water-Soluble Polylners in Solution, Huethig and Wepf: Basel,
1986; Molyneux, P. Water-Soluble S_vnthetic Polymers:
Properties and Behavior, CRC Press: Boca Raton, Florida,
1991). Many of the industrially important water-soluble
polymers are prepared by the free-radical polymerization of
acrylic and vinyl monomers, because this polymerization
technique is amenable for use in aaueous solutions (Elias, H.
Vohwinkel, F. New Commerciai Polymers 2; Gordon and Breach:
New York, 1936). For these reasons, it is beneficial to
develop well-controlled radical polymerizations for use in
aqueous polymerizations (Keoshkerian, B.; Georges, M. K.;
Boils-Boissier, D. macromolecules 1995, 28, 6381).
Thus, the present ATRP process can be conducted in an
aqueous medium. An "aqueous medium" refers to a water-
containing mixture which is liquid at reaction and processing
temperatures. Examples include water, either alone or admixed
with a water-soluble C,-Ca alcohol, ethylene glycol, glycerol,
acetone, methyl ethyl ketone, dimethylformamide,
dimethylsulfoxide, dimethylsulfone, hexamethylphosphoric
triamide, or a mixture thereof. Additionally, the pH of the
aqueous medium may be adjusted to a desired value with a
suitable mineral acid or base (e.g., phosphoric acid,
- 55 -
CA 02585469 2007-05-03
hvdrochloric acid, ammonium hydroxide, t7aOH, 2JaHC0õ Na,COõ
etc.). However, the preferred aqueous medium is water.
When conducted in an aqueous medium, the polymerization
temperature may be from o C to the reflux temperature of the
medium, preferably from 20 C to 100 C and more preferably
from 70 C to 100 C. Preferably, the monomer(s) polymerized
in this embodiment are at least partially water-soluble or
water-miscible, or alternatively, capable of being polymerized
in an aqueous emulsion which further comprises a surfactant
(preferably in an amount sufficient to emulsify the
monomer(s). Such monomers are preferably sufficiently soluble
in 80 C water to provide a monomer concentration of at least
10"' 1=1, and more preferably 10"' M.
Suitable water-soluble or water-miscible monomers include
those of the formula:
R' R'
C=C
R2 R4
wherein R1 and Rz are independently selected from the group
consisting of H, halogen, CN, straight or branched alkyl of
from 1 to 10 carbon atoms (preferably from 1 to 6 carbon
atoms, more preferably from 1 to 4 carbon atoms) which may be
substituted, a,O-unsaturated straight or branched alkenyl or
alkynyl of 2 to 10 carbon atoms (preferably from 2 to 6 carbon
- 56 -
CA 02585469 2007-05-03
atoms, more preferably from 2 to 4 carbon atoms) which may be
substituted, C,-Ce cycloalkyl which may be substituted, NR82,
N'R'3, C(=Y)R5, C(=Y)NR'R', YC(=Y)R8, YC(=Y)YRe, YS(=Y)R8,
YS (=Y) 2R4, YS (=Y) 2YRe, P(Ra) Z, P(=Y) (Re) 2, P(YRe) z, P(=Y) (YRe) 2,
P( YR8 ) R6 , P(1) ( YRB ) Re , and aryl or heterocyclyl (as defined
above) in which one or more nitrogen atoms (if present) may be
= quaternized with an R8 group (preferably H or C1-Cq alkyl);
where Y may be NRe, S or O(preferably O), RS is alkyl of from
1 to 10 carbon atoms, alkoxy of from 1 to 10 carbon atoms,
aryl, aryloxy or heterocyclyloxy; R' and R' are independently H
or alkyl of from 1 to 20 carbon atoms, or R6 and R' may be
joined together to form an alkylene group of from 2 to 5
carbon atoms, thus forming a 3- to 6-membered ring; and R6 is
(independently) H, straight or branched C1-Clo alkyl (which may
be joined to form a 3- to 8-membered ring where more than one
Ra group is covalently bound to the same atom) or aryl, and
when Ra _s directly bonded to S or 0, it may be an alkali metal
or an ammonium (N'Rg, ) group; and
R' and R' are independently selected from the group
consisting of H, halogen (preferably fluorine or chlorine),
CN, C,-C6 (preferably C1) alkyl and C00R9 (where R9 is as
defined above); or
Rl and R' may be joined to form a group of the
formula (CH,),,, (which may be substituted) or C(=O) -Y-C (=0) ,
- 57 -
CA 02585469 2007-05-03
where n' is from 2 to 6 (preferably 3 or 4) and Y is as
defined above;
at least two of R1, R', R3 and R" are H or halogen;
and at least one of R', RZ, R' and Ra in at least one monomer
is, or is substituted with, OH, 23R8õ N'Ra3, COOR', C(=Y)R5,
C(=Y)NR6R', YC(=Y)Rd, YC(=Y)YRe, YS(=Y)RB, YS(=Y)2RB, YS(=Y)ZYRe,
P ( YRa ) : , P ( =Y ) ( YRe ) z , P ( YRd ) R8 , P ( =Y ) ( YRB ) Rd , P ( =Y
) Re,, hydroxy-
substituted G-C, alkvl or hetercyclyl in which one or more
nitrogen atoms is ouaternized with an Ra aroup (e.g., H or C.-
C4 a lky l ) .
A group "which may be substituted" refers to the alkyl,
alkenyl, alkynyl, aryl, heterocvclyl, alkylene and cycloalkyl
groups substituted in accordance with the descriptions herein.
A preferred monomer is a sulfonated acrylamide.
The present invention also encompasses water swellable
polvmers and hydrogels. Hydrogels are polymers which, in the
presence of water, do not dissolve, but absorb water and thus
swell in size. -These polymers have found wide applications
ranging from drug delivery to oil recovery. Generally, these
polymeric materials are synthesized by radical polymerization
of a water-soluble material in the presence of a divinyl
monomer. The divinyl monomer introduces chemical cross links
which makes the polymer permanently insoluble in any solvent
(i.e., without degrading the polymer and its physical
properties).
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The present ATRP process also provides a process --for
synthesizing a hydrogel which utilizes physical cross links
between chains and which allows for dissolution of the polymer
without loss of physical properties. The present water
swellable polymers and hydrogel polymers can also be processed
from a melt, a characteristic that polvmers having chemical
crosslinks lack. The water-soluble mono~ers described above
may be used to prepare the present water swellable
(co)polvmers and hydroaels. An exemplary polymer which was
synthesized to demonstrate such abilities is poly(N-
vinylpyrrol:-'dinone-g-styrene) (see the Examples below).
In a preferred embodiment, the hydrogel comprises a base
(co)polymer and at least two (preferably at least three, more
preferably at least four, and even more preferably at least
five) relatively hydrophobic side-chains grafted thereonto
(e.g., by conventional radical polymerization or by the
present nTRP process). The base (co)polymer may be a
(co)polymer containing a water-soluble or water-miscible
monomer in an amount sufficient to render the (co)polymer
water-soluble or water-miscible (e.g., containing at least 10
mol.o, preferably at least 30 mol.a, and preferably at least
50 mol.% of the water-soluble or water-miscible monomer).
Preferred hydrophobic side-chains contain monomeric units of
the formula -R'R'C-CR'R4-, in which:
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R' and R' are independently selected from the group
consiszing of H, halogen, CN, straight or branched alkyl of
from 1 to 10 carbon atoms (preferably from 1 to 6 carbon
atoms, more preferably from 1 to 4 carbon atoms) which may be
substituted, straight or branched alkenyl or alkynyl of from 2
to 10 carbon atoms (preferably from 2 to 6 carbon atoms, more
preferably from 2 to 3 carbon atoms) which may be substituted,
C3-C8 , cycloalkyl which may be substituted, NRe:, C(=Y) R5,
C(=Y)NR R', ':C(=Y)R", 'zC(=Y)YRd, YS(=Y)P. , YS(=Y)2Re, YS(=Y)2YRa,
P(Ra)z, P(=Y) (Re)zr P(YRe)zi P(=Y) (YRa) , P(YR8)Re, P(=Y) (YR8)Re,
and aryl or heterocyclyl in which each H atom may be replaced
with halogen atoms, i1R8õ C:-CSalk.yl or C:-C6 alkoxy groups;
where Y may be IdRe, S or 0 (preferably 0) ; R5 is alkyl of from
1 to 10 carbon atoms, alkoxy of from 1 to 10 carbon atoms,
aryl, aryloxy or heterocyclyloxy; R6 and R' are alkyl of from 1
to 20 carbon atoms, or R and R' may be joined together to form
an alkylene group of from 2 to 7 carbon atoms, thus -forming a
3- to 8-membered ring; and Re is (independently) straight or
branched C.-C.o alkyl (which may be joined to form a 3- to 7-
membered ring where more than one R8 group is covalently bound
to the same atom); and
R' and R' are independently selected from the group
consisting of H, halogen (preferably fluorine or chlorine),
CN, C1-C6 (preferably C:) alkyl and COOR9 (where R9 is alkyl of
from 1 to 10 carbon atoms or aryl);
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R' and P.' may be joined to form a group of the
formula (CH2)n. (which may be substituted) where n' is from 2
to 6 (preferably 3 or 4); and
at least two of R1, R', R' and R' are H or halogen.
Polymers produced by the present process may be useful in
general as molding materials (e.g., polvstyrene containers)
and as barrier or surface materials (e.g., poly(methyl
methacrylate), or PMMA, is well-known in this regard as
PLEXIGLAS'"). However, the polymers produced by the present
process, which typically will have uniform, predictable,
controllable and/or tunable properties relative to polymers
produced by conventional radical polymerization, will be most
suitable for use in specialized or performance applications.
For example, block copolymers of polystyrene and
polyacrylate (e.g., PSt-PA-PSt triblock ccpolymers) are useful
thermoplastic elastomers. Poly(methvl methacrylate)-
polyacrylate triblock copolymers (e.g., PMMA-PA-MMA) are
useful, fully acrylic thermoplastic elastomers. Homo- and
copolymers of styrene, (meth)acrylates and/or acrylonitrile
are useful plastics, elastomers and adhesives. Either block
or random copolymers of styrene and a(meth)acrylate or
acrylonitrile may be useful thermoplastic elastomers having
high solvent resistance.
Furthermore, block copolymers in which the blocks
alternate between polar monomers and non-polar monomers
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CA 02585469 2007-05-03
produced by the present invention are useful amphiphilic
surfactants or dispersants for making highly uniform polymer
blends. Star polymers produced by the present process are
usefu'_ high-impact (co)polymers. (For example, STYROLUX'", an
anionically-polymerized styrene-butadiene star block
copolymer, is a}:nown, useful high-impact copolymer.)
The (co)polymers of the present invention (and/or a block
thereof) may have an average dearee of polymerization (DP) of
at least 3, preferably at least 5, and more preferably at
least 10, and may have a weight and/or number average
molecular weight of at least 250 g/mol, preferably at least
500 g/mol, more preferably at least 1,000 g/mol, even more
preferably at least 2,000 g/mol, and most preferably at least
3,000 g/mol. The present (co)polymers, due to their "living"
character, can have a maximum molecular weight without limit.
However, from a practical perspective, the present
(co)polymers and blocks thereof may have an upper weight or
number average molecular weight of, e.g., 5,000,000 g/mol,
preferably 1,000,000 g/mol, more preferably 500,000 g/mol, and
even more preferably 250,000 g/mol. For example, when
produced in bulk, the number a-/erage molecular weight may be
up to 1,000,000 (with a minimum weight or number average
molecular weight as mentioned above).
The number average molecular weight may be determined by
size exclusion chromatography (SEC) or, when the initiator has
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a group which can be easily distinguished from the monomer(s),
by NMR spectroscopy (e.g., when 1-phenylethyl chloride is the
initiatcr and methyl acrylate is the monomer).
Thus, the present invention also encompasses novel end-
functional, telechelic and hyperbranched homopolymers, and
block, multi-block, star, gradient, random, graft or "comb"
and hyperbranched copolymers. Each of the these different
types of copolymers will be described hereunder.
Because ATRP is a "living" polymerization, it can be
started and stopped, practically at will. Further, the
polymer product retains the functional group "X" necessary to
initiate a further polymerization. Thus, in one embodiment,
once the first monomer is consumed in the initial polymerizing
step, a second monomer can then be added to form a second
block on the growing polymer chain in a second polymerizing
step. Additional polymerizations with the same or different
monomer(s) can be performed to prepare multi-block copolymers.
Furthermore, since ATRP is radical polymerization, blocks
can be prepared in essentially any order. One is not
necessarily limited to preparing block copolymers where the
sequential polymerizing steps must flow from the least
stabilized polymer intermediate to the most stabilized poly-mer
intermediate, such as is necessary in ionic polymerization.
Thus, one can prepare a multi-block copolymer in which a
polyacrylonitrile or a poly(meth)acrylate block is prepared
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CA 02585469 2007-05-03
first, then a styrene or butadiene block is attached thereto,
etc.
As is described throughout the application, certain
advantageous reaction design choices will become apparent.
However, one is not limited to those advantageous reaction
design choices in the present invention.
Furthermore, a linking group is not necessary to join the
different blocks of the present bloc}: copolymer. One can
simply add successive monomers to form successive blocks.
Further, it is also possible (and in some cases advantageous)
to first isolate a (co)polymer produced by the present ATRP
process, then react the polymer with an additional monomer
using a different initiator/catalyst system (to "match" the
reactivity of the growing polymer chain with the new monomer).
In such a case, the product polymer acts as the new initiator
for the further polymerization of the additional monomer.
Thus, the present invention also encompasses end-
functional homopolymers having a formula:
A-[ (M')nI -X
and random copolymers having a formula:
A-[(Ml)i (W);]-X
A"[ (M')i (MZ)j (M3)k)-X or
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A- C (14'(M')_(243 )~... (M")-}{
where A may be R11R'2R'3C, R1'R'2 R"Si, (R11)R,Si, R'1Ri2P1, (RL1)õP,
(R"0),,p, (Rti) (R1z(D)p, (RIi)nP(0), (R"O)r,P(O) or (R11) (R1s0)p(0)
R" , Rl2, Rl' and X are as def ined above; t1 ', t=i2 , 1=i' ,... up to M"
are each a radically polymerizable monomer (as defined above);
h, i, j, k... up to 1 are each average degrees of
polymerization of at least 3; and i, j, }:... up to 1 represent
molar ratios of the radically polymeri7able monomers 1=1', t=i2,
t2' , . . . up to M .
Preferably, at least one of Id', 2, ii', ... up to t-tu has the
formula:
R1 R'
\ /
C=C
/ \
R2 R
wherein at least one of R' and R2 is Cti, CFõ straight or
branched alkyl of from 4 to 20 carbon atoms (preferably from 4
to 10 carbon atoms, more preferably from 4 to 8 carbon atoms),
C,-C9 cycloalkyl, aryl, heterocyclyl, C(=Y ) R5 , C(=Y ) NRbR' and
YC(=Y)RB, where aryl, heterocyclyl, Y, R5, R6, R' and R8 are as
defined above; and
R' and R' are as def ined above; or
R' and R' are j o ined to form a group of the formula ( CHz ),,.
or C(=O)-Y-C(=0), where n' and Y are as defined above.
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Preferably, these (co)polymers have either a weight or
number average molecular weiaht of at least 250 g/mol, more
preferably at least 500 g/mol, even more preferably 1,000
g/mol and most preferably at least 3,000 g/mol. Preferably,
the (co)polymers have a polydispersity of 1.50 or Less, more
preferably 1.35 or less, even more preferably 1.25 or less and
most preferably 1.20 or less. Although the present gels may
have a weight or number average molecular weight well above
5,000,000 q/mol, from a practical persoective, the present
(co)polymers and blocks thereof may have an upper weight or
number average molecular weight of, e.g., 5,000,000 g/mol,
preferably 1,000,000 g/mol, more preferably 500,000 g/mol, and
even more preferably 250,000 g/mol.
Preferred random copolymers include those prepared from
any combination of styrene, vinvl acetate, acrylonitrile,
acrylamide and/or C_-Co alkyl (meth)acrylates, and particularly
include those of (a) methyl methacrylate and stvrene having
from 10 to 75 molo styrene, (b) methyl methacrylate and methyl
acrylate having from 1 to 75 molo methyl acrylate, (c) styrene
and methyl acrylate, and (d) methyl methacrylate and butyl
acrylate.
The present invention also concerns block copolymers of
the formula:
A- (Ml) P- (MZ) q-X
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A-(I=11)P-(M2)q-(M3)r-X
A-(I=1')P-(Idl )Q-(M')r-...-(M")5-X
wherein A and X are as defined above; M' , I=12 , M3, ... up to M.
are each a radically polymerizable monomer (as defined above)
selected such that the monomers in adjacent blocks are not
identical (although monomers in non-adjacent blocks may be
identical) and p, q, r,... up to s are independently selected
such that the average degree of polymerization and/or the
weight or number average molecular weight of each block or of
the copolymer as a whole may be as described above for tlie
present (co)polymers. After an appropriate end group
conversion reaction (conducted in accordance with known
methods) , X may also be, for example, H, OH, Idõ NHõ COOH or
CONH,.
Preferred block copolymers may have the formula
RiiRi2Ri3C_ (Mi) p_ (M2) q-X
RiiRi2Ri3C- (M1) P- (M2) q- (M') r-X or
R"R12 R13C_ (1,,11) p- (M2) q- (M3) r-. . . - (2''1") 9-X
Preferably, each block of the present block copolymers has a
polydispersity of 1.50 or less, more preferably 1.35 or less,
even more preferably 1.25 or less and most preferably 1.20 or
less. The present block copolymer, as a complete unit, may
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CA 02585469 2007-05-03
have a polydispersity of 3.0 or less, more preferably 2.5 or
less, even more preferably 2.0 or less and most preferably
1.50 or less.
The present invention may be used to prepare periodic or
alternating copolymers. The present ATRP process is
particulariy useful for producing alternating copolymers where
one of the monomers has one or two bulky substituents (e.g.,
where at least one of 24' , 1=12, m' ,... up to A1" are each 1, 1-
diarylethylene, didehydromalonate C_-C- diesters, C,-C,o
diesters of maleic or fumaric acid, maleic anhydride and/or
maleic diimides [where Y is NRB as defined above], etc.), from
which homopolymers may be difficult to prepare, due to steric
considerations. Thus, some preferred monomer combinations for
the present alternating copolymers containing "bulky"
substituents include combinations of stvrene, acrylonitrile
and/or C.-C5 esters of (meth)acrylic acid, with maleic
anhydride, C,-C9 alkyl maleimides and/or 1,1-diphenylethylene.
Copolymerization of monomers with donor and acceptor
properties results in the formation of products with
predominantly alternating monomer structure (Cowie,
"Alternating Copolymerization," Comprehensive Polymer Science,
vol. 4, p. 377, Pergamon Press (19B9)). These copolymers can
exhibit interesting physical and mechanical properties that
can be ascribed to their alternating structure (Cowie,
Alternating Copolymers, Plenum, New York (1985)).
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So-called "alternating" copolymers can be produced using
the present method. "Alternating" copolvmers are prepared by
copolymerization of one or more monomers having electron-donor
properties (e.g., unsaturated hydrocarbons, vinyl ethers,
etc.) with one or more monomers having electron acceptor type
properties (acrylates, methacrylates, unsaturated nitriles,
unsaturated ketones, etc.). Thus, the present invention also
concerns an alternating copolvmer of the formula:
A- ( M'-M2 ) P-X
A- (M'-M2 ) P- ( M2-M ') q-X
A- (M'-M~) p- (M2-M') q- (M'-iqz) r'X or
A-[ (M'-MZ) p- (M2-!=il) q- (?=1'-i=12) t-. . - (i=1"-M'') 5-X
where A and X are as def ined above,M' and t-i' are dif f erent
radically-polymerizable monomers (as defined above), and 1=i" is
one of M' and 2=12 and MY is the other of tV and M~. However, p,
q, r,... up to s are independently selected such that the
average degree of polymerization andJor the weight or number
average molecular weight of the copolymer as a whole or of
each block may be described above for the present end-
functional or random (co)polymers. (The description "r... up
to s" indicates that any number of blocks equivalent to those
designated by the subscripts p, q and r can exist between the
blocks designated by the subscripts r and s.)
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Preferably, : is R11R'2 R"C, I-I' is one or more monomers
having electron-donor properties (e.g., C2-C,, unsaturated
hydrocarbons which may have one or more alkyl, alkenyl,
alkynyl, alkoxy, alkylthio, dialkylamino, aryl or tri(alkyl
and/or aryl)silyl substituents as defined above [e.g.,
isobulene or vinyl C,-C,o ethers], etc.) and i=i' is one or more
monomers having electron acceptor properties
(e.g., (meth) acrylic acid or a salt thereof, C,-C,
(meth)acrvlate esters, C,-C_c unsaturated nitriles, C;-C2, a,)3-
unsaturated aldehvdes, ketones, sulfones, phosphates,
sulfonates, etc., as defined above).
Preferably, the present alternating copolymers have
either a weight or number average molecular weight of at least
250 g/mol, more preferably 500 g/mol, even more preferably
1,000 g/mol, and most preferably 3,000 g/mol. Preferably, the
present alternating copolymers have a maximum weight or number
average molecular weight of 5,000,000 g/mol, preferably
1,000,000 g/mol and even more preferably 500,000 g/mol,
although the upper the limit of the molecular weight of the
present "living" (co)polymers is not limited. Preferably, the
present alternating copolymers have a polydispersity of 1.50
or less, more preferably 1.35 or less, even more preferably
1.25 or less and most preferably 1.20 or less.
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The present random or alternating copolymer can also
serve as a block in any of the present block, star, graft,
comb or hyperbranched copolymers.
Where the A (or preferably R11R12RL3C) group of the
initiator contains a second "X" group, ATRP may be used to
prepare "telechelic" (co)polymers. "Telechelic" homopolymers
may have the following formula:
X-rL,- ( A ) -?~I.,-:=:
where A (preferably R"R1'Rl'C) and are as defined above, 2=1 is
a radically polymerizable monomer as defined above, and p is
an average degree of polymerization of at least 3- , subject to
the condition that A is a group bearing an X substituent.
Preferred telechelic homopolymers include those of
styrene, acrylonitrile, C.-C, esters of (meth)acrylic acid,
vinyl chloride, vinyl acetate and tetrafluoroethylene. Such
telechelic homopolymers preferably have either a weight or
number average molecular weight of at least 250 g/mol, more
preferably at least 500 g/mol, even more preferably at least
1,000 g/mol, and most preferably at least 3,000 g/mol, and/or
have a polydispersity of 1.50 or less, more preferably 1.3 or
less, even more preferably 1.2 or less and most preferably
1.15 or less. From a practical standpoint, the present
alternating copolymers may have a maximum weight or number
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CA 02585469 2007-05-03
average molecular weight of 5,000,000 g/mol, preferably
1,000,000 g/mol, more preferably 500,000 g/mol, and even more
preferably 250,000 g/mol, although the upper limit of the
molecular weight of the present "living" (co)polymers is not
oarticularly limited.
Block copolymers prepared by ATRP from an initiator
having a second "v" group may have one of the following
formulas:
X-(i'1')q-(M')p-(A) -(14')p-(M')q-h
X-(M')-(M2)4-(i4')p-(A)-(M')p-(M2)q-(M')-ri
X-(Mu)5-. . .-(M3)r-(M2)q-(rd')p-A-(M')p-(MZ)q-(M3)r-.. .-(M")s-X
and random copolymers may have one of the following formulas:
X-( (1'11)n(M2)q~-(A) -~ (M')p(2=1Z)-X
};-( (I'i~)p(r'1')q(i'1')r)(A)-( (r11)p(I=12)q(M):: -X
}:-[ (M')p... (M')q(t'1'),-(M")J -a-[ (r'1')p(W)q(M3)r... (M")97-X
where A (preferably R11R12R13C) , X, M1, MZ, M3, ... up to M", and
p, q, r,... up to s are as defined above, subject to the
condition that A is a group bearing an X substituent.
The present invention also concerns gradient copolymers.
Gradient copolymers form an entirely new class of polymers
with a controlled structure and composition which changes
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CA 02585469 2007-05-03
gradually and in a svstematic and predictable manner along the
copolvmer chain- Due to this composition
distribution and consequent unusual interchain interactions,
gradient copolymers are expected to have very unique thermal
properties (e.g., glass transition temperatures and/or melting
points). They may also exhibit unprecedented phase separation
and uncommon mechanical behavior, and mav provide unique
abilities as surfactants or as modifiers for blending
incomaatible materials.
Gradient copolymers can be obtained in a system without a
significant chain-breaking reaction, such as ATRP. To control
the copolymer composition, it is beneficial to maintain
continuous growth of the polymer chain and regulate the
comonomers' feed composition during the course of the
reaction. Otherwise, the distribution of the monomer units
along the polymer chain may be random or block-like.
To date, there are no publications on the subject of
gradient copolymers. The closest examples described so far
are tapered copolymers prepared through living anionic
polymerization (Sardelis et al, Polymer, 25, 1011 (1984) and
Polymer, 28, 244 (1987); Tsukuhara et al, Pol_vm. J., 12, 455
(1980)). Tapered copolymers differ from gradient copolymers
since they retain block-like character despite the composition
gradient in the middle block. Additionally, the compositional
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CA 02585469 2007-05-03
gradient of tapered polymers is inherent and cannot be changed
or controlled.
Gradient copolymers may be prepared via ATRP
copolymerization of two or more monomers with different
homopolymerization reactivity ratios (e.g., r= >> r2, where r'
may be greater than 1 and r2 may be less than 1) Such
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CA 02585469 2007-05-03
comonomers usually do not copolymerize randomly (Odian,
Principles of Polymerization, 3rd ed., John Wiley & Sons, New
York, p. 463 (1991)). For example, in conventional radical
polymerization, a mixture of homopolymers is obtained.
In the present controlled system, where the polymer chain
is not terminated at any stage of the reaction, initially only
the more (or most) reactive monomer reacts until its
concentration decreases to such a level that the less (or
second most) reactive monomer begins zo incorporate into the
growing polymer chains. The less reactive monomer is
gradually incorporated into the polymer chain to a greater
extent, and its content in the chain increases, as the more
reactive monomer is further consumed. Finally, only the least
reactive monomer is present in the system and as it reacts, it
forms a block of the least reactive monomer at the end of the
chain. The gradient of composition in such a copolymer is
controlled by the difference in the reactivity ratios and the
rate with which each of the monomers reacts. It might also be
considered an inherent control over the copolymer's
composition, which can be altered by intentionally changing
the concentration of one or more of the monomers.
Thus, in an example of the gradient copolymerization
including two distinct monomers, the polymerizing step of the
present method of controlled atom or group transfer
polymerization may comprise polymerizing first and second
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radically polymerizable monomers present in amounts providing
a molar ratio of the first monomer to the second monomer of
from a:b to b:a, where a and b are each from 0 to 100 and (a +
b) = 100, then adding an additional amount of the first and/or
second monomer providing a molar ratio of the first monomer to
the second monomer of from c:d to d:c, where c differs from a,
d differs from b and (c + d) = 100, and if desired, repeating
as often as desired the adding step such that if c > a, the
molar proportion (or percentage) of the first monomer
increases, but if d > b, the molar proportion (or percentage)
of the second monomer increases. The adding step(s) may be
continuous, in intermittent portions or all at once.
Thus, the present invention also encompasses a gradient
copolyTner of the formula:
A-I=tl..- 03Mzb) X-. . . - (M1crZ 2d) y-MzI-:1
where A and X are as defined above, t=il and mZ are radically-
polymerizable monomers (as defined above) having different
reactivities (preferably in which the ratio of
homopolymerization and/or copolymerization reactivity rates
are at least 1.5, more preferably at least 2 and most
preferably at least 3), a, b, c and d are non-negative numbers
independently selected such that a + b = c + d = 100, wherein
the a:b ratio is from 99:1 to 50:50, the c:d ratio is from
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CA 02585469 2007-05-03
50:50 to 99:1, and the molar proportion of M1 to MZ gradually
decreases along the length of the polymer chain from a:b to
c:d, and n, m, x and y are independently an integer of at
least 2, preferably at least 3, more preferably at least 5 and
most preferably at least 10. The weight or number average
molecular weight of each block or of the copolymer as a whole
may be as described above for the present (co)polymers.
Preferably, A is R'=R12R13C, and X is a halogen.
To determine the aradient, the copolymerization can be
interniittently sampled, and the molar proportion of units of
the copolymer corresponding to each monomer determined in
accordance with known methods. As long as the proportion of
one monomer increases as the other(s) decrease(s) during the
course of the copolymerization, the molar proportion of the
one monomer increases along the length of the polymer chain as
the other(s) decrease(s).
Alternativeiy, the decrease of the monomer ratio along
the length of the polymer chain a:b to c:d can be determined
in accordance with the numbers of monomer units alona the
polymer chain. The number of subblocks must be smaller than
the number of monomeric units in each subblock, but the
subblocks may overlap by a number of monomer units smaller
than the size of the subblock. For example, where the central
block of the polymer contains 6 monomeric units, the ratios
may be determined for two 3-unit subblocks (e.g., (3-mer)-(3-
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CA 02585469 2007-05-03
mer)). where the central block of the polymer contains, for
example 9 monomeric units, the ratios may be determined for
three 4-unit subblocks where the central subblock overlaps
each terminal subblock by one monomer unit (e.g., (4-mer)-
(overlapping 4-mer)-(4-mer). Where the central block of the
polymer contains, for example, from 10 to 50 monomeric units,
the ratios may be determined for 5- to lo-unit subblocks
(e.g., (5-mer)-(5-mer), (6-mer)-(8-mer)-(6-mer), (10-mer)-(10-
mer), (5-mer)-(5-mer)-(5-mer)-(5-mer), etc.). Where the
central block of the polymer contains, for example, from 51 to
380 monomeric units, the ratios may be determined for 10- to
20-unit subblocks; etc. Such copolvmers can be prepared by
carefully controlling the molar ratios of monomers to each
other and to initiator or dormant polymer chains.
In a further embodiment, the relative proportions of
first monomer to second monomer are controlled in a continuous
manner, using for example by adding the second monomer via a
programmable syringe or feedstock supply pump.
When either the initiator or monomer contains a
substituent bearing a remote (i.e., unconjugated) ethylene or
acetylene moiety, ATRP can be used to prepare cross-linked
polymers and copolymers.
The present invention is also useful for forming so-
called "star" polymers and copolymers. Thus, where the
initiator has three or more "':" groups, each of the "X" groups
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CA 02585469 2007-05-03
can serve as a polymerization initiation site. Thus, the
present invention also encompasses star (co)polymers of the
formula:
A'-[ (M1)p-XJZ
A'-[ (M1)p-(M2)q-X]z
A'-[ (Ml)p-(M2)q-(M') r-x]Z
A'-[ (M1)(t=tZ )q-(M3)~-. . (M-)s-}:]z
A' -[ (M1iM")-x 1:
A'-[ (M'~M2-h
A '- r, (M1iM2~M'k. . .M"i) -X]
where A' is the same as A with the proviso that R11 , Rlz and Rl'
combined contain from 2 to 5 X groups, where X is as defined
above; i.i', 1.11, 1d'.... 14" are as defined above for the present
block copolymers; and z is from 3 to 6.; Preferably, A' is
R11R12R1'C, and v is haloaen (preferably chlorine or bromine).
Initiators suitable for use in preparing the present star
(co) polymers are those in which the A (or preferably R11R"R13C)
group possesses at least three substituents which can be "X"
(as defined above). Preferably, these substituents are
identical to "X". Examples of such initiators include
compounds of the formula C6H,( CH,X ) y or CH,. ( CH,X) Y, , where X is a
halogen, x + y = 6, x' + y' = 4 and y and y' are each > 3.
Preferred initiators of this type include 2,2-
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CA 02585469 2007-05-03
bis(chloromethyl)-1,3-dichloropropane, 2,2-bis(bromomethyl)-
1,3-dibromopropane), a,a',a"-trichloro- and a,a',a"-
tribromocumene, and tetrakis- and hexakis(o:-chloro- and a-
bromomethyl) benzene), the most preferred being hexakis(a-
bromomethyl)benzene.
Branched and hvperbranched polymers may also be prepared
in accordance with the present invention. The synthesis of
hyperbranched polymers has been explored to develop dendritic
molecules in a single, one-pot reaction.
Conventional hyperbranched polymers are obtained by the
reaction of AB, monomers in which A and B are moieties
containing functional groups capable of reacting with each
other to form stable bonds. Because of the AB, structure of
the monomers, reaction of two monomers results in the
formation of a dimer with one A group and three B groups.
This process repeats itself by reaction with either monomer,
dimer, trimer, etc., in a similar fashion to provide step-wise
growth of polymers.
The resulting polymer chains have only one A group and
(n + 1) B groups, where n is the number of repeat units.
Polymers resulting from these reactions are sometimes highly
functionalized. These polymers, however, do not have
perfectly symmetrical architectures, but rather, are of
irregular shapes. This may be due to uneven growth of the
macromolecule in various directions.
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The present hyperbranched polymers have some of the
qualities of dendrimers, but may lack some properties of
perfect dendrimers. The cationic process described by Frechet
et al. (Science 269, 1080 (1995)) differs from the present
synthesis of hyperbranched polvmers not only in the mechanism
of polymerization, but also by extending the reaction to
primary benzyl halides.
The present invention also concerns a process for
preparing hyperbranched polymers (e.g., hyperbranched
polystyrene) by atom or group transfer radical polymerization
(ATRP), prefF.rably in "one-pot" (e.g., in a single reaction
sequance without substantial purification steps, and more
specifically, in a single reaction vessel without any
intermediate purification steps), using the present process
and at least one radically polymerizable monomer in which at
least one of R', Rz, R' and R also contains a radically
transferable X group, optionally in the absence of an
initiator (or if an initiator is used, the X group of the
monomer may be the same or different from the X group of the
initiator).
For example, commercially available p-chloromethylstyrene
(p-CMS) may be polymerized in the presence of a transition
metal compound (e.g., Cu(I)) and ligand (e.g., 2,2'-bipyridyl,
or "bipy"). A demonstrative example of the copolymerization
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of styrene and p-C2=iS, and its comparison with a linear
standard, is presented in the Examples below.
In fact, the monomer may also act as initiator (e.g., the
homopolymerization of p-CMS in the presence of Cu(I) and
bipy). It is possible to remove the chlorine atom at the
benzylic position homolytically, thus forming Cu(II)Cl, and a
benzyl radical capable of initiating the polymerization of
monomer through the double bonds (see Scheme 3). This results
in the formation of a polymer chain with pendant groups
consisting of p-benzyl chloride. Also, the polymer has a
double bond at the chain end which can be incorporated into a
growing polymer chain.
Thus, the present invention also concerns a hyperbranched
(co)polymer of the formula:
M1- (M',M2,'M''. and/or
111-(M',M'eM3~ _ . ..i4"a)-( (M1)p-W)q-(t~3)z-...-(M")sJ:-X,
Xti Xi Xj Xk
where M1 is a radically polymerizable monomer having both a
carbon-carbon multiple bond and at least one X group (as
defined above) ; M2, ?=i'. .. up to M" are radically polymerizable
monomers (as defined above); a, b, c... up to d are numbers of
at least zero such that the sum of a, b, c... up to d is at
least 2, preferably at least 3, more preferably at least 4 and
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chain a monomer having a substituent encompassed by the
definition of "X" above.
In the present hyperbranched (co)polymer, the number of
branches will be at most 2'a"11-l, assuming all "X" groups are
active in subsequent ATRP steps. Where, for example, a number
"h" of groups fail to react in subsequent ATRP steps
(e.g., where one of the 1 or 2 C1 groups on a branch in the
octamer shown in Scheme 3 below does not react in subseauent
ATRP s--eps, but the other does), a product of the formula:
M'-(M1aM2,M',...M"d)-t (I"I')p-(M2)a-(t4')_-.. .-(P'1")SJc-h?
X,, X; X X.
is formed. The subsequent number of branches is reduced by 2".
The present invention also concerns cross-linked polymers
and gels, and processes for producing the same. By conducting
the polymerizing step which produces the present branched
andJor hyperbranched (co)polylners for a longer period of time,
gelled polymers may be formed. For example, by increasing the
amount or proportion of p-chloromethyl styrene in the reaction
mixture (e.g., relative to solvent or other monomer(s)), the
cross-link density may be increased and the reaction time may
be lowered.
- 84 -
1 10
Cu (1), bipy
(activauon):
Cu (II) Cl
CIIzCI biPy C11.=
C~-CI12 Clly- C11-CIIT- CI1-CI
Activation f-~~-C11Z C11z C1l--- Cl Activation o 0-
NionorTier X2 11, CII_CI ~
I'lonomcr 0 or dimcr CI o
Cli2C1 C112C1 Cn N
Ln
'T co
cr,
~
~ 6
L.n CIfiCI (D , 1O
Li Acuvation Mononier X4 0 .3
or tctramcr io
Cl tn
Cl 10
cl ~ Clf1-l:Ilj Clt-Cli~ II CIt~C CI W
Cl
C1 ~ c..l 0
Activauon Clli CIIiCI
ci ~ ~ ~
=- ~~ !
Monomer
or n - tncr
C1 C~ CI12C1
11,C1
CI ci r--~ '
Cl ~ -{v)
Cl Cl
CA 02585469 2007-05-03
(Typically, a polymerizing step in any aspect of the
present invention may be conducted for a length of time
sufficient to consume at least 25%, preferably at least
50%,more preferably at least 75%, even more preferably at
least 80% and most preferably at least 90% of monomer.
Alternatively, the present polymerizing step may be conducted
for a length of time sufficient to render the reaction mixture
too viscous to stir, mix or pump with the stirring, mixing or
pumping means being used. However, the polymerizing step rnay
generally be conducted for any desired length of time.)
The present invention also encompasses graft or "comb"
copolymers, prepared by sequential polymerizations. For
example, a first (co)polymer may be prepared by conventional
radical polymerization, then a second (or one or more further)
(co)polymer chains or blocks may be grafted onto the first
(co)polymer by ATRP; a first (co)polymer may be prepared by
ATRP, then one or more further (co)polymer chains or blocks
may be grafted onto the first (co)polymer by conventional
radical polymerization; or the first (co)polymer may be
prepared and the further (co)polymer chains or blocks may be
grafted thereonto by sequential ATRP's.
A combination of ATRP and one or more other
polymerization methods can also be used to prepare different
blocks of a linear or star block copolymer (i.e., when
extending one or several chains from a base (co)polymer).
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Alternatively, a combination of ATRP and one or more other
polymerization methods can be used to prepare a "block
homopolymer", in which distinct blocks of a homopolymer having
one or more different properties (e.g., tacticity) are
prepared by different polymerization processes. Such "block
homopolymers" may exhibit microphase separation.
Thus, the present i-nvention further concerns a method of
preparing a graft or "comb" (co)polymer which includes the
present ATRP process, which may comprise reacting a first
(co)polymer having either a radically transferable X
substituent (as defined above) or a group that is readily
converted (by known chemical methods) into a radically
transferable substituent with a mixture of (i) transition
metal compound capable of participating in a reversible redox
cycle with the first (co)polymer, (ii) a ligand (as defined
above) and (iii) one or more radically polymerizable monomers
(as defined above) to form a reaction mixture containing the
graft or "comb" (co)polymer, then isolating the formed graft
or "comb" (co)polymer from the reaction mixture. The method
may further comprise the step of preparing the first
(co)polymer by conventional radical, anionic, cationic or
metathesis polymerization or by a first ATRP, in which at
least one of the monomers has a R'-R substituent which is
encompassed by the description of the "X" group above. Where
the catalyst andJor initiator used to prepare the first
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(co)polymer (e.g., a Lewis acid used in conventional cationic
polymerization, a conventional metathesis catalyst having a
metal-carbon multiple bond, a conventional organolithium
reagent) may be incompatible with the chosen ATRP
initiation/catalyst system, or may produce an incompatible
intermediate, the process may further comprise the step of
deactivating or removing the catalyst and/or initiator used to
prepare the first (co)polymer prior to the grafting step
(i.e., reacting the first (co)polymer with subseauent
monomer(s) by ATRP).
Alternatively, the method of preparing a graft or "comb"
(co)polymer may comprise preparing a first (co)polymer by the
present ATRP process, then grafting a number of (co)polymer
chains or blocks onto the first (co)polymer by forming the
same number of covalent bonds between the first (co)polymer
and one or more polymerizable monomers (e.g., bv conventional
radical polymerization, conventional anionic polymerization,
conventional cationic polymerization, conventional metathesis
polymerization, or the present ATRP process) polymerizing the
polymerizable monomer(s) in accordance with the conventional
or ATRP processes mentioned to form a reaction mixture
containing the graft or "comb" (co)polymer, then isolating the
formed graft or "comb" (co)polymer from the reaction mixture.
Preferably the X substituent on the first (co)polymer is
Cl or Br. Examples of preferred monomers for the first
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(co)polymer thus include allyl bromide, allyl chloride, vinyl
chloride, 1- or 2- chloropropene, vinyl bromide, 1,1- or 1,2-
dichloro- or dibromoethene, trichloro- or tribromoethylene,
tetrachloro- or tetrabromoethylene, chloroprene, 1-
chlorobutadiene, 1- or 2-bromobutadiene, vinyl chloroacetate,
vinyl dichloroacetate, vinyl trichloroacetate, etc. More
preferred monomers include vinyl chloride, vinyl bromide,
vinyl chloroacetate and chloroprene. It may be necessary or
desirable to hydrogenate (by known methods) the first
(co)polymer (e.g., containing chloroprene units) prior to
grafting by ATRP.
Thus, the present invention also encompasses graft or
"comb" (co)polymers having a formula:
}{t-,.R11 - (M'i-X)
Xf-.Rn- [ (M1iM2j) -X
}tE -eRn - [ (M1iM'iM3k) -XI e
Xz-~R"-( (M1iM2j Wk. . .M"i) -X)
Xe -.R" - [ ( Ml ) P- ( M2 ) q-X ) .
Xf-,R -[ (MI) P_ (M2 ) q- W) z-X~ I
Xt-,.R"- [ (Ml) P- (M2) y- (M') r-. . . - (I''1 ) 9-XJ e
where R" is a first (co)polymer remainder from a first
copolymer having a formula RXf, f> e; e is a number having an
average of at least 2.5, preferably at least 3.0, more
preferably at least 5.0, and most preferably at least 8.0; X
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is as defined above (and is preferably a halogen) ; Ml, 2=12,
t=i',... up to M" are each a radically polymerizable monomer (as
defined above); p, q, r and s are selEcted to provide weight
or number average molecular weights for the corresponding
block is at least 100 g/mol, preferably at least 250 g/mol,
more preferably at least 500 g/mol and even more preferably at
least 1,000 g/mol; and i, j, k... up to 1 represent molar
ratios of the radically polymerizable monomers M', i=i2, M', ...
up to 1=1". The polydispersity, average degree of polymerization
and/or the maximum weight or number average molecular weight
of the (co)polymer or component thereof (e.g., base polymer or
graft side-chain) may be as described above.
Preferred graft copolymers include those in which the
first (co)polymer includes at least three units of vinyl
chloride, vinyl bromide, or a C:-C,-alkenyl halo-C1-C_o-
alkanoate ester (e.g., vinyl chloroacetate). More preferred
graft copolymers include those in which the first (co)polymer
is an N-vinylpyrrolidone/vinyl chloroacetate copolymer
containing on average at least three units of vinyl
chloroacetate per chain, in which polystyrene chains are
grafted thereonto by ATRP using the chloroacetate moiety as
initiator. Such graft copolymers are expected to be useful to
make, e.g., disposable contact lenses.
In the present copolymers, each of the blocks may have a
number average molecular weight in accordance with the
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homopolymers described above. Thus, the present copolymers
may have a molecular weight which corresponds to the number of
blocks (or in the case of star polymers, the number of
branches times the number of blocks) times the number average
molecular weight range for each block.
Polymers and copolymers produced by the present process
have surprisingly low polydispersities for (co)polymers
produced by radical polymerization. Typically, the ratio of
the weight average molecular weight to number average
molecular weight ("Mõ/Mõ") is < 1.5, preferably < 1.4, and can
be as low as 1.10 or less.
Because the "living" (co)polymer chains retain an
initiator fragment in addition to an X or X' as an end group
or as a substituent in the polymer chain, they may be
considered end-functional or in-chain (multi)functional
(co)polymers. Such (co)polymers may be used directly or be
converted to other functional groups for further reactions,
including crosslinking, chain extension, reactive injection
molding (RIM), and preparation of other types of polymers
(such as polyurethanes, polyimides, etc.).
The oresent invention provides the following advantages:
-- A larger number and wider variety of monomers can be
polymerized by radical polymerization, relative to
ionic and other chain polymerizations;
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-- Polymers and copolymers produced by the present
process exhibit a low polydispersity (e.g. , 1=1~/M~, <
1.5, preferably < 1.4, more preferably < 1.25, and
most preferably, < 1.10), thus ensuring a greater
degree of uniformity, control and predictability in
the (co)polymer properties;
-- one can select an initiator which provides an end
group having the same structure as the repeating
polymer units (1-phenylethyl chloride as initiator
and styrene as monomer);
-- The present process provides high conversion of
monomer and high initiator efficiency;
-- The present process exhibits excellent "living"
character, thus facilitating the preparation of
block copolymers which cannot be formed by ionic
processes;
-- Polymers produced by the present process are well-
defined and highly uniform, comparable to polymers
produced by living ionic polymerization;
-- End-functional initiators (e.g., containing CoOH,
OH, NO:, Nõ SCN, etc. , groups) can be used to
provide an end-functional polymer in one pot, and/or
polymer products with different functionalities at
each end (e.g., in addition to one of the above
- 92 -
CA 02585469 2007-05-03
groups at one end, a carbon-carbon double bond,
epoxy, imino, amide, etc., group at another end);
-- The end functionality of the (co)polymers produced
by the present process (e.g., Cl, Br, I, CN, CO2R)
can be easily converted to other functional groups
(e.g., Cl, Br and I can be converted to OH or NH2 by
known processes, CN or COZR can be hydrolyzed to form
a carboxylic acid by known processes, and a
carboxylic acid may be converted by known processes
to a carboxylic acid halide), thus facilitating
their use in chain extension processes (e.g., to
form long-chain polyamides, polyurethar.c= a.~.d/ or
polyesters);
-- In some cases (e.g., where "X" is Cl, Br and I), the
end functionality of the polymers produced by the
present process can be reduced by known inethods to
provide end groups having the same structure as the
repeating polymer units.
-- Even greater improvements can be realized by using
(a) an amount of the corresponding reduced or
oxidized transition metal compound which deactivates
at least part of the free radicals which may
adversely affect polydispersity and molecular weight
control/predictability and/or (b) polymerizing in a
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CA 02585469 2007-05-03
homogeneous system or in the presence of a
solubilized initiating/catalytic system;
-- A wide variety of (co)polymers having various
structures and topologies (e.g., block, random,
graft, alternating, tapered (or "gradient"), star,
"hyperbranched", cross-linked and water-soluble
copolymers and hydrogels) which may have certain
desired properties or a certain desired structure
may be easily synthesized; and
-- Certain such (co)polymers may be prepared using
water as a medium.
Other features of the present invention will become
apparent in the course of the following descriptions of
exemplary embodiments which are given for illustration of the
invention, and are not intended to be limiting thereof.
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EXAMPLES
Example 1:
The effect of air exposure upon heterogeneous ATRP of
styrene. The following amounts of reagents were weighed into
each of three glass tubes under an inert atmosphere in a
nitrogen-filled dry box: 11.0 mg (4.31 x 10'2 mmol) of
[(bipy)CuCl]2 (Kitagawa, S.; Munakata, M. Inorg. Chem. 1981,
20, 2261), 1.00 mL (0.909 g, 8.73 mmol) of dry, deinhibited
styrene, and 6.0 L (6.36 mg, 4.52 x 10'2 mmol) of dry 1-
phenylethylchloride [1-PECl].
The first tube was sealed under vacuum without exposure
to air.
The second tube was uncapped outside of the dry box and
shaken while exposed to ambient atmosphere for two minutes.
The tube was then attached to a vacuum line, the contents were
frozen using liquid nitrogen, the tube was placed under vacuum
for five minutes, the contents were thawed, and then argon was
let into the tube. This "freeze-pump-thaw" procedure was
repeated before the tube was sealed under vacuum, and insured
that dioxygen was removed from the polymerization solution.
The third tube was exposed to ambient atmosphere for 10
minutes and subsequently sealed using the same procedure.
The three tubes were heated at 130 C for 12 h using a
therznostatted oil bath. Afterwards, the individual tubes were
broken, and the contents were dissolved in tetrahydrofuran
[THF] and precipitated into CH3OH. Volatile materials were
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CA 02585469 2007-05-03
removed from the polymer samples under vacuum. Molecular
weights and polydispersities were measured using gel
permeation chromatography [GPC] relative to polystyrene
standards. Results are shown in Table 1 below.
Table 1: Results of the air exposure experiments
Time of Air Yield Mõ PDI
Exposure
None 100 18,200 1.61
2 min 70 13,200 1.59
min 61 11,900 1.39
Examule 2:
General pro=edure for the homogeneous ATRP of styrene.
The following amounts of reagents were weighed into glass
tubes under ambient atmosphere: 12.0 mg (8.37 x 10'2 mmol) of
CuBr, 1.00 mL (0.909 g, 3.73 mmol) of deinhibited styrene, and
12.0 AL (16.3 mg, 3.8 :: 10'2 mmol) of '_-phenylethylbromide [1-
PEBr3. For polymerizations using dNbipy, 72.0 mg (0.175 mmol)
of the ligand was added, for dTbipy, :7.0 mg (0.175 mmol) was
added, and for dHbipy, 62.0 mg (0.175 mmol) was added. Two
"freeze-pump-thaw', cycles (described above) were performed on
the contents of each tube in order to insure that dioxygen was
removed from the polymerization solution. Each tube was
sealed under vacuum.
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The tubes were placed in an oil bath thermostatted at 100
C. At timed intervals, the tubes were removed from the oil
bath and cooled to 0 C using an ice bath in order to quench
the polymerization. Afterwards, the individual tubes were
broken, and the contents were dissolved in 10.0 ml of THF.
Catalyst could be removed by passing the polymer solution
through an activated alumina column. Percent conversion of
each sample was measured using gas chromatography, and
molecular weights and polydispersities were measured using GPC
relative to polystyrene standards. Results are shown in
Tables 2 and 3 below.
Table 2: Molecular weight data for the homogeneous ATRP of
styrene using dTbipy as the ligand.
Time (min) Mr, (GPC) PDI (GPC)
conversion
60 14.5 1250 1.08
120 20 1610 1.09
181 28 2650 1.09
270 43 3880 1.08
303 49 4670 1.10
438 59 5700 1.08
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Table 3: Molecular weiaht data_for the homogeneous ATRP of
styrene using dHbipy as the ligand.
Time (min) % Mõ (GPC) PDI (GPC)
Conversion
60 31 2860 1.05
124 45 3710 1.04
180 58 6390 1.04
240 78 8780 1.05
390 90 9230 1.06
Examole 3:
General procedures for the determination of the effect of
added copper(II) on homogeneous ATRP of styrene. dHbipy was
prepared according to the procedure of Kramer et al (Angew.
Chem., Intl. Ed. E'ngl. 1993, 32, 703). dTbipy was prepared
according to the procedure of Hadda and Bozec (Polyhedron
1988, 7, 575). CuCI was purified according to the procedure
of Keller and S=lycoff (Inorg. Synth. 1946, 2, 1)
Method 1: Weighed addition of the transition metal
reagents
In a dry box, appropriate amounts of pure CuCl, pure
CuClZ, bipyridyl ligand, dry 1-PEC1 and 1,4-dimethoxybenzene
added to a 100 mL Schlenk flask equipped with a magnetic stir
bar. The flask was fitted with a rubber septum, removed from
the dry box, and attached to a Schlenk line. The appropriate
amounts of dry, deinhibited styrene and high boiling solvent
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were added to the flask, and ths septum was fixed in place
using copper wire. The flask, with the polymerization
solution always under an argon atmosphere, was heated at 130
C using a thermostatted oil bath, and upon heating a
homogeneous red-brown solution formed. Aliquots of the
polymerization solution (2.00 mL) were removed at timed
intervals using a purged syringe and dissolved in 10.0 ml of
THF. Percent conversion of each sample was measured using gas
chromatography, and molecular weights and polydispersities
were measured using GPC relative to polystyrene standards.
Polymerization #1 (no CuClz):
8.5 mg (0.86 mmol) of CuCl
0.120 mL (0.91 mmol) of 1-PEC1
46.6 mg (1.74 mmol) of dTbipy
20.0 mL (0.175 mol) of styrene
20.0 g of p-dimethoxybenzene
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Table 4: Results_of polymerization #1
Time (min) % r1, (GPC) PDI (GPC)
Conversion
38 12 2,910 1.60
82 19 3,700 1.60
120 23 5,370 1.57
177 46 8,480 1.46
242 58 11,500 1.37
306 66 13,300 1.33
373 69 14,400 1.29
1318 93 19,000 1.22
Polymerization #2 (3 mol % CuCl,):
8.9 mg (0.90 mmol) of CuCl
0.4 mg (0.03 mmol) of CuCl,
0.120 mL (0.91 mmol) of 1-PEC1
47.1 mg (1.75 mmol) of dTbipy
20.0 mL (0.175 mol) of styrene
20.0 g of p-dimethoxybenzene
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Table 5: Results of polymerization #2
Time (min) % Mõ (GPC) PDI (GPC)
Conversion
37 0 0 --
85 8 1,870 1.44
123 22.5 3,280 1:41
194 30.5 4,470 1.40
256 39 6,920 1.31
312 43 9,340 1.27
381 48 10,000 1.25
1321 79 15,490 1.21
1762 83 15,300 1.21
Method 2: Addition of stock solutions of the copper
reagents
The polymerizations were conducted as in the general
procedure for the homogeneous ATRP of styrene, except that
stock solutions of the dipyridyl ligand with CuBr, and
separately, CuBr2 in styrene were prepared and added to 1-PEBr
in the glass tube before removal from the dry box and sealing.
Polymerization #1 (no CuBr2):
4.5 x 10-2 mmol of CuBr
6.2 L (4.5 x 10'2 mmol) of 1-PEBr
32.0 mg (9.0 x 10'2 mmol) of dHbipy
0.5 mL (4.36 mol) of styrene
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Table 6: Results of polymerization #1
Time (min) 1=tn (GPC) PDI (GPC)
Conversion
70 38 4,510 1.08
120 64 6,460 1.09
160 68 6,710 1.10
200 72 8,290 1.;1
240 82 9,480 1.14
300 86 10,180 1.13
Polymerization T 2 (1.0 mol 'o- of CuBr, )
4.5 x 10'2 mmol of CuBr
4.5 x 10'a mmol of CuBr,
6.2 L (4.5 x 10'2 mmol) of 1-PEBr
9.0 x 10-1 mmol of dHbipy
0.5 mL (4.36 mol) of styrene
Table 7: Results of polymerization #2
Time (min) % Mõ (GPC) PDI (GPC)
Conversion
50 5 1210 1.07
105 18 2870 1.05
165 39 4950 1.06
174 40 4990 1.06
300 68 6470 1.07
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CA 02585469 2007-05-03
Examnle 4: ATRP of water-soluble monomers
General procedure for the polymerization of water soluble
monomers. Under ambient conditions, a glass tube was charged
with the appropriate amounts of copper(I) halide (unpurified),
bipy, initiator, and monomer. Water, if used, was then added.
Two "freeze-pump-thaw" cycles (described above) were,performed
on the contents of each tube in order to insure that dioxygen
was removed from the polymerization solution. Each tube was
sealed under vacuum, and then placed in a thermostatted oil
bath at 80 C or 100 C for 12 h. Afterwards, the individual
tubes were broken.
(a) P(NVP). For N-vinyl pyrrolidone, the contents were
dissolved in 10.0 ml of THF. Percent conversion of each
sample was measured using gas chromatography.
Bulk conditions:
12.1 mg (8.4 x 10'2 mmol) of CuBr
28.1 mg (0.18 mmol) of bipy
4.0 l (6.2 mg, 4.1 x 10"2 mmol) of bromomethyl acetate
1.00 mL (0.980 g, 8.82 mmol) of N-vinyl pyrrolidone
Heated at l00 C for 12 h
t Conversion = 100
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Aqueous conditions:
13.7 mg (9.6 x 10' mmol) of CuBr
30.1 mg (0.19 mmol) of bipy
4.0 l (6.2 mg, 4.1 x 10-2 mmol) of bromomethyl acetate
1.00 mL (0.980 g, 8.82 mmol) of f1-vinyl oyrrolidone
1.00 mL of water
Heated at 100 C for 12 h
% Conversion = 80
(b) ?(acrylamide), For acrylamide, the contents were
dissolved in 50 mL of water and precipitated into 200 mL of
CH30H. The polymer was isolated bv filtration, and volatile
materials were removed under vacuum.
Conditions:
10.7 mg (7.5 x 10'2 mmol ) of CuBr
39.3 ma (0.25 mmol) of bipy
8.0 41 (12.0 mg, 7.2 x 10'2 mmol) of inethvl-2-
bromopropionate
1.018 g (14.3 mmol) of acrylamide
1.00 mL of water
Heated at 100 C for 12 h.
Yield: 0.325 (32 %) of a white solid
(c) P(HEMA). For 2-hydroxyethyl methacrylate, the
contents were dissolved in 50 mL of dimethyl formamide [DMF]
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and precipitated into 200 mL of diethyl ether. The.solvent
was decanted from the oily solid, and the residue was
dissolved in 25 mL of DMF. To this solution, 25 mL of acetyl
chloride was added and the solution was heated at reflux for 4
h. Then, 50 mL of THF was added and the solution was poured
into 250 mL of CH3OH. The resulting suspension was- isolated by
centrifugation, and the material was repreciptated from 50 mL
of THF using 250 mL of CH0OH. The molecular weight and
polydispersity of the sample was measured using GPC relative
to polystyrene standards.
Conditions:
11.1 mg (2.1 x 10"2 mol) of Cu (bipy) 2' (PF6) "
6.0 l (8.0 mg, 4.1 x 10"2 mmol) of ethyl-2-
bromoisobutyrate
1.00 mL (1.07 g, 5.5 mmol) of 2-hydroxyethyl methacrylate
1.00 mL of water
Heated at 80 C for 12 h.
Mn = 17,400; PDI = 1.60
Examples 5-8: Random copolymers
ATRP allows preparation of random copolymers of a variety
of monomers providing a broad range of compositions, well
controlled molecular weights and narrow molecular weight
distributions.
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Examole 5: Preparation of random copolymers of methyl
methacrylate and styrene
(a) Copolymers containing 20% styrene
0.007 g of CuBr, 0.0089 g of 2,2'-bipyridyl and 0.067 ml
of ethyl-2-bromoisobutyrate was added to a degassed mixture of
styrene (0.25 ml) and methyl methacrylate (0.75 ml) and the
reaction mixture was heated to 100 C. After 2.5 hrs. the
polymerization was interrupted, and the resulting polymer was
precipitated on methanol and purified by reprecipitation from
THF/methanol. The yield of the copolymer was 35%.
The composition of the copolymer was determined by NMR to
be 20 mol. o styrene. Molecular weight, M.,, of the copolymer
was 11,000 and polydispersity (Mw/Mn) = 1.25, as obtained from
GPC relative to polystyrene standards.
(b) Copolymers containing 50% styrene
0.007 g of CuBr, 0.0089 q of 2,2'-bipyridyl and 0.067 ml
of ethyl-2-bromoisobutyrate was added to a degassed mixture of
styrene (0.5 ml) and methyl methacrylate (0.5 ml). The
reaction mixture was heated to 100 C. After 3.5 hrs., the
polymerization was interrupted, and the resulting polymer was
precipitated in methanol and purified by reprecipitation from
THF/methanol. The yield of the copolymer was 18%.
The composition of the copolymer was determined by NMR to
be 50% (by moles) of styrene. Molecular weight, Mrõ of the
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copolymer was 9,000 and polydispersity Mw/Mn = 1.27, as
obtained from GPC relative to polystyrene standards.
(c) Copolymers containing 65% styrene
0.007 g of CuBr, 0.0089 g of 2,2'-bipyridyl and0.067 ml
of ethyl-2-bromoisobutyrate was added to a degassed mixture of
styrene (0.75 ml) and methyl methacrylate (0.25 ml). The
reaction mixture was heated to 100 C. After 2.0 hrs., the
polymerization was interrupted, and the resulting polymer was
precipitated in methanol and purified by reprecipitation from
THF/methanol. The yield of the copolymer was 16%.
The composition of the copolymer was determined by NMR to
be 65% (by moles) of styrene. Molecular weight, M,, of the
copolymer was 6,000 and polydispersity Mw/Mn = 1.25, as
obtained from GPC relative to polystyrene standards.
Example 6: Random Copolymerization Between Styrene (70 mol%)
and Acrylonitrile (30 mol%)
2,2'-Bipyridyl (0.1781 g), dimethoxybenzene (20 g), and
Cu(I) Cl (0.0376 g) were added to a 100 ml flask, which was
sealed with a rubber septum and copper wire. The flask was
placed under vacuum and then back-filled with argon. This was
repeated two more times. Styrene (17.2 ml) and acrylonitrile
(4.2 ml) were then added via syringe. The monomers had been
previously deinhibited by passing through a column of alumina
and degassed by bubbling argon through the monomer for fifteen
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minutes. 1-Phenylethyl chloride (0.0534 g) was then added to
the reaction mixture by syringe, and the reaction was heated
to 130 C. Samples were taken (0.5 ml each). Conversion was
determined by 1H NMR, and the Mn and polydispersity (PD)
determined by GPC. The samples were then purified by
dissolution in THF and precipitation into methanol three
times. The purified polymer was then evaluated for
acrylonitrile content by 'H NMR. The differences in monomer
reactivities (reactivity ratio) may provide a compositional
gradient. Table 8 lists the results.
Table 8
Time (h) Conversion (o) M. PD o Acrylonitrile
2.0 27.0 8160 1.65 54.2
5.25 29.6 9797 1.51 35.6
8.0 39.4 11131 1.44 40.8
21.0 53.6 16248 1.31 34.1
Example 7: Preparation of random copolymer of styrene and
methyl acrylate
0.010 g of CuBr, 0.0322 g of 2,2'-bipyridyl and 0.010 ml
of ethyl-2-bromoisobutyrate was added to a degassed mixture of
methyl acrylate (0.42 ml) and styrene (1.00 ml) and the
reaction mixture was heated to 90 C. After 14 hrs., the
polymerization was interrupted and the resulting polymer was
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precipitated on methanol and purified by reprecipitation from
THF/methanol. The yield of the copolymer was 87%.
The composition of the copolymer was determined by NMR to
be 40% (by moles) of styrene. Molecular weight, M, of the
copolymer was 22,000 and polydispersity Mw/Mn = 1.18, as
obtained from GPC relative to polystyrene standards: The
monomer reactivity ratio may have provided a compositional
gradient.
Example 8: Preparation of random copolymer of methyl
methacrylate and butyl acrylate
0.010 g of CuBr, 0.0322 g of 2,2'-bipyridyl and 0.010 ml
of ethyl-2-bromoisobutyrate was added to a degassed mixture of
methyl methacrylate (2.5 ml) and butyl acrylate (2.5 ml) and
the reaction mixture was heated to 110 C. After 2.5 hrs., the
polymerization was interrupted, and the resulting polymer was
precipitated on methanol and purified by reprecipitation from
THF/methanol. The yield of the copolymer was 53%.
The composition of the copolymer was determined by NMR to
be 15% (by moles) of butyl acrylate. Molecular weight, Mr, of
the copolymer was 11,000 and polydispersity Mw/Mn = 1.50, as
obtained from GPC relative to polystyrene standards. The
monomer reactivity ratio may have provided a compositional
gradient.
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Alternating and Partially Alternatina Copolymers
Examnle 9: Alternating copolymers isobutylene (IB) /methyl
acrylate (molar feed 3.5:1)
To 0.11 g (6.68 x 10'4 mole) 2,2'-bipyridyl and 0.036 g
(2.34 x 10'' mole) CuBr at -30 C in a glass tube, were added
1.75 ml (2 x 10'2 mole) IB, 0.5 ml (0.55 x 10'2 mole) methyl
acrylate (MA) and 0.036 ml (2.34 x 10"4 mole) 1-phenylethyl
bromide under an argon atmosphere. The glass tube was sealed
under vacuum, and the reaction mixture was warmed at 50 C for
48 hours. The reaction mixture was then dissolved in THF, and
conversion of MA as determined by GC was 100%. The polymer
was then precipitated in methanol (three times), filtered,
dried at 60 C under vacuum for 48 h and weighed. The content
of IB in copolymer was 51%, and ri~ = 4050, 2I,/Mr, = 1.46 (t4th =
3400). The % of IB in the copolymer as determined by
integration of inethoxy and gem-dimethyl regions of the 'H-NMR
spectrum was 44%. The tacticitv of the alternating copolymer
as calculated from the signals of inethoxy protons according to
the method described by Kuntz (J. Polym. Sci. Polym. Chein. 16,
1747, 1978) is rr/mr/mm = 46/28/26. The glass transition
temperature of product as determined by DSC was -28 C.
Example 10: IB/MA Copolymer (molar feed 1:1)
To 0.055 g (3.5 x 10'4 mole) 2,2'-bipyridyl and 0.017 g
(1.17 x 10"4 mole) CuBr at -30 C in a glass tube, were added
0.5 ml (0.55 x 10'2 mole) IB, 0.5 ml (0.55 x 10"2 mole) methyl
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acrylate and Ø016 ml (1.17 x_10'4 mole) 1-phenylethyl bromide
under argon atmosphere. The glass tube was sealed under
vacuum and the reaction mixture was warmed at 50 C for 24
hours. The reaction mixture was then dissolved in THF, and
conversion of MA as determined by GC was 100%. The polymer
was than precipitated in methanol (three times), filtered,
dried at 60 C under vacuum for 48 h and weighed. The content
of IB in copolymer was 28% and Mn = 6400, M4JMn = 1.52 (Ml,, =
6500). The a of IB in copolymer determined by integration of
methoxy and gem-dimethyl region of the =H-NMR spectrum
according to the method described by Kuntz was 26%. The glass
transition temperature of the product as determined by DSC was
-24 C.
Example 11: IB/MA Copolymer (molar feed 1:3)
To 0.11 g (6.68 x 10"1 mole) 2,2'-bipyridyl and 0.036 g
(2.34 x 10"' mole) CuBr at -30 C in a glass tube, were added
0.5 ml (0.55 x 10"2 mole) IB, 1.5 ml (1.65 x 10'2 molz) methyl
acrylate and 0.036 ml (2.34 x 10'4 mole) 1-phenylethyl bromide
under argon atmosphere. The glass tube was sealed under
vacuum and the reaction mixture warmed at 50 C for 48 hours.
The reaction mixture was then dissolved in THF, and the
conversion of MA as determined by GC was 100%. The polymer
was then precipitated in methanol (three times), filtered,
dried at 60 C under vacuum for 48 h and weighed. The content
of IB in the copolymer was 25%, and Mn = 7570, Mõ/Mõ = 1.58 (Mth
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= 7400). The % of IB in copolymer as determined by
integration of inethoxy and gem-dimethyl region of the 1H-NMR
spectrum according to the method described by Kuntz was 24%.
The glass transition temperature of the product as determined
by DSC was -15 C.
Example 12: Alternating copolymers of isobutyl vinyl ether
(IBVE)/methyl acrylate (1:1)
To 0.055 g(3.51 10-4 mole) 2,2'-bipyridyl and 0.017 g
(1.17 x 10"a mole) CuBr in a glass -zube, were added 0.6 ml
(0.55 x 10'' mole) IBVE, 0.5 ml (0.55 x 10-z mole) methyl
acrylate and 0.017 ml (1.17 x 10"4 mole) 1-phenylethyl bromide
under argon atmosphere. The glass tube was sealed under
vacuum, and the reaction mixture was warmed at 50 C for 12
hours. The reaction mixture was then dissolved in TIHF, and
the conversion of 1=Lk and IBVE as determined by GC were 100%.
The polymer was then precipitated in methanol (three times),
filtered, dried at 60 C under vacuum for 48 h and weighed.
The content of IBVE in copolymer was 51%, and 1.1, = 8110, Mõ/Mõ
= 1.54 (ri:h = 8700). The glass transition temperature of the
product as determined by DSC was -31.3 C.
Example 13: Copolymers of isobutyl vinyl ether/methyl
acrylate (3:1)
To 0.11 g(6.68 x 10"4 mole) 2,2'-bipyridyl and 0.036 g
(2.34 x 10'4 male) CuBr in a glass tube, were added 1.8 ml
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(1.65 x 10-2 mole) IBVE, 0.5 ml (0.55 x 10'2 mole) methyl
acrylate and 0.034 ml (2.34 x 10'4 mole) 1-phenylethyl bromide
under argon atmosphere. The glass tube was sealed under
vacuum, and the reaction mixture was warmed at 50 C for 12
hours. The reaction mixture was then dissolved in THF, and
the conversion of MA and IBVE as determined by GC were 100t.
The polymer was then precipitated in methanol (three times),
filtered, dried at 60 C under vacuum for 48 h and weighed.
The content of IBVE in the copolymer was 75%, and Mn = 8710,
Mõ/14., = 2.00 (Mth = 9090) . The glass transition temperatures of
the product as determined by DSC were -44.3 C and 7.1 C.
Example 14: Copolymers of isobutyl vinyl ether/methyl
acrylate (1:3)
To 0.11 g (6.68 x 10'' mole) 2,2'-bipyridyl and 0.036 g
(2.34 x 10'4 mole) CuBr in a glass tube, were added 0.6 ml
(0.55 x 10"2 mole) IBVE, 1.5 ml (1.65 x 10"2 mole) methyl
acrylate and 0.034 ml (2.34 x 10'' mole) 1-phenylethyl bromide
under argon atmosphere. The glass tube was sealed under
vacuum, and the reaction mixture was warmed at 50 C for 12
hours. The reaction mixture was then dissolved in THF, and
the conversion of MA and IBVE as determined by GC were 100%.
The polymer was then precipitated in methanol (three times),
filtered, dried at 60 C under vacuum for 48 h and weighed.
The content of IBVE in the copolymer was 25%, and Mn = 7860,
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M,,,/ri' = 1.90 (t=it, = 8400) . The glass transition temperatures of
the product as determined by DSC were at -31.0 C and 5.6 C.
Periodic Copolymers
Examnle 15:
Under an argon atmosphere, 11.1 mL of styrene (9.6 x 10-2
mole) was added to 0.097g (6 x 10'4 mole) of 2,2'-bipyridyl and
0.020 g(2 x 10-4 mole) CuCl in a 50 mL glass flask. The
initiator 0.030 mL (2 x 10'a mole) 1-phenvlethyl chloride was
then added via svringe. The flask was then immersed in oil
bath at 130 C. At various time intervals, samples from the
reaction mixture were transferred to an 2dMR tube, and the
conversion of styrene was determined.
Thereafter, 1.5 eq. of maleic anhydride (0.03 g, 3 x 10'4
mole) in benzene (4 mL) was injected into the flask at times
of 20, 40, 60 and 80% conversion of styrene. After 25 hours,
the reaction mixture was cooled to room temperature, and 15 mL
of THF was added to the samples to dissolve the polymers. The
conversion of styrene by measuring residual inonomer was 95%.
The polymer was precipitated in dry hexane, filtered,
dried at 60 C under vacuum for 48 h and weighed. The product
had a Mr, = 47500 and Mw/Mt, = 1.12 (Mth = 50, 000) . The content
of maleic anhydride was determined by IR spectroscopy, and
corresponded to the introduced amount.
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Gradient Gopolymers
Example 16: Preparation of a methyl acrylate/methyl
methacrylate gradient copolymer
0.029 g of CuBr, 0.096 g of 2,2'-bipyridyl and 0.030 ml
of ethyl-2-bromoisobutyrate were added to a degassed solution
of methyl acrylate (2.5 ml) and methyl methacrylate (2.0 ml)
in ethyl acetate (2.0 ml). The reaction mixture was
thermostated at 90 C and samples were withdrawn after 3.0 hr,
hr, 7 hr and 23 hr. From the composition data obtained from
NMR measurements of these samples and from molecular weights
evaluation from GPC measurements relative to polystyrene
standards, the compositional gradient along the chain of the
final copolymer was calculated (Fig. 3A-B). The final polymer
(at 96% conversion) was purified by reprecipitation from
methanol/THF.
Example 17:
0.125 g of CuBr, 0.407 g of 2,2'-bipyridyl and 0.118 ml
of ethyl-2-bromoisobutyrate was added to a degassed mixture of
methyl acrylate (3.8 ml) and methyl methacrylate (4.8 ml).
The reaction mixture was thermostated at 80 C and samples were
withdrawn after 0.5 hr, 1 hr and 1.5 hr. From the composition
data obtained from NMR measurements of these samples and from
molecular weights evaluation from GPC measurements relative to
polystyrene standards, the compositional gradient along the
chain of the final copolymer was calculated (Fig. 4A-B). The
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final polymer (at 88% conv.) was purified by reprecipitation
from methanol/THF.
Exattiple l8: Preparation of a styrene/methyl methacrylate
gradient copolymer
0.063 g of CuBr, 0.205 g of 2,2'-bipyridyl and 0.064 ml
of ethyl-2-bromoisobutyrate was added to 5 ml of styrene and
the mixture was heated at 110 C. A mixture of styrene (5 ml)
and methyl methacrylate (5 ml) was added at a rate of addition
of 0.1 ml/min, followed by 10 ml of methyl methacrylate added
at the same rate. Samples were withdrawn at certain time
periods, and from the composition data obtained from NMR
measurements of these samples and from GPC measurement of the
molecular weights relative to polystyrene standards, the
compositional gradient along the chain of the final copolymer
was calculated (Fig. 5A-B). The final polymer (2.34 g) was
purified by reprecipitation from methanol/THF. DSC
measurements of the final copolymer show a single glass
transition with T. = 106 C.
Example 19: Preparation of methyl acrylate/methyl
methacrylate gradient copolymer
0.107 g of CuBr, 0.349 g of 2,2'-bipyridyl and 0.109 ml
of ethyl-2-bromoisobutyrate was added to a mixture of methyl
acrylate (5 ml) and methyl methacrylate (10 ml), and the
reaction mixture was heated to 90 C. Methyl acrylate (20 ml)
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was added to the reaction mixture at a rate of addition of 0.1
ml/min. Samples were withdrawn at certain time periods, and
from the composition data obtained from NMR measurements of
these samples and from GPC measurement of the molecular
weights relative to polystyrene standards, the compositional
gradient along the chain of the final copolymer was calculated
(Fig. 6A-B). The final polymer (3.15 g) was purified by
reprecipitation from methanol/THF. DSC measurements of the
final copolymer show a single glass transition with T. = 52 C.
ExamAle 20: Preparation of inethyl acrylate/styrene gradient
copolymers with varying gradient of composition
0.063 g of CuBr, 0.205 g of 2,21-bipyridyl and 0.64 ml of
ethyl-2-bromoisobutyrate was added to 10 ml of styrene and the
reaction mixture was heated to 95 C. Methyl acrylate was
added to the reaction mixture at a rate of addition of 0.1
ml/min such that the final reaction mixture contained 90% of
methyl methacrylate. Samples were withdrawn at certain time
periods and from the composition data obtained from NMR
measurements of these samples and from GPC measurement of the
molecular weights relative to polystyrene standards, the
compositional gradient along the chain of the final copolymer
was calculated (Fig. 7A-B). The final polymer (1.98 g) was
purified by reprecipitation from methanol/THF. DSC
measurements of the final copolymer show a single glass
transition with T. = 58 C.
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In a separate experiment, 0.063 g of CuBr, 0.205 g of
2,2'-bipyridyl and 0.64 ml of ethyl-2-bromoisobutyrate was
added to 10 ml of styrene and the reaction mixture was heated
to 95 C. Methyl acrylate was added to the reaction mixture at
a rate of addition of 0.085 ml/min such that the final
reaction mixture contained 90% of methyl methacrylate.
Samples were withdrawn at certain time periods. From the
composition data obtained from NMR measurements of these
samAles and from GPC measurement of the molecular weights
relative to polystyrene standards, the compositional gradient
along the chain of the final copolymer was calculated (Fig.
8A-B). The final polymer (1.94g) was purified by
reprecipitation from methanol/THF. DSC measurements of the
final copolymer show a single glass transition with T. = 72 C.
In a third experiment, 0.063 g of CuBr, 0.205 g of 2,2'-
bipyridyl and 0.64 ml of ethyl-2-bromoisobutyrate was added to
ml of styrene and the reaction mixture was heated to 95 C.
Methyl acrylate was added to the reaction mixture at a rate of
addition of 0.05 ml/min such that the final reaction mixture
contained 90% of methyl methacrylate. Samples were withdrawn
at certain time periods. From the composition data obtained
from N:At measurements of these samples and from GPC
measurement of the molecular weights relative to polystyrene
standards, the compositional gradient along the chain of the
final copolymer was calculated (Fig. 9A-B). The final polymer
(3.08 g) was purified by reprecipitation from methanol/THF.
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DSC measurements of the final copolymer show a single glass
transition with T. = 58 C.
Example 21: Branched and Hyperbranched Polymers
Homopolymerizations were performed as follows:
Typically, p-chloromethylstyrene, p-CMS, was polymerized in
the presence of CuCl (1% relative to PCS) and 2,2'-bipyridyl
(3%), at 110 C, under oxygen free conditions, i.e., argon
atmosphere. p-Chloromethylstyrene was added to a flask
containing CuCl/bipyridyl. Immediately upon addition of p-
CMS, a deep red, slightly heterogeneous solution was obtained.
Heating resulted in the color of the solution changing from
red to green within fifteen minutes of heating.
After a period of time the reaction was stopped and the
sample dissolved in THF. Conversion was determined by 'H NMR,
and was found to be greater than 80%. The samples showed
almost no observable change in viscosity at the reaction
temperature, but cooling to room temperature resulted in the
sample becoming solid. The green copper(II) material was
removed by passing the mixture through a column of alumina.
Unprecipitated samples were analyzed by GPC relative to
polystyrene standards. The polymer was then purified by
precipitation into methanol from THF. These samples were then
analyzed by 'H NMR to determine molecular weight. Table 9
outlines experimental results. All yields were > 70 %.
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Table 9: Homopolymerization of p-Chloromethylstyrene
in the Presence of Cu (I) and 2,2'-Bipyridyla
Temperature Time (h) I Conversion Mõ'' M71 M,,,/Mõc Mnf
' ( -%)'
125 C 0.5 67 1900 1160 1.8 1070
" 1.0 75 2250 1780 2.1 1870
" 1.5 90 2940 2410 2.1 2480
" 2.0 92 6280 2510 2.5 2750
110 C 24.0 96 2420 2100 1.3 ---
a) Bulk polymerization, [M]O = 7.04 1.1, [CuCl] = 0.07 M,
[bipy] = 0.21 M.
b) Solution polymerization in benzene, [M] = 3.52 t=i, [CuCl]
= 0.035 1.1, [bipy]. = 0.11 M.
c) Conversion based on consumption of double bonds.
d) M}, determined by 'H NMR after precipitation.
e) M, i=% determined of entire sample, prior to
precipitation, by GPC, using linear polystyrene
standards.
f) Mn by GPC, using linear polystvrene standards, after
precipitation into methanol/brine.
Copolymerizations were carried out as follows: Styrene
(18.18 g, 20 ml) was polymerized in a 50% w/v solution using
p-dimethoxybenzene (20 g) as solvent. The amount of p-
chloromethylstyrene was 20 (0.4 ml). The molar ratio of p-
chloromethylstyrene/CuCl (0.2594 5)/2,2'-bipyridyl (1.287 g)
was 1:1:3. The solids were placed in a flask with a rubber
septum and magnetic stirrer, and degassed three times by
vacuum and back filling with argon. Degassed monomer was
added via syringe. The appropriate amount of p-chloromethyl-
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styrene was then added via syringe. The reaction was heated
to 130 C. The reaction was quenched by precipitation into
methanol. After 15 hours, conversion was 94.3% as determined
by 'H NMR. Yield was 76%.
The sample was evaluated by SEC using relative
calibration, and found to have Mn = 13400 and M, = 75000. By
universal calibration, in conjunction with light scattering,
the Mn = 31,600 and M, = 164,500.
Methyl methacrylate (20 ml, 18.72 g) was used in place of
styrene. The reaction was run for 2 hours at 100 C. M",sEC
44,700 and M%,,sEc = 112,400. M, = 58,700 (universal
calibration), M,,, = 141,200 (light scattering).
Cross-Linked Polymers and Gels
Example 22:
Styrene (9.09 g, 10 ml) was polymerized in a 50 0
(w/vol.) solution using p-dimethoxybenzene (10 g) as solvent.
The amount of p-chloromethylstyrene was 2% (0.2 ml). The
molar ratio of p-chloromethylstyrene/CuCl (0.1297 g)/2,2'-
bipyridyl (0.6453 g) was 1:1:3. The solids were placed in a
flask with a rubber septum and magnetic stirrer, and degassed
three times by vacuum and back filling with argon. Degassed
monomer was added via syringe. p-Chloromethylstyrene was then
added via syringe. The reaction was heated to 130 C. The
reaction was quenched by precipitation into methanol. After
64.5 hours, conversion was 94.3% as determined by 1H N241t.
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Yield was 90%. A cloudy polymer solution was made in THF, but
could not be passed through a 0.45 micron PTFE filter. Upon
placing the solution in a centrifuge for 26 hours at 7000 rpm,
the solution was clear with a slight layer of solid material
at the bottom of the vial. The solution was passed through a
0.45 micron PTFE filter. M., = 118, 000, 1-1õ/M., = 3.74.
Example 23:
Styrene (9.09 g, 10 ml) was polymerized in a 50% (w/vol.)
solution using p-dimethoxvbenzene (l0 g) as solvent. The
amount of p-CMS was 10% (0.2 ml). The molar ratio of p-CMS/
CuCl (0.1297 g)/2,2'-bipyridyl (0.6453 g) was 1:1:3. The
solids were placed in a flask with a rubber septum and
magnetic stirrer, and degassed three times by vacuum and back
filling with argon. Degassed monomer was added via syringe.
p-Chloromethyl stvrene was then added via syringe. The
reaction was heated to 130 C. The reaction was auenched by
precipitation into methanol. After 24 hours, conversion was
94.3% as determined by 'H NMR. Yield was > 90%. The polymer
was stirred in THF but could not be dissolved. The polymer
sample was placed in a soxhlet apparatus under refluxing THF
to remove copper salts.
The obtained sample was placed in THF and allowed to come
to equilibrium. The gel was determined to have an equilibrium
THF content of 89%.
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Example 24: Difunctional Polymers
Polystyrene with two bromine or azide end groups were
synthesized.
jLI o,W-Dibromonolystyrene:
Styrene (18.18 g, 20 ml) was polymerized in a 50 0
(w/vol.) solution using p-dimethoxybenzene (20 g) as solvent.
a,e'-Dibromo-p-xylene (1.848 g) was used as the initiator.
The molar ratio of a,a'-Dibromo-p-xylene/styrene/CuBr (1.00
g)/2,2'-bipyridyl (3.28 g) was 1:1:3. The solids were placed
in a flask with a rubber saptum and magnetic stirrer, and
degassed three times by vacuum and back filling with argon.
Degassed monomer was added via syringe. The reaction was
heated to 110 C. After 5.5 hours conversion was > 95% as
determined by 1H NMR. The reaction was quenched by
precipitation into methanol. Yield was > 90%. The polymer
was redissolved in THF and precipitated into methanol three
times. The polymer sample was dried under vacuum at room
temperature overnight. Mn, as determined by comparison of the
methine protons adjacent to bromine and the aliphatic protons,
was 2340. SEC, Mn = 2440.
B,L a , w-Diaz idopolVstyrene :
A sample of=the above c,w-dibromopolystyrene (5.0 g) was
dissolved in dry THF (20 ml) in the presence of tetrabutyl
ammonium fluoride (1 mmol F"/g) on silica gel (6.15 g).
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Trimethylsilyl azide (0.706 g, 0.81 ml) was then added via
syringe. The solution was stirred for 16 hours under argon.
H Nt4R showed complete conversion of the methine protons
adjacent to bromine to being adjacent to N. M.,, by 'H NMR,
was 2340. Infrared spectroscopy showed a peak at 2080 cm-1,
which corresponds to the azide functional group.
A sample of the e,w-diazidopolystyrene (4.7 mg) was
placed in a DSC sample pan and was heated to 250 C and held
for 15 minutes. A series of endo and exothermic neaks were
seen starting at 215 C. The sample was allowed to cool and
then dissolved in THF. The solution was injected into a SEC
instrument. The I=in was 6500, a 250% increase in molecular
weight. The distribution was broad, however.
Examnle 25: Water Swellable Polymers
(A): NVPlVAc-C1 Polymer:
N-vinylpyrrolidinone (50 ml, 48.07 g), vinyl
chloroacetate (0.26 g, 0.25 ml), and AIBN (0.7102 g) were
combined in a 300 ml three-neck, round-bottom flask. The
monomers were degassed by bubbling argon through the mixture.
The mixture was heated to 60 C for 1 h. The resulting solid
polymer was allowed to cool and then dissolved in THF. The
solution was precipitated into hexanes, and the resulting
polymer filtered and dried at 70 C under vacuum for three
days.
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(B): Hydrogel A: -
The NVP/VAc-Cl polymer (5.0 g) of Example 25(A) was
dissolved in styrene (20 ml), in the presence of CuCl (0.0411
g) and 4,4'-di-t-butyl-2, 2'-bipyridyl (0.2224 g), under
oxygen free conditions. The reaction mixture was heated to
130 C. After 30 minutes, the reaction mixture became
gelatinous. The mixture was dissolved in DMF and precipitated
into water. A gel-like mass was obtained and filtered. The
resulting solid was a gel weighing 20.0 g. The gel was dried
over P2O5 at 70 C under vacuum for 2.5 days. Yield 4.0 g.
(C): HVdroaelB=
The 11VD/VAc-C1 polymer (5.0 g) of Example 25(A) was
dissolved in styrene (20 ml), in the presence of CuCl (0.0041
g) and 4,4'-di-t-butyl-2,2'-bipyridyl (0.0222 g), under oxygen
15 free conditions. The reaction mixture was heated to 130 C.
After two hours, the reaction mixture became gelatinous. The
reaction was stirred for three more hours until the mixture
was so viscous that the magnetic stir bar did not turn. The
mixture was dissolved in DMF and precipitated into water. A
20 gel-like mass was obtained and filtered. The resulting solid
was a gel having a mass of 20.0 g. The gel was dried over P205
at 70 C under vacuum for 2.5 days. Yield 4.0 g.
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(D): Macromonomers of Styrene
(i) : Synthesis of Polystvrene with a Vinyl Acetate End Group
(VAc-StVrene)
5K Polystyrene:
Cu(I)Cl (0.5188 g) and 2,2'-bipyridyl (2.40 g) were added
to a 100 ml round bottom flask and sealed with rubber septum.
The contents of the flask were placed under vacuum, then
backfilled with argon. This was repeated two additional
times. Diphenyl ether (30.0 ml), deinhibited styrene (30.0
ml) and vinyl chloroacetate (0.53 ml), all of which were
previously degassed by bubbling argon through the liquids,
were added to the flask via syringe. The reaction mixture was
then heated to 130 C for 6 hours. The reaction mixture was
then transferred into methanol to precipitate the formed
polymer. The precipitate was then twice reprecipitated from
THF into methanol. The isolated white powder was then dried
under vacuum at room temperature. Yield: 21.68 g(77.40).
GPC: Mõ = 4400, PD = 1.22.
10K Polystyrene:
Cu(I)C1 (0.5188 g) and 2,2'-bipyridyl (2.40 g) were added
to a 250 ml round bottom flask and sealed with a rubber
septum. The contents of the flask were placed under vacuum,
then backfilled with argon. This was repeated two additional
times. Diphenyl ether (60.0 ml), deinhibited styrene (60.0
ml) and vinyl chloroacetate (0.53 ml), all of which were
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previously degassed by bubbling argon through the liquids,
were added to the flask via syringe. The reaction mixture was
then heated to 130 C for 24 hours. The reaction mixture was
then transferred into methanol to precipitate the formed
polymer. The precipitate was then twice reprecipitated from
THF into methanol. The isolated white powder was then dried
under vacuum at room temperature. Yield: 44.36 g(81.3$).
GPC: Mr, = 10,500, PD = 1.25.
ii : Synthesis of Water Swellable Polymers
Copolymerization of N-Vinyl Pyrrolidinone (75 wt.o) with VAc-
Styrene (Mn = 4400; 25 wt.o) :
AIBN (0.0106 g) and VAc-styrene (2.50 g) were added to a
50 ml round bottom flask and sealed with a rubber septum. The
contents of the flask were placed under vacuum and backfilled
with argon three times. Previously degassed DMSO (20.0 ml)
and N-vinyl pyrrolidinone (7.5 ml) were added to the flask by
syringe. The reaction was then heated to 60 C for 20 hours.
A highly viscous fluid was obtained and diluted with DMF (30.0
m1). The reaction mixture was precipitated into water. The
precipitate was a swollen solid. This was filtered and dried
under vacuum at 70 C to produce the obtained polymer. The
obtained polymer was placed in a water bath for 3 days. The
equilibrium water content was 89%.
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Copolymerization of N-Vinyl Pyrrolidinone (75 wt.o) with VAc-
Styrene (Mn = 10500, 25 wt.%)
AIBN (0.0106 g) and VAc-Styrene (2.50 g) were added to a
50 ml round bottom flask and sealed with a rubber septum. The
contents of the flask were placed under vacuum and backfilled
with argon three times. Previously degassed DMSO (20.0 ml)
and N-vinyl pyrrolidinone (7.5 ml) were added L-o the flask by
syringe. The reaction was then heated to 60 C for 20 hours.
A highly viscous fluid was obtained and diluted with DMF (30.0
ml). The :2action mixture was precipitated into water. The
precipitate was a white, jelly-like mass. The liquid was
decanted, the precipitate was air-dried overnight, and then
dried under vacuum at 70 C to produce the obtained polymer.
M71 = 116,000; PD = 2.6.
After placing in a water bath for 3 days, the equilibrium
water content was determined to be 890.
Example 26: Thiocyanate transfer polymerizations
It has been previously reported that thiocyanate (SCN) is
transferred from Cu(SCN)Z to an alkyl radical at roughly the
same rate as chloride from CuCl, (Kochi et al, J. Am. Chem.
Soc., 94, 856, 1972).
A 3:1:1 molar ratio of ligand (2,2'-bipyridyl [bipy] or
4,4'-di-n-heptyl-2,2'-bipyridyl [dHbipy]) to initiator
(PhCH,SCN) to transition metal compound (CuSCPJ) was used for
each polymerization. The initiator system components were
weighed and combined in air under ambient conditions. The
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reactions were run in bulk according to the procedure of
Example 4, but at 120 C.
Reactions employing bipy were very viscous after 5 h, at
which time they were cooled to room temperature. Reactions
employing dHbipy were not viscous after 5 h, and were
therefore heated for 24 h before cooling to room temperature.
Results are shown in Table 10 below.
Table 10
Ligand M/I o Conv. Mn PDI
bipy 193 39 158,300 1.61
bipy 386 43 149,100 1.75
dHbipy 193 86 28,100 2.10
dHbipy 386 89 49,500 1.89
where "M/I" is the monomer/initiator ratio, "o Conv." refers
to the percent conversion, and "PDI" refers to the
polydispersity.
The bipy reactions showed less than optimal molecular
weight control, but the dHbipy reactions showed excellent
molecular weight control. It is believed that PDI can be
improved further by increasing the amount or concentration of
Cu(II) at the beginning of polymerization.
Example 27: synthesis of comb-shaped PSt
The macro ATRP initiator, poly(p-chloromethylstyrene),
PCMS, was synthesized by polymerizing p-chloromethylstyrene
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(0.02 mol) in benzene (50%) at 60 C for 24 hours using ICH,CN
(0.0023 mol) and AIBN (0.0006 mol). Yield: 92%. t=ir = 1150,
Diõ/iL = 1.20.
Subsequently, a degassed solution containing St (0.012
mol ), purified PVBC (9. 6 x 10"5 mol ), CuC? (1. 5 x 10'4 mol) and
bipy (4.5 x 10-' mol) was heated at 130 C for 18 hrs. Comb-
shaped PSt was obtained (yield = 95a) . r, = 18500, 1%/Mn =
1.40. At lower initial concentrations of PCMS, higher
molecular weight comb-shaped polystvrenes were formed (Mõ _
40,000 and 80,000 g/mol, as compared to linear polystyrene
standards, cf. the first three entries in Table 15)
Example 28: Synthesis of PVAc-g-PSt
Vinyl acetate end-capped PSt (PSt-VAc) was synthesized by
polymerizing St (0.019 mol) in bul}; at 130 C for 18 h using
C1CH,COOCH=CH2 (0.0018 mol), CuCl (0.0018 mol) and bipy (0.0054
mol). Yield: 95%. Mn = 1500, 1=1õ/Mõ = 1.35.
Subsequently, a degassed solution containing vinyl
acetate (5.8 x 10'' mol ), purified PSt-VAc (6.67 x 10-' mol) and
AIBN (1 x 10'4 mol) in ethyl acetate was heated at 60 C for 48
h(ca. 85% conversion of macromonomer). Final grafting
copolymer composition: Mn = 54500, M,/ri,, = 1.70.
ExamAle 29: End-Functional Polymers
One of the advantages of ATRP process is that one can
synthesize well-defined end-functional polymers by using
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functional alkyl halides and transition metal species (Scheme
4).
Z- (R') - X + n M~Lx~ X
Scheme 4
Tables 11 and i2 report the characterization data of
ATRP's of St using various functional alkyl halides as
initiators under typical ATRP experimental conditions.
From Table 11, it appears that acid-containing alkyl
halides give rise to relatively uncontrolled polymers (e.g.,
limited conversions, higher molecular weights than expected,
and relatively broad molecular weight distributions). This
suggests that CuCl may react with these alkyl halides with
f ormation of side products which disturb the "living" ATRP
process.
Using 3-chloro-3-methyl-l-butyne, the monomer conversion
was almost quantitative. However, the experimental molecular
weight is ca. 3 times as high as expected, and the
polydispersity is as high as 1.95. This suggests that
initiation is slow and the triple bond might also be attacked
by the forming radicals.
In addition, using 2- (bromomethyl) naphthalene and 9-
(chloromethyl)anthracene as initiators, the polymers obtained
showed properties as good as polymers obtained by using 1-
alkyl-2-phenylethyl halide initiators. However, 1,8-
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bis (bromomethyl) naphthalene does-not seem to be as efficient
an ATRP initiator as 2-(bromomethyl) naphthalene and 9-
(chloromethyl)anthracene under the same conditions.
More importantly, several Pst macromonomers containing
polymerizable double bonds can be obtained in a controlled
manner (Table 11). The lt-i tdMR spectrum of Pst initiated with
vinyl chloroacetate in the presence of 1 molar equiv. of CuCl
and 3 molar equiv. of bipy at 130 C shows signals at 4.0 to
5.5 ppm, assigned to vinylic end-groups. A comparison of the
integration of the vinylic protons with the protons in the
backbone gives a molecular weight similar to the molecular
weight obtained from SF.C: t.e., a functionality close to 0.90.
This suggests that the double bond is unreactive towards a
minute amount of St type radicals during ATRP of St.
Table 11: ATRP Synthesis of End-Functional Polymersa
RX CuX Conv. 21,,,141,,SEC M.jMõ
= il
C1CH2-COOH CuCl 60 3000 12500 1.50
HC=CC(CH,)ZC1 CuCl 95 4800 14100 1.90
C1CH2-CONH: CuCl 70 3500 21300 1.70
CH2CI CuCl 92 4140 6730 1.35
~ \ \ \
CH28r CuBr 96 1200 1010 1.35
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CuBr 99 52 60 4300 1.25
Cf-iZ8rCHZBr
CuBr 75 1180 820 1.25
~
~
BrCH_-CH=CH2 CuBr 99 5260 6500 1.23
" CuBr 99 1000 970 1.23
C1CH2-COOCH=CHZ CuCl 95 1000 1500 1.35
" CuCl 98 3000 3150 1.30
" CuCi 99 5000 5500 1.30
CH3CHBr-CO0CH2CH=CH: CuBr 90 4730 4580 1.40
ay Polymerization conditions: molar ratio of RX/CuX/Bpy:
1/1/3; temp: C1-ATRP, 130 C; Br-ATRP, 110 C.
b) Calculated based on Mr, = M x(D[M]/[RX]o)
Example 30: Sequential Block Copolymerization
ATRP can also be successfully used to produce well-
defined di- and tri-block copolymers by means of sequential
addition technique.
As seen in Table 12, di- and tri-block copolymers of St
and I=1A obtained are very well defined, regardless of monomer
addition order. The molecular weights are close to
theoretical, and molecular weight distributions remain very
narrow, Mõ/Mõ from - 1.0 to - 1.25. SEC traces show that
almost no first polymer contaminates the final block
copolymer.
DSC measurements of several samples in Table 12 were also
carried out. There appears to be two glass transition
temperatures around 30 and 100 C, very close to the Tg's of
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PMA and PSt, respectively. NMR analysis of the purified
polymer also shows the presence of PMA and PSt segments. All
these results indicate that well-defined block copolymers have
been synthesized.
Table 12: Synthesis of Di- and Tri- Block Copolymers Through
Sequential Addition'
!=lonomer M,,, SEC Mõ/M., M,,, caic. M,,, SEC M,,, NMR M',/Mõ
Sequence (First (First (Co- (Co- (Co- (Co-
block) block) polymer) polymer) polymer) polymer)
PMA-PSt 6040 1.25 8920 8300 --- 1.20
5580 I 1.20 10900 10580 ' --- 1.12
15100 1.14 20700 21700 --- 1.2
10000 1.25 21800 29000 27500 1.2
3900 1.25 18700 21400 --- 1.13
PSt-PMA-PSt 9000 1.25 23800 26100 25500 1.40
12400 1.25 23800 24200 --- 1.15
4000 1.25 12100 19200 18500 1.13
PMA-PSt-PMA 5300 1.13 12900 12600 --- 1.25
7700 1.14 21700 21300 I --- 1.20
a) All polymerizations were carried out at 110 C.
b) Initiators used: di-block copolymer: 1-phenylethyl
bromide; tri-block copolymers: a,a'-dibromoxylene
ATRP is superior to living ionic polymerization for
producing well-controlled block copolymers. First of all, the
experimental conditions are relatively mild. Furthermore,
cross-propagation is facile, leading to block copolymerization
regardless of monomer addition order, as exemplified by the MA
and St copolymerization above. Moreover, tri-block copolymers
can be easily obtained by using a di-functional initiator. As
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expected, star-shaped block copolymers can be obtained by
using multi-functional alkyl halides.
Example 31: Star-Shaped Polymer
(i) Synthesis of 4- and 6-arm star shaped PSt using
1, 2,4, 5-tetrakis (bromomethyl) benzene and
hexakis(bromomethyl)benzenp as initiator.
Table 13 lists the results regarding synthesis of four-
arm and six-arm star-shaped PSt using 1,2,4,5-
tetrakis (bromomethyl) benzene and hexakis(bromomethyl) benzene
as initiator, respectively. The molecular weight distribution
is fairly narrow, i.e., Mr/Mr < 1.3 The Mn of these star-
shaped polymers linearly increases with monomer conversion,
indicating the presence of negligible amount of chain in
transfer reactions (data not shown).
A key question involves whether the forming polymers have
six or four arms. Thus, ATRP of deuterated styrene was
performed using hexakis(bromomethyl) benzene as an initiator in
the presence of 2 molar equiv. of CuBr and 6 molar equiv of
bipy at 110 C, the same experimental conditions employed for
synthesizing the six-arm PSt listed in Table 13. Except for
the observation of a -CH2- resonance at ca. 1.55 ppm, the 1H
NMR signals corresponding to -CHZBr, which usually resonate at
ca. 5.0 ppm, cannot be detected at all in the 1H NMR spectrum
of the PSt-d,. This provides strong evidence that a six-arm
PSt-ds was produced.
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Table 13: Synthesis of 4- and 6-Arm PSt Using C6H,(CH;-Br)4 and
C5(CH,-Br)6 as Initiators at 110 C
Time, h Yield, 0 1,1~, calc. 1-1.,, SEC
~
4.75 90 9000 12300 1.65
5b 90 27000 31100 1.29
710 85 51200 62400 1.23
16' 92 13000 11800 1.30
16~ 89 36400 28700 1.25
a: ~R-Br],/[CuBr]o/[bpy]o = 1/2/6; b: six-arm; c: four-arm
(ii) Synthesis of 4- and 6-arm star-shaped PI-SA and PMMA
using 1,2,4,5 tetrakis(bromomethyl)benzene and
hexakis(bromomethyl)benzene as initiator
As noted in Table 14, 4- and 6-arm Pt=IA and PrII1A can also
be synthesized by using the same technique for star-shaped St
polymerization. However, it may be advantageous to lower the
concentration of the catalyst (e.g., CuBr - bipy), otherwise
gelation may occur at a relatively low monomer conversion.
This appears to confirm the radical process of ATRP. On
the other hand, it also suggests that the compact structure of
growing polymer chains may affect the "living" course of ATRP,
since at the same concentration of initiating system, MA and
MMA ATRP represents a rather controlled process, when a mono-
functional initiator was used.
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Table 14: Synthesis of 4- and 6-Arm PMA and PMMA Using
C6H2(CH,-Br) 4 and CS (CH,-Hr); as Initiator at 110 C
R-Br/CuBr/bpy polymer Time, h Yield, % M,,, calc M,,, SEC Mõ/Mõ
1/2/6 C6(PMA) 5 95 9500 10500 1.55
4 90 9000 9700 1.65
C4 ( PMMA ) 6 4.5 92 9100 12000 1.75
C6H,(PMA)4 25 gel 20000 -- --
C6H=(PMA)4 25 gel 40000 -- --
1/1/3 = 18 95 9500 6750 1.23
C6H,(PMMA). 20 0.90 9000 9240 1.72
20 0.91 18200 17500 1.49
a: Polymerization at 110 C.
Example 32: Graft Technique
Well-defined comb-shaped PSt has been successfully
obtained using PCMS as an ATRP initiator. Table 15 shows the
SEC results of final polymers. The MWD is rather narrow.
Table 15: Synthesis of Graft Copolymers Using PCMS (DPr, = 11)
as Initiator'
Monomer Time, hr Yield, Mrõ SEC Mõ/M71
St 18 95 18500 1.40
iob i- 90 38500 1.35
nn u 85 80500 1.54
BA 15 95 18400 1.60
MMA 15 95 37700 1.74
BA' 22 90 24000 1.46
MMA 22 90 46500 1.47
nc 22 85 51100 1.44
a: Polymerization at 130 C in bulk.
b: Taken from Example 27.
c: Polymerizaticn in 50% ethyl acetate solution.
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Similar to 4- and 6-arm polymers, a key question is
whether all chlorine atoms in PCMS participate in the ATRP. A
comparison of the 'H NMR spectra of PCMS and PSt-de-g-PCMS
shows that the resonances at ca. 5 ppm, corresponding to CH2C1
in PC14S, completely disappear, suggesting the formation of
pure PSt comb-copolymer.
Examole 33: Synthesis of ABA Block Copolymers with B = 2-
Ethvlhexyl Acrylate
(a) Svnthesis o-f Center B Block (a,w-Dibromopolv(2-ethylhexyl
acrylate))
To a 50 ml round bottom flask, CuBr (0.032 g), dTBiby
(0.129 g) and a,cr'-dibromo-p-xylene (0.058 g) were added. The
flask was then sealed with a rubber septum. The flask was
degassed by applying a vacuum and backfilling with argon.
Degassed and deinhibited racemic 2-ethylhexyl acrylate (10.0
ml) was then added via syringe. Degassed diphenyl ether (10.0
ml) was also added by syringe. The reaction was heated to 100
C and stirred for 24 hours. Conversion by 'H 24MR was > 90%.
Mõ = 40,500; ML/M, = 1.35.
(b) A = Methyl Methacrylate
T. the reaction mixture obtained in Example 33(a)
containing the poly(2-ethylhexyl acrylate), methyl
methacrylate (4.53 ml) was added by syringe. the reaction was
stirred at 100 C for 8 hours. Conversion of MMA > 90%. Mn
(overall) = 58,000; Mõ/I4n = 1.45.
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(c) A = Acrylonitrile -
The experiment of Example 33(a) was repeated. To the
reaction mixture containing the (2-ethylhexyl acrylate) (MT, _
40,500; t4õ/Mõ = 1.35), acrylonitrile (5.44 ml) was added by
syringe. The reaction was stirred at 100 C for 72 hours.
Conversion of acrylonitrile = 35%. M, (overall) = 47,200;
Mõ/Mõ = 1.45.
Example 34: Synthesis of MMA-BA-MMA Block Copolymer
Synthesis of a w-dibromopoly(butyl acrylate):
To a 50 ml round bottom flask, a,a'-dibromo-p-xylene
(0.0692 g), CuBr (C.0376 g), and 2,2'-bipyridyl (0.1229 g)
were added and sealed with a rubber septum. The flask was
then evacuated and filled with argon three times. Previously
degassed butyl acrylate (15.0 ml) and benzene (15.0 ml) were
added via syringe. The reaction was heated to 100 C for 48
hours, after which time the conversion was 86.5%, as
determined by 1H NMR. The reaction mixture was poured into
cold methanol (-78 C) to precipitate the polymer. The
precipitate was filtered. The obtained solid was a tacky,
highly viscous oil. Mõ = 49,000, 1. 39 .
Synthesis of boly(MMA-BA-MMAl.:
In a round.bottom flask, a,w-dibromopoly(butyl acrylate)
(2.0 g), CuBr (0.0059 g), 2,21-bipyridyl (0.0192 g) and
dimethoxybenzene (2.0 g) were added. THe flask was sealed
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with a rubber septum and placed under an argon atmosphere as
described above for the svnthesis of a,w-dibromopoly(butyl
acrylate). Degassed methyl methacrylate (0.73 ml) was added
via syringe. The reaction was heated to 100 C for 5.25
hours. The conversion was determined to be 88.8% by 'H NMR.
The reaction mixture was poured into methanol to precipitate
the polymer. The solid which was obtained was colorless and
rubbery. Mn = 75,400, t".,jMn = 1.34.
Examole 35: Synthesis of poly(p-t-butylstyrene)
To a 100 ml round bottom flask, dimethoxybenzene (25.0
g), CuCl (0.2417 g) and 2,21-bipyridyl (1.170 g) were added
and sealed with a rubber septum. The flask was then evacuated
and filled with argon three times. Degassed t-butylstyrene
(28.6 ml) and 1-phenvlethyl chloride (0.33 ml) were added via
syringe. The reaction was then heated to 130 C for 8.5
hours. The reaction mixture was precipitated into methanol,
filtered and dried. 11, = 5531. t=%JMn = 1.22.
obviously, numerous modifications and variations of the
present invention are possible in light of the above
teachings. It is therefore to be understood that within the
scope of the appended claims, the invention may be practiced
otherwise than as specifically described herein.
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