Note: Descriptions are shown in the official language in which they were submitted.
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NOVEL CHROMOPHORES FOR POLYMERIC THIN FILMS AND
OPTICAL WAVEGUIDES AND DEVICES COMPRISING THE SAME
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority to, and the benefit of, US Patent Application
09/595,221 filed June 16, 2000 entitled "Novel Chromophores For Polymeric Thin
Films
And Optical Waveguides And Devices Comprising The Same," and US Patent
Application 09/675,966 filed September 29, 2000 entitled "Novel Chromophores
For
Polymeric Thin Films And Optical Waveguides And Devices Comprising The Same."
1o FIELD OF THE INVENTION
The present invention relates to chromophores which can be used in the
preparation of polymeric thin films far waveguide media, and to optical
waveguides and
devices comprising the chromophores.
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BACKGROUND OF THE INVENTION
Thin films of organic or polymeric materials with large second order
nonlinearities in combination with silicon-based electronic circuitry can be
used in systems
for laser modulation and deflection, information control in optical circuitry,
as well as in
numerous other waveguide applications. In addition, novel processes through
third order
nonlinearity such as degenerate four-wave mixing, whereby real-time processing
of optical
fields occurs, have utility in such diverse fields as optical communications
and integrated
circuit fabrication. The utility of organic materials with large second order
and third order
l0 nonlinearities for very high frequency application contrasts with the
bandwidth limitations
of conventional inorganic electrooptic materials currently in use.
Numerous optically responsive monomers and polymers have been developed for
use in organic materials which, in turn, can be used in the waveguide
applications
described above. For example, U.S. Patent No. 5,044,725, which is incorporated
herein by
reference in its entirety, describes numerous polymer compositions which
provide suitable
nonlinear optical response. U.S. Patent No. 5,044,725 describes, for example,
a preferred
polymer composition comprising an organic chromophore containing an electron
donating
group and an electron withdrawing group at opposing termini of a bridge.
Synthesis of high performance organic, high ~,(3 electro-optic chromophores
must
2o be accomplished in order to make polymer-based electro-optic waveguides and
devices.
The synthesis of electro-optic chromophore bridge compounds and donor-bridge
compounds for organic nonlinear optical applications are generally known in
the art.
Although.: some chromophores have been reported in the literature, many of
them have
shown several and sometimes severe problems ranging from thermal instability,
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insolubility in the polymer, photodegradability, exhibition of a broad
absorption band into
the wavelength region of interest, and large birefringence upon poling.
Most recently, U.S. Patent No. 6,067,186 (the '186 patent), disclosed a class
of
organic chromophores which can result in hardened electro-optic polymers
suitable for
electro-optic modulators and other devices such as optical switch.
There continues to be a need for suitable electro-optic chromophores with
improved properties.
SUMMARY OF THE INVENTION
The present invention is -directed, in part, to compounds which can serve as
chromophores in, for example, thin films for optical waveguides and optical
devices.
These are compounds represented by Formula I
(s)
wherein:
D is an electron donating group;
B comprises at least one bivalent ring; and
R2 and R3 each, independently, are selected from the group consisting of
substituted or unsubstituted C2-C~o alkenyl, substituted or unsubstituted CZ-
Clo alkynyl,
substituted or unsubstituted aryl, substituted or unsubstituted alkylaryl,
substituted or
unsubstituted carbocycle, substituted or unsubstituted heterocycle,
substituted or
2o unsubstituted cyclohexyl, and (CH2)n O-(CH2)" where n is 1-10.
Alternatively, R2 and R3
can be selected from substituted or unsubstituted Cl-Clo alkyl, provided that
when R~ and
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R3 are both selected from substituted or unsubstituted C1-Clo alkyl the
following condition
is also met: R2 ~ R3. More preferably, chromophores of the invention have
Formula I'
(I' )
where:
RZ and R3 are further characterized in that they define a ring in which *
denotes a
spiro junction, or where * denotes a chiral center; or R2 and R3 each,
independently, are
either, substituted or unsubstituted CI-Clo alkyl, substituted or
unsubstituted CZ-CIo
alkenyl, substituted or unsubstituted Ca-Clo alkynyl, substituted or
unsubstituted aryl,
substituted or unsubstituted alkylaryl, substituted or unsubstituted
carbocyclic, substituted
or unsubstituted heterocyclic, substituted or unsubstituted cyclohexyl, or
(CH2)n O-(CH2)",
where n is 1-10. D and B have the definitions given above.
In still another aspect of the invention, the chromophores comprise novel
cyclic
bridges comprising at least one bivalent aromatic ring. Preferred compounds of
the
invention have Formula II:
D ~ K
A
R1
II
wherein D is an electron donating group; A is an electron withdrawing group; K
is O or S;
Rl is -Q-CnH2n+n -Q-(CH2)aCnF2n+u -Q-CHZOCH2C"F2n+u -Q-CH2SCHZCC"F2n+u -Q-
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CH20CH2CF3, or -Q-CH~SCHZCF3, where n is 1-10, a is 0-10, and Q is absent, O
or S;
andqis 1,2,or3.
Other preferred compounds of the invention have Formula III:
D
J
A
R1
III
5 wherein D is an electron donating group; A is an electron withdrawing group;
J is CHa, O
or S; Rl 1s -Q-CnHan+~, -Q-(CHz)aCnF2n+n -Q-CHaOCH2CnF2n+1; -Q-CH2SCH2CC"F2n+u
-Q-CH20CHZCF3, or -Q-CHzSCH2CF3, where n is 1-10, a is 0-10, and Q is absent,
O or S.
In other embodiments of the invention, the chromophores comprise novel cyclic
bridges comprising at least one bivalent or conjugated ring structure, such as
an aromatic
l0 ring, and novel electron withdrawing groups. Such compounds are generally
represented
by the structure of Formula IV:
2
wherein D is an electron donating group; K is O or S; R1 is -Q-C"H2"+n -Q-
(CHz)aCnFan+u
-Q-CH20CHaCnF2n+~, -Q-CH2SCH2CC"Fzn+1~ -Q-CH~OCHaCF3, or -Q-CH2SCH2CF3,
where n is 1-10, a is 0-10, and Q is absent, O or S; q is 1, 2, or 3; and Ra
and R3 each,
independently, are either substituted or unsubstituted C1-Clo alkyl,
substituted or
unsubstituted C2-Cio alkenyl, substituted or unsubstituted C2-Clo alkynyl,
substituted or
unsubstituted aryl, substituted or unsubstituted alkylaryl, substituted or
unsubstituted
Rl
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carbocycle, substituted or unsubstituted heterocycle, substituted or
unsubstituted
cyclohexyl, or (CH2)p O-(CHZ)n where n is 1-10. Alternatively, RZ and R3
together form a
ring structure or a substituted ring structure. Preferred compounds of this
embodiment are
represented by the structure of Formula IV'
n
(IV')
where:
R2 and R3 are further characterized in that they define a ring in which *
denotes a
spiro junction, or where '~ denotes a chiral center.
to Other useful compounds of the invention have Formula V:
V
wherein D is an electron donating group; J is CH2, O or S; Rl is -Q-C"H2n+1a -
Q-
(CH2)aCnF2n+1, -Q-CH2OCH2CnF2n+1, -Q-CHaSCHaCCnFan+1, -Q-CHzOCH2CF3, or -Q-
CHaSCH2CF3, where n is 1-10, a is 0-10, and Q is absent, O or S; and RZ and R3
each,
15 independently, are either H, substituted or unsubstituted C1-ClO alkyl,
substituted or
unsubstituted C2-Clo alkenyl, substituted or unsubstituted C2-CIO alkynyl,
substituted or
v
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unsubstituted aryl, substituted or unsubstituted alkylaryl, substituted or
unsubstituted
carbocycle, substituted or unsubstituted heterocycle, substituted or
unsubstituted
cyclohexyl, or (CH2)ri O-(CHZ)" where n is 1-10. Alternatively, RZ and R3
together form a
ring structure or a substituted ring structure. Preferred chromophores of this
embodiment
include compounds of Formula (V' )
CN
(V')
i0 where:
R2 and R3 are further characterized in that they define a ring in which *
denotes a
spiro junction, or where * denotes a chiral center.
The present invention is also directed to optical waveguides comprising a thin
film medium having Formula VI:
L
P C~ n~ P P' C P P'
L
S or \ S S S
or \M/
Mn M n ,
VI
wherein P and P' are polymer main chain units, which can be the same mer unit
or
different mer unit, and C is a comonomer unit where n is an integer greater
than zero and
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n' is 0 or an integer greater than zero; S is a pendant spacer group having a
linear chain
length of between about 2-12 atoms. M is a compound having either Formula I,
Formula
I', Formula II, Formula III, Formula IV, Formula IV', Formula V, or Formula
V', as
described above.
The phrase "electron donating group" is used synonymously with "electron
donator" and refers to substituents which contribute electron density to the ~-
electron
system when the conjugated electron structure is polarized by the input of
electromagnetic
energy.
The phrase "electron withdrawing group" is used synonymously with "electron
accepting group" and "electron acceptor" and refers to electronegative organic
compounds
or substituents which attract electron density from the ~-electron system when
the
conjugated electron structure is polarized by the input of electromagnetic
energy.
The term "chromophore" as used herein refers to an optical compound
comprising an electron donating group and an electron withdrawing group at
opposing
termini of a conjugated ~-electron system.
The phrase "cyclic bridge" is used to refer to bivalent cyclic structures
which
serve to couple the electron donating and withdrawing groups.
The present invention is also directed to optical devices comprising the
optical
waveguides described above.
DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
The present invention is directed, in part, to novel electro-optic
chromophores
which have utility in organic nonlinear optical applications such as polymeric
thin films
for optical waveguides and optical devices. Such polymeric thin films are
described in, for
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example, U.S. Patent Numbers 5,044,725, 4,795,664, 5,247,042, 5,196,509,
4,810,338,
4,936,645, 4,767,169, 5,326,661, 5,187,234, 5,170,461, 5,133,037, 5,106,211,
and
5,006,285, each of which is incorporated herein by reference in its entirety.
The inventive chromophores have several advantageous features which are not
found in other known or commercially available chromophores. For example, we
have
found that the introduction of a chiral center, preferably in the acceptor
portion of the
molecule, and more preferably as a racemic mixture, greatly increases the
chromophore's
solubility. We have found that solubility is enhanced the greater the
structural or
functional differences between RZ and R3. For example, we have observed
significantly
enhanced solubility when one of RZ or R3 is a chain and the other is a ring
structure; or
when one is a short chain (up to three carbons), and the other is a long chain
(say, C4-
C18). This increased solublility in turn can lead to an enhanced nonlinearity
of the final
material in many cases. It is known that the introduction of long chain alkane
groups
increase the solubility of chromophores, and that as the number and size of
the alkane
moieties increase, both the solubility and bulk material nonlinearity are
greatly improved.
The chromophores of the present invention have an enhanced solubility over the
dimethyl
types of the prior art.
While there may be other factors contributing to this improved property, we
have
found that one major difference between the inventive acceptors and those of
the prior art
2o is the presence of chiral centers in the inventive acceptors. It is known
that the physical
characteristics like melting point and solubility are different for the pure
enantiomer than
for the racemic mixture. Several examples of this difference exist. For
example, pure
chiral (D) lycine has a melting point of 218 C and is very soluble at room
temperature.
The racimate has a melting point of 170 C and is considered infinitely soluble
in room
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temperature water. Also, pure enantiomers of Mandelic acid have a melting
point of 133
C while the racimate has a melting pint of 120 C. (R )-(+)-Mandelonirile has a
melting
point of 29 C while the racimate is an oil at room temperature.
In the specific chemistry of the present invention, the chiral centers do not
form a
5 single chiral compound but rather a mixture of racemic enantiomers, which
when
introduced into chromophores increase the solubility of the chromophores due
to a
depression of the melting point. In fact, we. have found that the inventive
compounds tend
to form glassy solids rather than crystalline materials. Without intending to
be bound by
theory, we believe that the present chemistry results in improvements in the
nonlinearity of
10 the bulk polymer because of the incorporation of a racemic chiral center in
the
chromophores.
The electro-optic chromophores of the invention exhibit thermal stability to
temperatures from 260 C to 310 C. These chromophores also show great
solubility in
most common organic solvents and, thus, are useful when used as a guest
additive in most
polymer films for waveguides. In addition, under intense UV-irradiation (365
nm, dosage
3 J/cm2 up to 13 minutes), the chromophores of the invention show no changes
of the UV-
VIS-NIR spectrum, which indicates that the chromophores axe photostable. The
chromophores also demonstrate an adjustable absorption band away from normal
communications wavelengths, which can be very important for reducing optical
loss at
communication wavelengths. The chromophores of the invention have significant
three-
dimensional design which can prevent chromophore-chromophore anti-parallel
stacking.
Because of the flexible side chain substitutions, the chromophores of the
invention show
significantly reduced birefringence losses. In some of the chromophores of the
invention,
there is unique regiospecific substitution on the bridging thiophene ring,
which allows the
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electron acceptor to more easily access the conjugated ~-system of the bridge
and allows
the molecule backbone to be flatter. In addition, some of the preferred
chromophores of
the invention have hydroxyl groups on the electron donor termini in order to
easily process
the chromophore into hydroxyl compatible organic and inorganic polymer
reactions to
make soluble chromophores, polymers and copolymers, as well as can be used to
make
highly soluble "guest" chromophores for guest-host applications.
The present invention is directed, in part, to compounds which can be employed
as chromophores in polymeric thin films for optical waveguides. In preferred
embodiments of the invention, such compounds comprise novel electron
withdrawing
l0 groups having Formula I:
R3
p CN
R2
'CN
CN
D B
I
where: D is an electron donating group. Preferred electron donating groups are
described
in, for example, U.S. Patent Numbers 5,044,725, 4,795,664, 5,247,042,
5,196,509,
4,810,338, 4,936,645, 4,767,169, 5,326,661, 5,187,234, 5,170,461, 5,133,037,
5,106,211,
and 5,006,285, each of which is incorporated herein by reference in its
entirety.
Preferably, D is selected from the group consisting of, but not limited to,
phenyl rings)
substituted in the para position by, for example, amino, alkylamino,
dialkylamino,
dialkylanilino, 1-piperidino, 1-piperazino, 1-pyrrolidino, acylamino,
hydroxyl, thiolo,
alkylthio, arylthio, alkoxy, aryloxy, acyloxy, alkyl, vinyl, 1,2,3,4-
tetrahydroquinolinyl, and
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the like. The most preferred electron donating groups are substituted and
unsubstituted
phenyl-N(CH2CHaOH)2.
B is a cyclic bridge which couples the electron withdrawing group and the
electron donating group. Preferably, B is at least one bivalent ring.
Preferred cyclic
bridges comprise one or a plurality of bivalent rings. Preferred bivalent
rings which can
be employed as cyclic bridges in the present application are described in, for
example,
IJ.S. Patent Numbers 5,044,725, 4,795,664, 5,247,042, 5,196,509, 4,810,338,
4,936,645,
4,767,169; 5,326,661, 5,187,234, 5,170,461, 5,133,037, 5,106,211, and
5,006,285, each of
which is incorporated herein by reference in its entirety. Ring B can be
aromatic or non-
aromatic. Preferably, B is selected from the group consisting of, but not
limited to,
R4 R4 R4
i i
CH CH ~ ~ ,
J 1-5 ~ ~ 1-3
R~ a. R4
CH CH
s~-5 s s
1-3
R4 R4
and
CH CH i-3
S 4 L s S R4
R
CH CH CH C
L s ~ i-3
where R4 is H, OH, C1-C1o alkyl, alkenyl, or alkynyl, halogen, and the like.
R4 can also be
-Q-CnHZn+~, -Q-(CH2)aCnF'2n+~ ~ -Q-CH20CHZCnFZn+~ ~ -Q-CHZSCH2CCnF2n+1 ~ -Q-
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CH20CHZCF3, or -Q-CH2SCH2CF3, where n is 1-10, a is 0-10, and Q is absent, O
or S;
and q is 1, 2, or 3.
R2 and R3 each, independently, are selected from the group consisting of, but
not
limited to, substituted or unsubstituted CI-Clo alkyl, substituted or
unsubstituted CZ-Clo
alkenyl, substituted or unsubstituted C2-Clo alkynyl, substituted or
unsubstituted aryl,
substituted or unsubstituted alkylaryl, substituted or unsubstituted
carbocycle, substituted
or unsubstituted heterocycle, substituted or unsubstituted cyclohexyl, (CHZ)"O-
(CH2)n
where n is 1-10, and the like. "Cl-Cio" refers to Cl, CZ, C3, C4, C5, C6, C~,
Cg, C9, Coo, and
all combinations of ranges thereof. Preferably, when R2 and R3 are both
selected from
to substituted or unsubstituted Cl-Clo alkyl the following condition is also
met: R2 ~ R3.
More preferably, R2 and R3 define a ring in which * denotes a spiro junction,
or where
denotes a chiral center.
The substituted alkyl, alkenyl, alkynyl, carbocyclic, and heterocyclic groups
can
comprise one or a plurality of substituents including, for example, fluorine,
chlorine, D,
and the like. In addition, the heterocyclic groups can comprise O, N, S, and
the like.
The aryl groups preferably include, but are not limited to, benzyl, phenyl,
fluorenyl, and naphthyl. The aryl groups, carbocycles, heterocycles, and
cyclohexyl can
also be substituted by one or a plurality of substituents including, for
example, D, halides,
including fluorine, chlorine and bromine. The alkylaryl groups preferably
comprise Cl-Clo
2o alkyl and the substituted alkylaryl groups comprise the substitutions for
the alkyl and aryl
groups described above.
In more preferred embodiments of the invention, R2 and R3 each, independently,
are selected from the group consisting of benzyl, carbocycle, heterocycle,
cyclohexyl,
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phenyl, cycloalkyl, cycloalkenyl, and substituted phenyl. Additional moieties
for R2
and/or R3, independently, include, but are not limited to the following:
and the like.
In even more preferred embodiments of the invention, one of R2 and R3 is CH3
and the other of RZ and R3 is a substituted phenyl. Preferably, the
substituted phenyl is
selected from the group consisting of, but not limited to:
Cl
0 0 0
0
'C1 ~Cl
Bu F Cl C1
and the like.
Alternatively, R2 and R3 together form a ring ~ structure or a substituted
ring
structure from 3 to 7 atoms total with 5 or 6 atoms being preferred.
Preferably, the ring
structure is substituted or unsubstituted carbocycle, substituted or
unsubstituted
heterocycle, or substituted or unsubstituted cyclohexyl or cyclopentyl. The
substituted
ring structure can comprise substituents including, but not limited to,
halides, including
fluorine, chlorine and bromine. A preferred compound having a ring structure
formed by
Ra and R3 comprises
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The electron withdrawing groups of the present invention are preferably
prepared
according to Scheme I:
t-BuLi O
THF
O
3" 2
R R
HCI/MeOH/H20
CN R3 OH O
R O
HC1 K2C03/THF/ether
R2 N ~ CH2(CN)2
Ra R6
R6 CN
Scheme I
Compounds having Formula I are preferably prepared by the following steps
depicted in Scheme I: a) providing an alkylvinylether, b) contacting the
alkylvinylether
with a strong base to form a first intermediate compound, c) contacting the
first
intermediate compound with a ketone to form a second intermediate compound,
and d)
1o reacting the second intermediate compound with dicyanomethane in the
presence of a
second base to form an electron withdrawing group portion of a compound having
Formula I. Each of the above mentioned steps is described in greater detail
below.
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In preferred embodiments of the invention, an alkylvinylether in a solvent is
the
starting material. The solvent is, preferably, tetrahydrofuran (THF), 1,4-
dioxane, or the
like. Although the alkylvinylether depicted in Scheme I is ethylvinylether,
other
alkylvinylethers can be used. The alkylvinylether preferably comprises the
formula CH3-
(CHa)X O-CH=CHR6, where x is 1-3 and R6 is Cl-C4 alkyl. Most preferably, the
alkylvinylether is methylvinylether or ethylvinylether.
The alkylvinylether is contacted with a strong base to form a first
intermediate
compound. Preferably, the strong base has a pKa greater than the ethylinic C-H
bond a to
the oxygen function of the alkylvinylether. For example, see Advanced Organic
to Chemistry, Third Ed., Jerry March, 1985, Table 1, pp. 220-222. In preferred
embodiments
of the invention, the strong base is an alkyl lithium, or an alkali metal salt
of an alkyl
anion, including, but not limited to, t-BuLi or sec-BuLi. The alkylvinylether
is preferably
contacted with the strong base between about -70 C and -85 C, most preferably
at about
-78 C.
The first intermediate compound is contacted with a ketone and an
acid/alcohol/water solution to form a second intermediate compound. Numerous
acid/alcohol/water solutions known to those skilled in the art can be used in
the present
invention. The acid/alcohol/water solution is preferably HCl/MeOH/H20,
HBr/EtOH/H20, or H2SO4/EtOH/H2O. Preferably, the contacting is at room
temperature.
2o Preferably, the pH is adjusted between I and 4.
Preferably, the ketone comprises R3-C(=O)R2, wherein RZ and R3 each,
independently, are selected from the group consisting of, substituted and
unsubstituted Cl-
Clo alkyl, substituted and unsubstituted C1-Clo alkenyl, substituted and
unsubstituted C1-
Clo alkynyl, substituted and unsubstituted aryl, substituted and unsubstituted
alkylaryl,
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substituted and unsubstituted carbocycle, substituted and unsubstituted
heterocycle,
substituted and unsubstituted cyclohexyl, and (CH2)~-O-(CHa)" where n is 1-10.
1 "Ci-Cio" refers to C1, C2, C3, C4, C5, C6, C~, C8, C9, Clo, and all
combinations of
ranges thereof.
Preferably, the C=C and C=C bonds of the alkenyl and alkynyl groups are not
immediately adjacent or conjugated to the carbonyl group of the ketone
compound.
The substituted alkyl, alkenyl, alkynyl, carbocyclic, and heterocyclic groups
can
comprise one or a plurality of substituents including, for example, fluorine,
chlorine, D,
and the like. In addition, the heterocyclic groups can comprise O, N, S, and
the like.
to The aryl groups preferably include, but are not limited to, benzyl, phenyl,
fluorenyl, and naphthyl. The aryl groups, carbocycles, heterocycles, and
cyclohexyl can
also be substituted by one or a plurality of substituents including, for
example, D, halides,
including fluorine, chlorine and bromine. The alkylaryl groups preferably
comprise C1-Cjo
alkyl and the substituted alkylaryl groups comprise the substitutions for the
alkyl and aryl
groups described above.
In more preferred embodiments of the invention, RZ and R3 each, independently;
are selected from the group consisting of benzyl, carbocycle, heterocycle,
cyclohexyl,
phenyl, cycloalkyl, cycloalkenyl, and substituted phenyl. Additional moieties
for R2
and/or R3, independently, include, but are not limited to the following:
2o and the like.
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In even more preferred embodiments of the invention, one of R2 and R3 is CH3
and the other of R2 and R3 is a substituted phenyl. Preferably, the
substituted phenyl is
selected from the group consisting of, but not limited to:
F C1
0 0 0
0
'C1 'CI
Bu F C1 C1
and the like.
Alternatively, R~ and R3 together form a ring structure or a substituted ring
structure from 3 to 7 atoms total with 5 or 6 atoms being preferred.
Preferably, the ring
structure is substituted or unsubstituted carbocycle, substituted or
unsubstituted
heterocycle, or substituted or unsubstituted cyclohexyl or cyclopentyl. The
substituted
ring structure can comprise substituents including, but not limited to,
halides, including
fluorine, chlorine and bromine. A preferred compound having a ring structure
formed by
R2 and R3 comprises
The second intermediate compound is reacted with dicyanomethane in the
presence of a second base to form the electron withdrawing group portion of a
compound
having Formula I. The second base is preferably a metal alkoxide including,
but not
limited to, NaOCZHs. After contacting the second intermediate compound with
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dicyanomethane in the presence of a second base, dilute acid such as, for
example, HC1, is
added for neutralization of the resultant electron withdrawing group.
The electron withdrawing group comprises R6 which is preferably selected from
the group consisting of unbranched substituted or unsubstituted C1-C4 alkyl,
unbranched
substituted or unsubstituted C2-C4 alkenyl, unbranched substituted or
unsubstituted Ca-C4
alkynyl. The substituted alkyl, alkenyl, and alkynyl groups can comprise one
or a plurality
of substituents including, for example, fluorine. In preferred embodiments of
the
invention, R6 is 'selected from the group consisting of unbranched CI-C4
alkyl, C1-C4
alkenyl, and C1-C4 alkynyl. In more preferred embodiments of the invention, R6
is CH3.
to The present invention is also directed, in part, to compounds which can be
employed as chromophores in polymeric thin films for optical waveguides
wherein the
compounds comprise novel bridge groups which couple the electron withdrawing
and
donating groups of the chromophore. Preferred compounds of the invention have
Formula
II:
D ~ K
A
Ri
i5 R
D is an electron donating group. Preferred electron donating groups are
described
above.
A is an electron withdrawing group. Preferred electron withdrawing groups are
described in, for example, U.S. Patent Numbers 5,044,725, 4,795,664,
5,247,042,
ao 5,196,509, 4,810,338, 4,936,645, 4,767,169, 5,326,661, 5,187,234,
5,170,461, 5,133,037,
5,106,211, and 5,006,285, each of which is incorporated herein by reference in
its entirety.
Preferably, A is selected from the group of molecular units containing, but
not limited to,
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nitro, cyano, haloalkyl, acyl, carboxy, aryloxy, carboxamido, alkoxysulfonyl,
aryloxysulfonyl, -CH=C(CN)~, -C(CN)=C(CN)2, S02CF3, alkanoyloxy,
O \ X S \ X
~d -
N / X N / X
where X is H, D, F, CN, N02, or CF3.
5 R~ is -Q-C"H2n+~, -Q-(C=Hz)aCnF2n+~~ -Q-CH20CH2C"FZn+~~ -Q-~H2SCH2CC"F~"+1,
-Q-CHZOCH2CF3, or -Q-CHZSCH~CF3, where n is 1-10, a is 0-10, and Q preferably
is
either absent or, when present, O or S; q is 1, 2, or 3. More preferably, Rl
is C4-CIO or
fluorine substituted C4-Cio.
A compound having Formula II can be prepared using a thiophene cyclic bridge
l0 which preferably comprises Formula VII:
Z X
Rn
VII
Preferably, K is O or S.
Preferably, R1 is -Q-CnH~"~.t, -Q-(CH2)aCnFan+n -Q-CHaOCH2C"F2n+u -Q-
CH2SCH2CC"F2~,+I, -Q-CHaOCHaCF3, or -Q-CH2SCH2CF3, where n is 1-10, a is 0-10,
and
15 Q preferably is either absent or, when present, O or S. Other halogens or
deuterium can be
used in place of F. In more preferred embodiments of the invention, Ri is C4-
Clo or
fluorine substituted C4-Cio.
X preferably has the formula -(CH=CH)b-C(=O)H, where b is 0-3. The terminal
aldehyde group serves as the preferred site of reaction with electron
withdrawing groups.
20 In more preferred embodiments of the invention, b is 0 so that X is -
C(=O)H.
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21
Z is a chemical group that is capable of being linked to a donor and includes,
but
is not limited to, Br, I, -CH2-Br, -CH2-OH, -CH3, -C(=O)H, and the like. Those
skilled in
the art can use additional groups known to those skilled in the art to couple
a bridge
compound to a donor. Another Z group that can be used to link a bridge
compound to a
donor is
Bu
Bu + P CH2
Y_
Bu
where Y- is a counter ion including, but not limited to, Br or C1-.
In other embodiments of the invention, preferred compounds of the invention
have Formula III:
D
J
1 A
R III
D is an electron donating group and A is an electron withdrawing group as
described above. J is CH2, O or S.
R1 is -Q-CnH2n+n -Q-(CH2)aCnF2n+n -Q-CH~,OCH~C"FZn+1~ -Q-CH2SCH~CCnFZn+u
-Q-CH20CH2CF3, or -Q-CH2SCH2CF3, where n is 1-10, a is 0-10, and Q is absent,
O or S.
More preferably, Rl is C4-Clo or fluorine substituted C4-Clo.
A compound having Formula IV can be prepared using a dihydronaphthyl cyclic
bridge which preferably comprises Formula VIII:
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22
Z J
R1 X
VIII
Preferably, J is CH2, O or S.
Preferably, Rl is H, -Q-C"Ha"+1 ~ -Q-(CHz)aCnF2n+i a -Q-CH20CH~CnF2a+i ~ -Q-
CHZSCH2CC"F2~+1, -Q-CH20CH~,CF3, or -Q-CH2SCHZCF3, where n is 1-10, a is 0-10,
and
Q is absent, O or S. Other halogens can be used in place of F. In more
preferred
embodiments of the invention, Rl is C4-Clo or fluorine substituted C4-Clo.
X preferably has the formula (C=O)H or C=CH(-CH=CH)d-C(=O)H, where d is
0-3. The terminal aldehyde or ketone group serves as the preferred site of
reaction with
electron withdrawing groups. In more preferred embodiments of the invention, X
is
(C=O)H.
Z is a chemical group that is capable of being linked to a donor, as described
above.
The present invention is also directed to compounds which can be employed as
chromophores in polymeric thin films for optical waveguides wherein the
compounds
comprise novel bridge groups and novel electron withdrawing groups; and are
represented
by Formula IV:
z
D
where, K is O or S; and
Rl iv
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23
R1 is -Q-C"H2n+~, -Q-(CH2)aCnF2n+~~ -Q-CH20CH2C"F2n+1, -Q-CH2SCH2CC"Fzn+~,
-Q-CH20CH2CF3, or -Q-CH2SCHZCF3, where n is 1-10, a is 0-10, and Q is absent,
O or S,
and q is 1, 2, or 3. In more preferred embodiments of the invention, RI is C4-
CIO or
fluorine substituted C4-CIO. More preferred compounds of this embodiment of
the
invention are represented by Formula IV':
(IV' )
1o where:
R2 and R3 are further characterized in that they define a ring in which *
denotes a
spiro junction, or where * denotes a chiral center.
Alternatively, RZ and R3 each, independently, are selected from the group
consisting of, but not limited to, substituted or unsubstituted CI-Clo alkyl,
substituted or
unsubstituted Ca-CIO alkenyl, substituted or unsubstituted C2-CIO alkynyl,
substituted or
unsubstituted aryl, substituted or unsubstituted alkylaryl, substituted or
unsubstituted
carbocycle, substituted or unsubstituted heterocycle, substituted or
unsubstituted
cyclohexyl, (CH2)n O-(CH2)n where n is 1-10, and the like. More preferably, R2
and R3
each, independently, are selected from the group consisting of substituted or
unsubstituted
2o aryl, substituted or unsubstituted alkylaryl, and substituted or
unsubstituted cyclohexyl.
More preferably, RZ and R3 each, independently, are selected from the group
consisting of
benzyl, cyclohexyl, and substituted or unsubstituted phenyl. More preferably,
one of RZ
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24
and R3 is CH3 and the other of R2 and R3 is a substituted phenyl. Most
preferably, one of
R2 and R3 is
O
,a
and the other of R2 and R3 is CH3.
Alternatively, RZ and R3 together form a ring structure or a substituted ring
structure from 3 to 7 atoms total with 5 or 6 atoms being preferred.
Preferably, the ring
structure is substituted or unsubstituted carbocycle, substituted or
unsubstituted
heterocycle, or substituted or unsubstituted cyclohexyl or cyclopentyl. The
substituted
ring structure can comprise substituents including, but not limited to,
deuterium and
halides, including fluorine, chlorine and bromine. A preferred compound having
a ring
structure formed by R~ and R3 comprises
D is an electron donating group as described above.
In other embodiments of the invention, useful compounds are represented by the
structure of Formula V:
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CN
V R3 CN
where, J is CHa, O or S.
Preferably, Rl is -Q-C"H2n+n -Q-(CHa)aCnF2"+n -Q-CHZOCH~CnF2n+n -Q-
CH2SCH2CC"F2"+1, -Q-CHzOCH2CF3, or -Q-CH2SCH2CF3, where n is 1-10, a is 0-10,
and
5 Q is absent, O or S. In more preferred embodiments of the invention, Rl is
C~.-Clo or
fluorine substituted C4-Coo. More preferred compounds of this embodiment are
represented by the structure of Formula V':
(V')
where, R~ and R3 are further characterized in that they define a ring in which
* denotes a
spiro junction, or where * denotes a chiral center.
Alternatively, RZ and R3 each, independently, are selected from the group
consisting of, but not limited to, substituted or unsubstituted Cl-Cio alkyl,
substituted or
unsubstituted C2-Cio alkenyl, substituted or unsubstituted C2-Cio alkynyl,
substituted or
unsubstituted aryl, substituted or unsubstituted alkylaryl, substituted or
unsubstituted
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26
carbocycle, substituted or unsubstituted heterocycle, substituted or
unsubstituted
cyclohexyl, (CHZ)n O-(CH2)" where n is 1-10, and the like. More preferably, RZ
and R3
each, independently, are selected from the group consisting of substituted or
unsubstituted
aryl, substituted or unsubstituted alkylaryl, and substituted or unsubstituted
cyclohexyl.
More preferably, RZ and R3 each, independently, are selected from the group
consisting of
benzyl, cyclohexyl, and substituted or unsubstituted phenyl. More preferably,
one of R2
and R3 is CH3 and the other of Rz and R3 is a substituted phenyl. Most
preferably, one of
Ra and R3 is
0
~Cl
CI
and the other of R2 and R3 is CH3.
l0 Alternatively, RZ and R3 together form a ring structure or a substituted
ring
structure from 3 to 7 atoms total with 5 or 6 atoms being preferred.
Preferably, the ring
structure is substituted or unsubstituted carbocycle, substituted or
unsubstituted
heterocycle, or substituted or unsubstituted cyclohexyl. The substituted ring
structure can
comprise substituents including, but not limited to, deuterium and halides,
including
fluorine, chlorine and bromine. A preferred compound having a ring structure
formed by
R2 and R3 comprises
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27
D is an electron donating group as described above.
The present invention is also directed, in part, to optical waveguides
comprising
polymeric this films having comprising the chromophores of the invention. In
preferred
embodiments of the invention, optical waveguides comprising a thin film medium
have
Formula VI:
L
P C~ n~ p . P' C P P'
S or ~ S ~ L n ~S S/
~M'~
M n M n
VI
P and P' are polymer main chain units, which can be the same mer unit or
different mer unit, and C is a comonomer unit where n is an integer greater
than zero and
n' is 0 or an integer greater than zero. Polymers and copolymers that may be
employed in
the present invention are described in, for example, U.S. Patent Numbers
5,044,725,
4,795,664, 5,247,042, 5,196,509, 4,810,338, 4,936,645, 4,767,169, 5,326,661,
5,187,234,
5,170,461, 5,133,037, 5,106,21 l, and 5,006,285, each of which is incorporated
herein by
reference in its entirety. The polymers of the invention can be a homopolymer
or a
copolymer. Preferred polymers arid copolymers include, but axe not limited to,
acrylate,
vinyl carboxylate, substituted arylvinyl, vinyl halide, vinyl carboxylate,
alkene, alkadiene,
arylvinyl, methacrylate, vinyl chloride, vinyl acetate, vinyl ether, ethylene,
propylene,
isobutylene, 1-butene, isoprene, styrene, and the like.
Preferably, the polymers of the invention comprise an external field-induced
orientation and alignment of pendant side chains. Preferably, the polymer main
chain can
2o be a structural type such as polyvinyl, polyoxyalkylene, polysiloxane,
polycondensation,
and the like. A polymer can be applied to a supporting substrate by
conventional means,
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28
such as spin coating, dip coating, spraying, Langmuir-Blodgett deposition, and
the like.
Thin film optical waveguide medium of the present invention after fabrication
can be
subjected to an external field to orient and align uniaxially the polymer side
chains. In one
method the polymer medium is heated close to or above the polymer glass
transition
temperature Tg, then an external field (e.g., a DC electric field) is applied
to the medium of
mobile chromophore molecules to induce uniaxial molecular alignment of the
chromophore polymer side chains or guests in a guest-host system parallel to
the applied
field, and the medium is cooled while maintaining the external field effect.
S is a pendant spacer group having a linear chain length of between about 2-12
1o atoms. Pendant spacer groups that may be employed in the present invention
are described
in, for example, U.S. Patent Numbers 5,044,725, 4,795,664, 5,247,042,
5,196,509,
4,810,338, 4,936,645, 4,767,169, 5,326,661, 5,187,234, 5,170,461, 5,133,037,
5,106,211,
and 5,006,285, each of which is incorporated herein by reference in its
entirety.
M is a chromophore compound having Formula I, Formula I', Formula II,
Formula III, Formula IV, Formula IV', Formula V, or Formula V', described
above.
The present invention is also directed, in part, to optical devices comprising
the
optical waveguides of the invention. Optical devices are described in, for
example, U.S.
Patent Numbers 5,044,725, 4,795,664, 5,247,042, 5,196,509, 4,810,338,
4,936,645,
4,767,169, 5,326,661, 5,187,234, 5,170,461, 5,133,037, 5,106,211, and
5,006,285, each of
which is incorporated herein by reference in its entirety. Preferred optical
devices include,
but are not limited to, laser frequency converters, optical interferometric
waveguide gates,
wideband electrooptical guided wave analog-to-digital converters, optical
parametric
devices, and the like, as described in U.S. Pat. No. 4,775,215, which is
incorporated herein
by reference in its entirety.
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29
The invention is further illustrated by way of the following examples which
are
intended to elucidate the invention. These examples are not intended, nor are
they to be
construed, as limiting the scope of the disclosure.
EXAMPLES
Example 1: General Synthesis Of Dicyanomethylenedihydrofurans
To a solution of 0.33 mol of ethyl vinyl ether in 150 ml of dry THF, 0.3 mol
of t-
BuLi in pentane was added dropwise at 78 C. The mixture was stirred and
allowed to
warm up slowly to 0 C and subsequently cooled to -78 C again. Next, 0.25 mol
of
to cyclohexyl phenyl ketone dissolved in a minimum of dry THF was added
dropwise. The
mixture was stirred overnight at room temperature, then acidified using
HCl/MeOH/THF/HZO solution to pH 1-4. After stirring this mixture for two
hours, most
of the solution was evaporated using a rotary evaporator. The remaining
mixture was
extracted with ethyl ether (3 x 100 ml). The organic solution was washed with
NaHC03,
i5 brine, and DI water. This mixture was then dried over anhydrous MgS04.
After
evaporating the ether, the crude product was purified by column chromatography
(5%
ethyl acetate in hexane) to give pure alpha-hydroxy ketone (30 g).
The hydroxy ketone synthesized above (0.02 mol) was mixed with malononitrile
(0.04 mol) in ethyl alcohol at 20% w/v based on malononitrile cooled in an ice
bath. To
2o this, 20 ml of 1 M NaOC2H5/EtOH was added dropwise. The mixture was allowed
to stir
overnight. After neutralization by concentrated HCl to pH 6, the solvent was
evaporated
by vacuum. The residue was dissolved into CH2Cl2 and filtered to remove the
undissolved
solid. After evaporating the CHaCl2, the crude product was purified by
recrystalization
from ethanol to give the dicyanomethylenedihydrofuran compound ( 1.25 g).
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Alternatively, and more preferably, the hydroxy ketone synthesized above (0.02
mol) was mixed with malononitrile (0.04 mol) and potassium carbonate (0.02
mol) in THF
(40 ml) and EtOH (2 ml). To this mixture, a catalytic amount of 18-crown ether
was
added. The mixture was stirred and allowed to reflux overnight. The solid was
filtered
5 off, followed by evaporation of most of the solvent. The crude mixture was
purified by
column chromatography (CH2C12) to give the dicyanomethylenedihydrofuran
compound
{1.5 g) shown below (melting point, MP = 194-196 C).
~N
Example ~: Preparation of a Dicyanomethylenedihydrofuran-based Electron
1o Acceptor
To a solution of ethylvinylether (28.8 g in 300 ml of THF) was added 176 ml of
t-
BuLi dropwise at -78 C. The mixture was slowly warmed to 0 C and subsequently
cooled
to -78 C again. Cyclohexanone (30 g in 30 ml of THF) was added dropwise and
the
15 'mixture was slowly warmed to room temperature and stirred for an
additional four hours.
A solution of methanol (70 ml), water (20 ml) and cone. HCl ( 10 ml) was
slowly added to
the reaction mixture until a pH of about 2-3 was obtained. The mixture was
stirred
overnight and neutralized to pH 7 by addition of a 20% solution of NaHC03 in
water and
the solvent was evaporated. The residual solvent was extracted by ether (3 x
100 ml).
2o The ether solution was washed with NaHC03 (50 ml), brine (100 ml), and
dried over
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31
anhydrous MgS04. After removal of the ether, vacuum distillation of the
intermediate
yielded 36g.
CH2(CN)2 (13.2 g) and a 1 M solution of NaOC2H5 (0.1 mole) were mixed in an
ice bath. Approximately 14.2 g of the intermediate prepared as described above
and
dissolved in a minimum of EtOH was added dropwise and stirred overnight at
room
temperature. The mixture was neutralized by 8 ml of conc. HCl to a pH of 6.0
and the
solid material was filtered off and the remaining solution was evaporated. The
residue
from the solution was dissolved into CHaCla, filtered again, followed by
evaporating the
CHZCl2. The rest of the mixture was recrystalized from ethanol (150 ml) to
give 6.1 g of
l0 the final compound shown below (mMP = 239-24.1 C).
CN
CN
O RCN
Example 3: Preparation of a Dicyanomethylenedihydrofuran-based Electron
Acceptor
To a solution of ethylvinylether (21.6 g in 300 ml of THF) was added 110 ml of
t-
BuLi dropwise at -78 C. The mixture was warmed to 0 C and subsequently cooled
to -78
C again. 5', 4'-dichloroacetophenone (30.5 g) was dissolved into 150 ml of THF
and then
added dropwise. This mixture was run overnight at room temperature. A solution
of HCl
(10 ml), methanol (70 ml), and water (20 ml) was added to the reaction the
next day. The
mixture was adjusted to pH 4 and allowed to stir overnight. NaHCO3 was added
to
neutralize this solution to pH 7. The mixture was extracted by ether (3 x 100
ml). The
combined organic acid mixture was washed with NaHC03 (50 ml), brine ( 100 ml),
and
dried over anhydrous MgS04. Vacuum distillation of the intermediate yielded 55
g.
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32
CH2(CN)2 (13.2 g) and a 1 M solution of NaOCZHs (0.1 mole) were mixed in an
ice bath. Approximately 15 g of the intermediate prepared as described above
and
dissolved in EtOH was added dropwise and stirred overnight at room
temperature. The
mixture was neutralized by 8 ml of conc. HCL to a pH of 6.0 and the solid
material was
filtered and the resulting solution evaporated. The residue was dissolved into
CH2C12,
filtered again, followed by evaporating the CH2C12. The rest of the mixture
was
recrystalized from ethanol (150 ml) to give 5.5 g of the final compound shown
below (MP
= 110-111 C; 152-153 C; and 222-224 C, respectively left to right).
C''N ~",.
CN ~ CN
CN CN
Bu
Example 4: Preparation of trans-[(N,N-di(2-ethanol)amino)phenylene-3-decanyl-2-
thiophene]
To a solution of 3-decanyl-2-methyltributylphosphonium-thiophene bromide (26
g, 0.05 mol) and N,N-di-ethanol aminophenyl aldehyde (12.6 g, 0.06 mol) in 200
ml of
ethanol, NaOCaHS (1 M in ethanol) was added dropwise. The resulting mixture
was
refluxed for 98 hours. After removal of this reaction from the bath oil, the
solvent was
evaporated, and the residue was extracted with ethyl ether (3 x 150 ml). The
combined
ether mixture was washed with water ( 100 ml), brine (2 x 100 ml) and dried
over
2o anhydrous MgS04. After removal of the solvent, the residue was purified by
column
chromatography on silica and eluted using 50% ethyl acetate, 10% acetone, and
40%
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33
hexane to give the pure title compound with a yield of 16 g. Carbon and proton
NMR
were consistent with the structure.
Example 5: Preparation of trans-[(N,N-di(2-ethanol)amino)phenylene-2-thiene-3-
decanyl-5-al]
To a 500 ml flask with the compound synthesized above ( 10.44 g, 0.0243 mol),
200 ml of THF was added. The solution was cooled to -78 C and n-BuLi (32 ml,
2.5 M in
hexane) was added dropwise. The mixture was stirred for 2 hours followed by
addition of
DMF (6 ml). The resulting solution was stirred overnight at room temperature.
After
adding HCl (2 M, 50 ml) and stirring for an hour, the THF was evaporated. The
residue
was extracted with ethyl ether (3 x 100 ml). The combined organic solution was
washed
with saturated Na2C03 solution (50 ml), water ( 100 ml), brine ( 100 ml) and
dried over
anhydrous MgS04. After evaporating the solvent, solid target compound (I1.1 g,
mp 107-
109 C) was obtained. HNMR showed that this compound was pure enough for the
next
step.
Example 6: Preparation of Chromophore
The above aldehyde compound (3 g, 6.54 mmol) and 2-dicyanomethylen-3-
2o cyano-4,5-dimethyl-5-(3,4-dichlorophenyl)-2,5-dihydrofuran (2.4 g, 7.27
mmol) were
mixed and dissolved in EtOH (30 ml). Two or three drops of piperidine were
added. The
mixture was refluxed for 48 hours. After cooling, the precipitated solid was
filtered,
recrystalized from EtOH, and purified by chromatography silica elution solvent
to give
3.38 g of the chromophore. Carbon and proton NMR were performed and analysis
thereof
was consistent with the structure.
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Example 7: Preparation of Chromophore
Traps-[(N,N-di(2-ethanol)amino)phenylene-3,4-dibutyl-2-thiophene-5-al] (0.3 g,
0.7 mmol) is mixed with 2-dicyanomethylen-3-cyano-4,5-dimethyl-5-(3,4
dichlorophenyl)-2,5-dihydrofurane (0.23 g, 0.7 mmol) in EtOH (20 ml). Two or
three
drops of piperidine is added. The mixture is refluxed for 48 hours. After
cooling, the
precipitated solid is filtered, recrystalized from EtOH, and purified by
chromatography
silica elution solvent.
Example 8: Preparation of Highly Chlorinated Electro-Optic Polymer
To a three-neck flask with 1,4,5,6,7,7-hexchloro-5-norbornene-2,3-dicarboxylic
acid chloride (2.65 g, 6.23 mmol) and 2,3,5,6-tetrachloro-p-xylene-aa-diol
(1.36 g, 4.93
mmol), 2-dicyanomethylen-3-cyano-4-{2-[E-(4-N,N-di-(2-ethanol)amino)phenylene-
(3-
decanyl)thien-5]-E-vinyl}-5-methyl-5-(3,4-dichlorophenyl)-2,5-dihydrofuran (1
g, 1.3
mmol) were mixed in 20 ml THF at 70 C. Et3N (1.26 g in 15 ml THF) was added
dropwise. The mixture was refluxed under Ar for 48 hours. After evaporating
some of the
THF, the rest of the solution was slowly dropped into MeOH (300 ml) and water
(50 ml)
with violent stirring. The precipitated solid was filtered, redissolved in THF
and
precipitated again in MeOH (300 ml). The collected solid was vacuum dried for
8 hours
and weighed 4.5 g. The polymer was characterized by DSC and TGA. The Tg is 152
C,
2o and the decomposing temperature under air is 285 C.
Although the invention has been described in detail for the purpose of
illustration,
it is understood that such detail is solely for that purpose, and variations
can be made
therein by those skilled in the art without departing from the spirit and
scope of the
invention which is defined by the following claims.
