U.S. patent application number 14/095708 was filed with the patent office on 2014-10-09 for electro-optic polymer and electro-optic devices made therefrom.
This patent application is currently assigned to GIGOPTIX, INC.. The applicant listed for this patent is GIGOPTIX, INC.. Invention is credited to BAOQUAN CHEN, HUI CHEN, DIYUN HUANG, DANLIANG JIN, GUOMIN YU.
Application Number | 20140302250 14/095708 |
Document ID | / |
Family ID | 45832244 |
Filed Date | 2014-10-09 |
United States Patent
Application |
20140302250 |
Kind Code |
A1 |
CHEN; BAOQUAN ; et
al. |
October 9, 2014 |
ELECTRO-OPTIC POLYMER AND ELECTRO-OPTIC DEVICES MADE THEREFROM
Abstract
According to an embodiment, an electro-optic polymer comprises a
host polymer and a guest nonlinear optical chromophore having the
structure D-.pi.-A, wherein: D is a donor, .pi. is a .pi.-bridge,
and A is an acceptor; a bulky substituent group is covalently
attached to at least one of D, .pi., or A; and the bulky
substituent group has at least one non-covalent interaction with
part of the host polymer that impedes chromophore depoling.
Inventors: |
CHEN; BAOQUAN; (KENMORE,
WA) ; JIN; DANLIANG; (BOTHELL, WA) ; YU;
GUOMIN; (KENMORE, WA) ; CHEN; HUI; (KIRKLAND,
WA) ; HUANG; DIYUN; (WATERTOWN, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GIGOPTIX, INC. |
SAN JOSE |
CA |
US |
|
|
Assignee: |
GIGOPTIX, INC.
SAN JOSE
CA
|
Family ID: |
45832244 |
Appl. No.: |
14/095708 |
Filed: |
December 3, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12959898 |
Dec 3, 2010 |
8618241 |
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14095708 |
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12270714 |
Nov 13, 2008 |
7902322 |
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12959898 |
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61003443 |
Nov 15, 2007 |
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Current U.S.
Class: |
427/504 ;
252/586 |
Current CPC
Class: |
G02F 2202/022 20130101;
C09K 2211/1425 20130101; C09K 9/02 20130101; G02F 1/3615 20130101;
G02F 1/3611 20130101; C09K 2211/1088 20130101; G02F 1/3558
20130101; G02F 1/3614 20130101; C09K 2211/1092 20130101; C09K
2211/1096 20130101; C09K 2211/1416 20130101; C09K 2211/1022
20130101 |
Class at
Publication: |
427/504 ;
252/586 |
International
Class: |
G02F 1/355 20060101
G02F001/355 |
Goverment Interests
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] The inventions disclosed herein were made the U.S.
Government support pursuant to NRO Contract No. NRO000-07-C-0123
and DARPA Contract No. W31P4Q-08-C-0198. Accordingly, the
Government may have certain rights in the inventions disclosed
herein.
Claims
1.-36. (canceled)
37. An electro-optic polymer, comprising: a host polymer including
host aryl groups; and a guest nonlinear optical chromophore having
the structure D-.pi.-A, wherein D is an electron donor, .pi. is an
electronically conjugated bridge electronically conjugated to D,
and A is an electron acceptor electronically conjugated to .pi. and
configured to exchange electron density with D through p-orbital
electrons of .pi.; wherein the guest chromophore includes at least
two guest aryl substituent groups covalently bound to the
chromophore; wherein each guest aryl substituent group is
configured to non-covalently interact with one or more host aryl
groups.
38. The electro-optic polymer of claim 37, wherein the chromophore
is configured to be electrically poled into an alignment; and
wherein the non-covalent interaction between each guest aryl
substituent group and one or more host aryl groups is configured to
impede chromophore depoling.
39. The electro-optic polymer of claim 37, wherein the chromophore
is poled; and wherein the non-covalent interaction between at least
a portion of the guest aryl substituent groups and one or more host
aryl groups impedes chromophore depoling.
40. The electro-optic polymer of claim 37, wherein at least one of
the guest aryl substituent groups is covalently bound to .pi..
41. The electro-optic polymer of claim 40, wherein at least one of
the guest aryl substituent groups is covalently bound to D.
42. The electro-optic polymer of claim 40, wherein at least one of
the guest aryl substituent groups is covalently bound to A.
43. The electro-optic polymer of claim 37, wherein the at least two
guest aryl substituent groups each include a triaryl group.
44. The electro-optic polymer of claim 43, wherein the triaryl
group has the structure ##STR00018## wherein: D is a donor; .pi. is
a p-bridge; A is an acceptor; X is a substituent center; Ar.sup.1,
Ar.sup.2, and Ar.sup.3 are the aryl groups; and L is a covalent
linker attached to the chromophore.
45. The electro-optic polymer of claim 44, wherein the substituent
centers include a carbon atom or a silicon atom.
46. The electro-optic polymer of claim 37, wherein the two guest
aryl groups comprise: an aryl ring, polycyclic aryl group,
heterocyclic aryl group, or a polyheterocyclic aryl group.
47. The electro-optic polymer of claim 37, wherein the host polymer
consists essentially of: a polysulfone; a polyester; a
polycarbonate; a polyimide; a polyimideester; a polyarylether; a
poly(methacrylic acid ester); a poly(ether ketone); a
polybenzothiazole; a polybenzoxazole; a polybenzobisthiazole; a
polybenzobisoxazole; a poly(aryl oxide); a polyetherimide; a
polyfluorene; a polyarylenevinylene; a polyquinoline, a
polyvinylcarbazole; or any copolymer thereof.
48. The electro-optic polymer of claim 37, wherein each guest aryl
substituent group is configured to non-covalently interact with one
or more host aryl groups via a physical interaction.
49. The electro-optic polymer of claim 48, wherein the physical
interaction includes a physical interaction corresponding to a van
der Waals force.
50. The electro-optic polymer of claim 49, wherein the van der
Waals force includes at least one of a Keesom, Debye, or London
force.
51. The electro-optic polymer of claim 48, wherein each guest aryl
substituent group is configured to non-covalently interact with one
or more host aryl groups via a pi-interaction, a size interaction,
or a preorganized binding interaction.
52. An electro-optic device comprising the electro-optic polymer of
claim 37.
53. The electro-optic device of claim 52, wherein the electro-optic
device includes a Mach-Zehnder interferometer, a Michelson
interferometer, a micro-ring resonator, or a directional
coupler.
54. An electro-optic device, comprising: an electro-optic waveguide
core comprising an electro-optic polymer; and a clad polymer having
a refractive index lower than the electro-optic waveguide core;
wherein: the electro-optic polymer comprises: a host polymer
including host aryl groups; and a guest nonlinear optical
chromophore having the structure D-.pi.-A, wherein D is an electron
donor, .pi. is an electronically conjugated bridge electronically
conjugated to D, and A is an electron acceptor electronically
conjugated to .pi. and configured to exchange electron density with
D through p-orbital electrons of .pi.; wherein the guest
chromophore includes at least two guest aryl substituent groups
covalently bound to the chromophore; wherein each guest aryl
substituent group is configured to non-covalently interact with one
or more host aryl groups.
55. The electro-optic device of claim 54, wherein the electro-optic
device comprises: a Mach-Zehnder interferometer, a Michelson
interferometer, a micro-ring resonator, or a directional
coupler.
56. The electro-optic device of claim 54, wherein at least one of
the guest aryl substituent groups is covalently bound to .pi..
57. The electro-optic device of claim 56, wherein at least one of
the guest aryl substituent groups is covalently bound to D.
58. The electro-optic device of claim 56, wherein at least one of
the guest aryl substituent groups is covalently bound to A.
59. The electro-optic device of claim 54, wherein the at least two
guest aryl substituent groups each include a triaryl group.
60. A method for making an electro-optic device, comprising:
providing a precursor for a host polymer, the precursor for the
host polymer comprising guest aryl groups; providing a guest
optical chromophore, the guest chromophore comprising: the
structure D-.pi.-A, wherein D is an electron donor, .pi. is an
electronically conjugated bridge electronically conjugated to D,
and A is an electron acceptor electronically conjugated to .pi. and
configured to exchange electron density with D through p-orbital
electrons of .pi.; and at least two guest aryl substituent groups
covalently bound to the chromophore; mixing the precursor for the
host polymer with the guest chromophore to form a precursor for an
electro-optic polymer; depositing the precursor for the
electro-optic polymer on a substrate; and poling the electro-optic
polymer to cause the guest chromophore to align while causing the
host polymer portion of the electro-optic polymer to polymerize to
form the electro-optic polymer.
61. The method for making an electro-optic device of claim 60,
wherein at least a portion of the guest aryl substituent groups
non-covalently interact with at least a portion of the host aryl
groups to inhibit depoling of the guest chromophore in
electro-optic polymer.
62. The method for making an electro-optic device of claim 60,
wherein providing a precursor for a host polymer comprises
providing a precursor for a polysulfone; a polyester; a
polycarbonate; a polyimide; a polyimideester; a polyarylether; a
poly(methacrylic acid ester); a poly(ether ketone); a
polybenzothiazole; a polybenzoxazole; a polybenzobisthiazole; a
polybenzobisoxazole; a poly(aryl oxide); a polyetherimide; a
polyfluorene; a polyarylenevinylene; a polyquinoline, a
polyvinylcarbazole; or any copolymer thereof.
63. The method for making an electro-optic device of claim 60,
wherein at least one of the guest aryl substituent groups is
covalently bound to .pi..
64. The method for making an electro-optic device of claim 63,
wherein at least one of the guest aryl substituent groups is
covalently bound to D.
65. The method for making an electro-optic device of claim 63,
wherein at least one of the guest aryl substituent groups is
covalently bound to A.
66. The method for making an electro-optic device of claim 60,
wherein the at least two guest aryl substituent groups each include
a triaryl group.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Continuation of and claims priority
from U.S. application Ser. No. 12/959,898, entitled "STABILIZED
ELECTRO-OPTIC MATERIALS AND ELECTRO-OPTIC DEVICES MADE THEREFROM",
filed Dec. 3, 2010, at the time of this filing; which is a
Continuation-in-Part from U.S. patent application Ser. No.
12/270,714, entitled NONLINEAR OPTICAL CHROMOPHORES WITH
STABILIZING SUBSTITUENT AND ELECTRO-OPTIC DEVICES, filed Nov. 13,
2008, now U.S. Pat. No. 7,902,322, issued on Mar. 8, 2011; which
claims priority benefit from U.S. Provisional Patent Application
Ser. No. 61/003,443, entitled NONLINEAR OPTICAL CHROMOPHORES WITH
STABILIZING SUBSTITUENT AND ELECTRO-OPTIC DEVICES, filed Nov. 15,
2007; U.S. Provisional Patent Application Ser. No. 61/315,797,
entitled ELECTRO-OPTIC CHROMOPHORE MATERIAL AND DEVICES WITH
ENHANCED STABILITY, filed Mar. 19, 2010; and U.S. Provisional
Patent Application Ser. No. 61/383,282, entitled ELECTRO OPTIC
CHROMOPHORE AND HOST POLYMER SYSTEM FOR INTEGRATED CIRCUIT
COMMUNICATION, filed Sep. 15, 2010, each of which, to the extent
not inconsistent with the disclosure herein, is incorporated by
reference.
BACKGROUND
[0003] Nonlinear optical chromophores provide the electro-optic
(EO) activity in poled, electro-optic polymer devices.
Electro-optic polymers have been investigated for many years as an
alternative to inorganic materials such as lithium niobate in
electro-optic devices. Electro-optic devices may include, for
example, external modulators for telecom, RF photonics, and optical
interconnects and so forth. High electro-optic activity and the
stability of electro-optic activity, which is also referred to as
"temporal stability", are important for commercially viable
devices. Electro-optic activity may be increased in electro-optic
polymers by increasing the concentration of nonlinear optical
chromophores and by increasing of the electro-optic property of
chromophores. However, some techniques for increasing chromophore
concentration may decrease temporal stability.
OVERVIEW
[0004] One embodiment is an electro-optic polymer comprising a host
polymer and a guest nonlinear optical chromophore having the
structure D-.pi.-A, wherein: D is a donor, .pi. is a .pi.-bridge,
and A is an acceptor; a bulky substituent group is covalently
attached to at least one of D, .pi., or A; and the bulky
substituent group has at least one non-covalent interaction with
part of the host polymer that impedes chromophore depoling.
[0005] One embodiment is an electro-optic polymer comprising a
poled nonlinear optical chromophore and a host polymer, wherein the
nonlinear optical chromophore is substituted with two or more bulky
groups and the host polymer is configured to cooperate with the
bulky groups to impede chromophore depoling.
[0006] One embodiment is a nonlinear optical chromophore having the
structure D-.pi.-A, wherein D is a donor, .pi. is a .pi.-bridge,
and A is an acceptor, and wherein at least one of D, .pi., or A is
covalently attached to a substituent group including a substituent
center that is directly bonded to at least three aryl groups.
[0007] Another embodiment is an electro-optic polymer including a
nonlinear optical chromophore having the structure D-.pi.-A,
wherein D is a donor, .pi. is a .pi.-bridge, A is an acceptor, and
at least one of D, .pi., or A is covalently attached to a
substituent group including a substituent center that is directly
bonded to an aryl group, and wherein the electro-optic polymer has
greater temporal stability than when an alkyl group is substituted
for the aryl group. According to embodiments, a plurality of aryl
groups may be directly bonded to the substituent center.
[0008] Another embodiment is a method, including a) providing a
polymer including a nonlinear optical chromophore having the
structure D-.pi.-A, wherein D is a donor, .pi. is a .pi.-bridge, A
is an acceptor, and at least one of D, .pi., or A is covalently
attached to a substituent group including a substituent center that
is directly bonded to at least one aryl group; and b) poling the
polymer to form and electro-optic polymer, wherein the
electro-optic polymer has greater temporal stability than when an
alkyl group is substituted for the aryl group.
[0009] Other embodiments include electro-optic devices including
the nonlinear optical chromophores and electro-optic polymers.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 illustrates nonlinear optical chromophores according
to embodiments.
[0011] FIG. 2 illustrates the synthesis of a chromophore according
to an embodiment.
[0012] FIG. 3 illustrates the synthesis of a chromophore according
to an embodiment.
[0013] FIG. 4 illustrates the synthesis of chromophores according
to an embodiment.
[0014] FIG. 5 illustrates a donor and a synthetic scheme for
chromophore having the donor according to an embodiment.
[0015] FIG. 6 illustrates polymers according to an embodiment.
[0016] FIGS. 7A-7D illustrate Jonscher analyses of temporal
stability, according to an embodiment.
[0017] FIGS. 8A and 8B illustrate hyperbolic tangent model analyses
of temporal stability, according to an embodiment.
[0018] FIG. 9 illustrates Jonscher analyses of temporal stability,
according to an embodiment.
[0019] FIG. 10 illustrates fabrication steps for a polymer
modulator, according to an embodiment.
[0020] FIG. 11 illustrates a Mach-Zehnder interferometer and
electrodes, according to an embodiment.
[0021] FIG. 12 illustrates a cross section of a polymer modulator
stack, according to an embodiment.
[0022] FIGS. 13A and 13B illustrate long temporal stability of a
polymer modulator, according to an embodiment.
[0023] FIGS. 14A and 14B illustrate pi-interactions according to
some embodiments.
[0024] FIGS. 15A-15D illustrate pi-interactions according to some
embodiments.
DETAILED DESCRIPTION
[0025] In the following detailed description, reference is made to
the accompanying drawings, which form a part hereof. In the
drawings, similar symbols typically identify similar components,
unless context dictates otherwise. The illustrative embodiments
described in the detailed description and drawings are not meant to
be limiting. Other embodiments may be utilized, and other changes
may be made, without departing from the spirit or scope of the
subject matter presented here.
[0026] According to an embodiment, an organic chromophore includes
aryl substituents. The aryl substituents may provide additional
steric bulk to the chromophores and allow higher concentrations of
the chromophores. The aryl substituents may also provide thermal,
temporal, and/or other stability enhancements.
[0027] One embodiment is a second order nonlinear optical
chromophore having the structure D-.pi.-A, wherein D is a donor,
.pi. is a .pi.-bridge, and A is an acceptor, and wherein at least
one of D, .pi., or A is covalently attached to a substituent group
including a substituent center that is directly bonded to at least
two aryl groups, preferably three aryl groups. What is meant by
terms such as donor, .pi.-bridge, and acceptor; and general
synthetic methods for forming D-.pi.-A chromophores are known in
the art, see for example U.S. Pat. No. 6,716,995, incorporated by
reference herein.
[0028] A donor (represented in chemical structures by "D" or
"D.sup.n" where n is an integer) includes an atom or group of atoms
that has a low oxidation potential, wherein the atom or group of
atoms can donate electrons to an acceptor "A" through a
.pi.-bridge. The donor (D) has a lower electron affinity that does
the acceptor (A), so that, at least in the absence of an external
electric field, the chromophore is generally polarized, with
relatively less electron density on the donor (D). Typically, a
donor group contains at least one heteroatom that has a lone pair
of electrons capable of being in conjugation with the p-orbitals of
an atom directly attached to the heteroatom such that a resonance
structure can be drawn that moves the lone pair of electrons into a
bond with the p-orbital of the atom directly attached to the
heteroatom to formally increase the multiplicity of the bond
between the heteroatom and the atom directly attached to the
heteroatom (i.e., a single bond is formally converted to double
bond, or a double bond is formally converted to a triple bond) so
that the heteroatom gains formal positive charge. The p-orbitals of
the atom directly attached to the heteroatom may be vacant or part
of a multiple bond to another atom other than the heteroatom. The
heteroatom may be a substituent of an atom that has pi bonds or may
be in a heterocyclic ring. Exemplary donor groups include but are
not limited to R.sub.2N-- and, R.sub.nX.sup.1--, where R is alkyl,
aryl or heteroaryl, X.sup.1 is O, S, P, Se, or Te, and n is 1 or 2.
The total number of heteroatoms and carbons in a donor group may be
about 30, and the donor group may be substituted further with
alkyl, aryl, or heteroaryl. The "donor" and "acceptor" terminology
is well known and understood in the art. See, e.g., U.S. Pat. Nos.
5,670,091, 5,679,763, and 6,090,332.
[0029] An acceptor (represented in chemical structures by "A" or
"A.sup.n" where n is an integer) is an atom or group of atoms that
has a low reduction potential, wherein the atom or group of atoms
can accept electrons from a donor through a .pi.-bridge. The
acceptor (A) has a higher electron affinity that does the donor
(D), so that, at least in the absence of an external electric
field, the chromophore is generally polarized, with relatively more
electron density on the acceptor (D). Typically, an acceptor group
contains at least one electronegative heteroatom that is part of a
pi bond (a double or triple bond) such that a resonance structure
can be drawn that moves the electron pair of the pi bond to the
heteroatom and concomitantly decreases the multiplicity of the pi
bond (i.e., a double bond is formally converted to single bond or a
triple bond is formally converted to a double bond) so that the
heteroatom gains formal negative charge. The heteroatom may be part
of a heterocyclic ring. Exemplary acceptor groups include but are
not limited to --NO.sub.2, --CN, --CHO, COR, CO.sub.2R,
--PO(OR).sub.3, --SOR, --SO.sub.2R, and --SO.sub.3R where R is
alkyl, aryl, or heteroaryl. The total number of heteroatoms and
carbons in an acceptor group is about 30, and the acceptor group
may be substituted further with alkyl, aryl, and/or heteroaryl. The
"donor" and "acceptor" terminology is well known and understood in
the art. See, e.g., U.S. Pat. Nos. 5,670,091, 5,679,763, and
6,090,332.
[0030] A ".pi.-bridge" or "electronically conjugated bridge"
(represented in chemical structures by ".pi." or ".pi..sup.n" where
n is an integer) includes an atom or group of atoms through which
electrons may be delocalized from an electron donor (defined above)
to an electron acceptor (defined above) through the orbitals of
atoms in the bridge. Such groups are very well known in the art.
Typically, the orbitals will be p-orbitals on double (sp.sup.2) or
triple (sp) bonded carbon atoms such as those found in alkenes,
alkynes, neutral or charged aromatic rings, and neutral or charged
heteroaromatic ring systems. Additionally, the orbitals may be
p-orbitals on atoms such as boron or nitrogen. Additionally, the
orbitals may be p, d or f organometallic orbitals or hybrid
organometallic orbitals. The atoms of the bridge that contain the
orbitals through which the electrons are delocalized are referred
to here as the "critical atoms." The number of critical atoms in a
bridge may be a number from 1 to about 30. The critical atoms may
be substituted with an organic or inorganic group. The substituent
may be selected with a view to improving the solubility of the
chromophore in a polymer matrix, to enhancing the stability of the
chromophore, or for other purpose.
[0031] The substituent group (or any of multiple substituent
groups) may be covalently attached to one or more of D, .pi., and A
through a variety of linkages including single bonds, single atoms,
heteroatoms, metal atoms (e.g., organometallics), aliphatic chains,
aryl rings, functional groups, or combinations thereof. The
substituent center may have multiple atoms (e.g., an aryl or
aliphatic ring), may be a single atom (e.g., a carbon, silicon, or
metal atom), or may be a combination thereof (e.g., a ring system
where one aryl group is bonded to one atom of the ring system and
the other two aryl groups are bonded to another atom in the ring
system).
[0032] For example, in some embodiments the substituent center
includes a carbon atom, a heteroatom, or a metal atom. In other
embodiments, the substituent center may be a carbon atom, a silicon
atom, a tin atom, a sulfur atom, a nitrogen atom, or a phosphorous
atom. In an embodiment, the substituent center may be a 3-, 4-, 5-,
or 6-membered ring like a benzene ring, thiophene ring, furan ring,
pyridine ring, imidazole ring, pyrrole ring, thiazole ring, oxazole
ring, pyrazole ring, isothiazole ring, isooxazole ring, or triazole
ring.
[0033] The aryl groups bonded to the substituent center may be
further substituted with alkyl groups, heteroatoms, aryl groups, or
a combination thereof. For example, in some embodiments, the aryl
groups may, independently at each position, comprise a phenyl ring,
a naphthyl ring, a biphenyl group, a pyridyl ring, a bipyridyl
group, thiophene group, furan group, imidazole group, pyrrole
group, thiazole group, oxazole group, pyrazole group, isothiazole
group, isooxazole group, triazole group or an anthracenyl
group.
[0034] In an embodiment, the substituent group includes the
structure:
##STR00001##
wherein: X is the substituent center; Ar.sup.1, Ar.sup.2, and
Ar.sup.3 are the aryl groups; and L is a covalent linker attached
to D, .pi., or A. According to various embodiments, X may be C, Si,
N, B, Sn, S, S(O), SO.sub.2, P(O) (phosphine oxide), P (phosphine),
or an aromatic ring of any kind. In some embodiments, Ar.sup.1,
Ar.sup.2, and Ar.sup.3 each independently include a substituted or
un-substituted phenyl ring, a substituted or un-substituted benzyl
ring, a substituted or un-substituted naphthyl ring, a substituted
or un-substituted biphenyl group, a substituted or un-substituted
pyridyl ring, a substituted or un-substituted bipyridyl group, a
substituted or un-substituted thiophene ring, a substituted or
un-substituted benzothiophenene ring, a substituted or
un-substituted imidazole ring, a substituted or un-substituted
thiozale ring, substituted or un-substituted thienothiophene group,
substituted or un-substituted a substituted or un-substituted
quinoline group, or a substituted or un-substituted anthracenyl
group. In some embodiments, L includes the structure:
##STR00002##
wherein: R.sup.1 is independently at each occurrence an H, an alkyl
group, or a halogen; Y.sup.1 is --C(R.sup.1).sub.2--, O, S,
--N(R.sup.1)--N(R.sup.1)C(O)--, --C(O).sub.2--, --C.sub.6H.sub.6--,
or --OC.sub.6H.sub.6--, thiophenyl, n is 0-6; and m is 1-3.
[0035] Electro-optic polymers including these nonlinear optical
chromophores may show high electro-optic coefficient. The temporal
stability is significantly increased compared to electro-optic
polymers including chromophores where alkyl groups are substituted
for the aryl groups, where the aryl groups have .pi.(pi)-.pi.(pi)
interactions (also referred to herein as pi interactions) between
aryl bulky groups on the chromophore and aryl groups on polymer. In
this context, the symbol ".pi." may be used generally to refer to a
system of one or more multiple bonds, linear or cyclic, as is known
on the art instead of in the context of representing the conjugated
.pi.-bridge of a chromophore. The aryl groups may be sterically
larger than the alkyl groups. The pi-interactions between the aryl
bulky group/s on the chromophore and the aryl groups on the polymer
may be enhanced by complementary geometric dispositions of the aryl
groups that enhance the pi interactions (e.g., aryl groups
tetrahedrally disposed around a substituent center in the
chromophore bulky group may favorably pi-interact (e.g., stack)
more efficiently with aryl groups tetrahedrally disposed around a
carbon in the polymer backbone).
[0036] Donors, acceptors, and .pi.-bridge moieties may include
functional groups that may be covalently bonded to the L group.
[0037] According to embodiments, D includes:
##STR00003## ##STR00004##
.pi. includes:
##STR00005## ##STR00006##
and A includes:
##STR00007##
wherein: R.sup.1, independently at each occurrence is H, an
aliphatic group such as an alkyl or alkoxy group, or an aryl group.
R.sup.2, independently at each occurrence, is an alkyl group, a
halogenated alkyl group, a halogenated aryl group, or an aryl group
with or without substitutions; Z is a single bond, --CH.dbd.CH--,
--C.ident.C--, --N.dbd.N--, or --N.dbd.CH--; Y.sup.2, independently
at each occurrence, is CH.sub.2, O, S, N(R.sup.1), Si(R.sup.1),
S(O), SO.sub.2, --CH(R.sup.1)-- or --C(R.sup.1).sub.2--; R.sup.3
independently at each occurrence is a cyano group, a nitro group,
an ester group, or a halogen; and at least one R.sup.1, R.sup.2, or
R.sup.3 includes the substituent group. m is 1-6 and n is 1-4, In
another embodiment, D has one of the structures:
##STR00008##
wherein X is a substituent center; Ar.sup.1, Ar.sup.2, Ar.sup.3,
Ar.sup.4, Ar.sup.5, and Ar.sup.6 are aryl groups; Ar.sup.7 is a
conjugated aromatic group; R.sup.1 of D independently at each
occurrence is H, an alkyl group, a heteroalkyl group, an aryl
group, or a hetero aryl group; p is 2-6; I is 0-2; m is 1-3; and n
is 1-3; .pi. has the structure:
##STR00009##
and wherein R.sup.1 of n independently comprises
##STR00010##
or is H, an alkyl group, a heteroalkyl group, an aryl group, or a
hetero aryl group; L is a covalent linker; z is 1,2-vinylene,
1,4-phenylene, or 2,5-thiophenylene, Y.sup.2 is S, O or
SiR.sup.2.sub.2, where R.sup.2 is aliphatic group, and m is 1-3. In
some embodiments, X is C or Si
[0038] In another embodiment, .pi. includes:
##STR00011##
and A is:
##STR00012##
[0039] wherein: R.sup.1 is independently at each occurrence an H,
an alkyl group, or a halogen; Z is a single bond or --CH.dbd.CH--;
Y.sup.2 is O, S, --C(R.sup.1).sub.2--; R.sup.2 is independently at
each occurrence an alkyl group or an aryl group; and m=1-3. In
embodiments, the nonlinear optical chromophore includes one of the
structures shown in FIG. 1 wherein X, R.sup.1, and R.sup.2 may be
as described above. In another embodiment, A has the structure:
##STR00013##
wherein: R.sup.2, independently at each occurrence is H, an
aliphatic group such as a branched or un-branched alkyl or alkoxy
group, or a substituted or un-substituted aryl group. R.sup.3,
independently at each occurrence, is cyano, CF.sub.3, nitro group,
an ester group, a halogen, or an substituted or un-substituted aryl
group; Y.sup.2, is CH.sub.2, O, S, N(R.sup.2), Si(R.sup.2).sub.2 or
--C(R.sup.2).sub.2--. In another embodiment, at least one R.sup.1
of .pi. comprises
##STR00014##
[0040] According to an embodiment, a nonlinear optical chromophore
has the structure D-.pi.-A, wherein D is a donor, .pi. is a
.pi.-bridge, and A is an acceptor; and wherein at least one of D,
.pi., or A is covalently attached to a substituent group including
at least one of:
##STR00015##
[0041] and wherein: X is C or Si; Y.sup.1 is --C(R.sup.1).sub.2--,
O, S, --N(R.sup.1)--, --N(R.sup.1)C(O)--, --C(O).sub.2--; Y.sup.3
is N or P; and Ar.sup.1, Ar.sup.2, and Ar.sup.3 are aryl groups.
The aryl groups, D, .pi., and A may be, as described above for
example.
[0042] Other embodiments include electro-optic composites and
polymers including one or more of the nonlinear optical
chromophores described above. Typically, the polymer is poled with
an electric field to induce electro-optic activity. Other
techniques such as self-organization or photo-induced poling may
also be used. The nonlinear optical chromophore may be covalently
attached to the polymer matrix (e.g., as in a side-chain polymer or
a crosslinked polymer) or may be present as a guest in a polymer
matrix host (e.g., a composite material). The nonlinear chromophore
may also be present as guest in the polymer matrix and then be
covalently bonded or crosslinked to the matrix before, during, or
after poling. Polymers that may be used as a matrix include, for
example, polycarbonates, poly(arylene ether)s, polysulfones,
polyimides, polyesters, polyacrylates, and copolymers thereof.
[0043] In some embodiments, bulky groups on the chromophore are
used to change the Tg and to reduce the optical loss of
electro-optic (EO) polymers by changing the physical interaction
between polymer host and chromophore guest. We found that the
physical interaction between host polymer and guest molecular can
be increased by selecting specific chemical structure of the
isolating (e.g., bulky) group on the chromophore. Physical
interactions may include, for example, pi-pi interactions, size
interactions that block chromophore movement significantly below Tg
(e.g., there is not enough free volume in the polymer composite at
Tg for translation of the bulky group, and hence the chromophore,
which is generally required for chromophore relaxation), and
preorganized binding interactions where the bulky groups fit
preferentially into conformationally defined spaces in the polymer,
or any combination thereof. In some embodiment, the physical
interactions are controlled or supplemented by van der Waals forces
(e.g., Keesom, Debye, or London forces) among the moiety of the
bulky groups and aryl groups on polymer chains. Such non-covalent
interactions may increase temporal stability below Tg and decrease
optical loss while improving chromophore loading density and
avoiding the deleterious effects of crosslinking on the degree of
poling-induced alignment.
[0044] Pi-pi interactions are known in the art and may include
interaction, for example, between a pi-system and another pi-system
(e.g., an aromatic, a heteroaromatic, an alkene, an alkyne, or
carbonyl function), a partially charged atoms or groups of atoms
(e.g., --H in a polar bond, --F), or a fully charged atom or groups
of atoms (e.g., --NR(H).sub.3.sup.+, --BR(H).sub.3.sup.-).
pi-interaction may increase affinity of the chromophore guest for
the polymer host and increase energy barriers to chromophore
movement, which is generally required for chromophore relaxation
and depoling. In some embodiments, pi-interactions may be used to
raise the Tg of a polymer (e.g., by increasing interactions between
polymer chains) or the Tg of a polymer composite (e.g., by
increasing interactions between the polymer host and the
chromophore guest). In some embodiments, the pi-interactions of the
bulky groups increase the Tg of the polymer composite compared to
when pi-interacting moieties on the bulky groups are replaced with
moieties that have no or weak pi-interactions. In some embodiments,
pi-interacting groups on the chromophore are chosen to interact
preferentially with pi-interacting groups on the polymer chain.
Such preferential interactions may include, for example,
pi-interacting donors/acceptors on the bulky group with
complementary pi-interacting acceptors/donors of the polymer chain,
or spatial face-to-face and/or edge-to-face interactions between
pi-interacting groups on the chromophores and polymer chains, or
any combination thereof. In some embodiments, multiple interactions
such as a face-to-face and face-to-edge between one or multiple
moieties on the chromophore bulky group with multiple or one
moieties on the polymer chain may increase interaction strength and
temporal stability. The pi-interactions between the aryl bulky
group/s on the chromophore and the aryl groups on the polymer may
be enhanced by complementary geometric dispositions of the aryl
groups that enhance the pi interactions (e.g., aryl groups
tetrahedrally disposed around a substituent center in the
chromophore bulky group may favorably pi-interact (e.g., stack)
more efficiently with aryl groups tetrahedrally disposed around a
carbon in the polymer backbone as shown in a top view (FIG. 14A)
and the side view (FIG. 14B, with partial pi-interactions shown)
from rotating 90.degree. around the x-axis). In other embodiments,
the polymer may be chosen because the chain adopts certain
conformations and spatial distributions (e.g., preorganization) of
pi-interacting groups that favor face-to-face (FIG. 15A) or
face-to-edge (FIG. 15B) interactions with the pi-interacting groups
on the chromophore. Some embodiments may have multiple face-to-face
interactions between pi-interacting groups on the polymer and the
chromophore (e.g., FIG. 15C) or a combination of face-to-face and
face-to-edge pi-interactions (e.g., FIG. 15D). In other
embodiments, pi-interacting donors generally have electron rich
p-systems or orbitals and pi-interacting acceptors generally have
electron poor p-systems or orbitals. In some embodiments, the bulky
groups on the chromophore have pi-interacting donors or
pi-interacting acceptors that are complimentary to pi-interacting
acceptors or pi-interacting donors on the polymer chain. In some
embodiments, such pi-interacting acceptors may include, for
example, heterocycles such as pyridines, pyrazines, oxadiazoles,
etc, and pi-interacting donors may include, for example,
heterocycles such as thiophene, furan, carbazole, etc. The
pi-interacting donors/acceptors may also include aryl groups that
are electron rich/poor from electron donating/withdrawing
substituents. In some embodiments, the bulky group includes at
least one pi-interacting acceptor complementary to a pi-interacting
donor on the polymer chain. In some embodiments, the bulky group
includes at least one pi-interacting donor complementary to a
pi-interacting acceptor on the polymer chain.
[0045] In some embodiments, the size of the bulky groups prevents
translation/depoling of the chromophore in the polymer free volume
significantly (e.g., 20.degree. C.) below the Tg of the composite.
In some embodiments, the bulky group is substantially 3-dimensional
(e.g., the bulky group has bulk-forming moieties tetrahedrally or
trigonal bipyramidally disposed around a substituent center atom
rather than having a substantially planar or linear arrangement of
the bulk-forming moieties around the substituent center atom). Such
3-dimensionality may reduce the possibility of the bulky group, and
hence the chromophore, form translating through free volume
compared to a planar or linear bulky group. The bulk-forming groups
may independently comprise, for example, and an organic moiety
having 5 or more carbon atoms. In some embodiments, the
bulk-forming groups may independently comprise conformationally
rigidified structures such as rings. The rings may be aliphatic,
aromatic, or any combination thereof. In some embodiments, the
bulk-forming groups may independently comprise aryl groups
(aromatics, polycyclic aromatics, substituted aromatics,
heteroaromatics, polycyclic heteroaromatics, and substituted
heteroaromatics.
[0046] In other embodiments, the bulky groups fit preferentially
into conformationally/spatially defined areas (e.g., pockets) of
the polymer. Such areas may be referred to as preorganized for
interaction with the bulky groups. Such preorganization may result
from the polymer backbone adopting a predetermined conformation or
from groups (e.g., pendant groups) of the polymer adopting
predetermined conformation. In some embodiments, the preorganized
area of the polymer may have pi-interacting groups, pi-interacting
atoms, shape-interacting groups, H-bonding groups, etc that are
spatially disposed to preferentially interact with complementary
moieties on the bulky group. The interactions of the preorganized
area on the polymer and the bulky group may comprise any
interaction described above or any multiple combinations thereof.
In some embodiments, preorganization provides additional stability
compared to just the stabilizing interaction alone. For example,
one part of the preorganized pocket may pi-interact with a
pi-interacting moiety on the bulky group and another part of the
preorganized pocket may interact with the same or different moiety
of the bulky group with van der Waals forces.
[0047] In other embodiments, the chromophore may comprise more than
one bulky group. In some embodiments, the chromophore has at least
one bulky group on the donor and at least one bulky group on the
p-bridge or acceptor. More than one bulky group on different parts
of the chromophore may increase interactions with the polymer
backbone and make translation and depoling more difficult.
[0048] One embodiment comprises a poled nonlinear optical
chromophore and a host polymer, wherein the nonlinear optical
chromophore is substituted with two or more bulky groups and the
host polymer is configured to cooperate with the bulky groups to
impede chromophore depoling. In some embodiments, the nonlinear
optical chromophore has the structure D-.pi.-A; D is substituted
with a bulky group; and .pi. is substituted with a bulky group. In
another embodiment, the bulky groups and the polymer cooperate via
pi-interactions. I another embodiment, the bulky groups comprise
aryl groups. In some embodiments, the aryl groups independently are
an aryl hydrocarbon, an aryl polycyclic hydrocarbon, a heteroaryl,
or a polycyclic heteroaryl. In some embodiments, the host polymer
may be a polycarbonate, a poly(arylene ether), a polysulfone, a
polyimide, a polyester, a polyacrylate, or any copolymer thereof.
In some embodiments, the host polymer has a Tg greater than
150.degree. C. and may be a polysulfone; a polyester; a
polycarbonate; a polyimide; a polyimideester; a polyarylether; a
poly(methacrylic acid ester); a poly(ether ketone); a
polybenzothiazole; a polybenzoxazole; a polybenzobisthiazole; a
polybenzobisoxazole; a poly(aryl oxide); a polyetherimide; a
polyfluorene; a polyarylenevinylene; a polyquinoline, a
polyvinylcarbazole; or any copolymer thereof.
[0049] Another embodiment is an electro-optic device comprising any
of the polymers described herein, wherein the V.pi. of the device
is operational after 2000 hours at 85.degree. C. In some
embodiments, the electro-optic device has a V.sub..pi. that does
not increase more than 5% after 2000 hours at 85.degree. C. In some
embodiments, the electro-optic device has a V.sub..pi. that does
not increase more than 10% after 2000 hours at 85.degree. C. In
some embodiments, the electro-optic device has a V.sub..pi. that
does not increase more than 15% after 2000 hours at 85.degree. C.
In some embodiments, the electro-optic device has a V.sub..pi. that
does not increase more than 20% after 2000 hours at 85.degree.
C.
[0050] In some embodiments, an electro-optic polymer comprises a
nonlinear optical chromophore and a host polymer, wherein: the
nonlinear optical chromophore has a bulky substituent comprising at
least one aryl group and the host polymer has an aryl group
selected to interact with the aryl group of the substituent. In
some embodiments, wherein the substituent comprises 2 or 3 aryl
groups. In some embodiments, the chromophore has the structure
D-.pi.-A and the triaryl group has the structure
##STR00016##
wherein: D is a donor; .pi. is a .pi.-bridge; A is an acceptor; X
is a substituent center; Ar.sup.1, Ar.sup.2, and Ar.sup.3 are the
aryl groups; and L is a covalent linker attached to D, .pi. or
A.
[0051] In another embodiment, an electro-optic polymer includes a
nonlinear optical chromophore having the structure D-.pi.-A,
wherein D is a donor, .pi. is a .pi.-bridge, A is an acceptor, and
at least one of D, .pi., or A is covalently attached to a bulky
group comprising at least one aryl group, and wherein the
electro-optic polymer has greater temporal stability than when an
alkyl group is substituted for the aryl group. In some embodiments,
the bulky group comprises at least two aryl groups, and the
electro-optic polymer has greater temporal stability than when
alkyl groups are substituted for the aryl groups. In another
embodiment, the bulky group comprises at least three aryl groups,
and the electro-optic polymer has greater temporal stability than
when alkyl groups are substituted for the aryl groups.
[0052] In another embodiment, an electro-optic polymer comprises a
nonlinear optical chromophore and a host polymer, wherein the
nonlinear optical chromophore has a substituent group comprising at
least two aryl groups, the host polymer comprises a subunit
comprising at least two aryl groups, and the aryl groups of the
nonlinear optical chromophore align preferentially with the aryl
groups of the subunit (e.g., the alignment shown in FIG. 14). In
some embodiments, the host polymer is a polysulfone; a polyester; a
polycarbonate; a polyimide; a polyimideester; a polyarylether; a
poly(methacrylic acid ester); a poly(ether ketone); a
polybenzothiazole; a polybenzoxazole; a polybenzobisthiazole; a
polybenzobisoxazole; a poly(aryl oxide); a polyetherimide; a
polyfluorene; a polyarylenevinylene; a polyquinoline, a
polyvinylcarbazole; or any copolymer thereof.
[0053] Compatibility and stability of composites comprising
chromophores having bulky groups with various host polymers were
studied, including the EO properties. Low optical loss is achieved
due to good compatibility, which also is proven by a clean, single
Tg transition. EO coefficients with various host polymers are
characterized and their temporal stability is monitored at
different temperatures. Meanwhile, modulators were fabricated out
of those EO composites and their stability is further
confirmed.
[0054] Some embodiments have a chromophore structure that comprises
bulky groups. Such chromophores show good compatibility with host
polymers and lead to high glass transition temperature. Examples of
two chromophores are shown in FIGS. 1-4. Guest-host systems were
studied using these chromophores with various host polymers with
different glass transition temperature. Host polymers such as 28,
29, and 30 in FIG. 6 belong to polycarbonate family with low to
high Tg. In some embodiments, high Tg of the host polymers will
lead to higher Tg of the EO composites with the same
chromophore.
[0055] According to embodiments, EO composites having high Tg
(>120.degree. C.) may be fabricated by using a host polymer with
a glass transition temperature >120.degree. C. In other
embodiments, EO composites having high Tg (>120.degree. C.) may
be fabricated by using a host polymer with a glass transition
temperature >120.degree. C. and a chromophore with a melting
point or Tg>120.degree. C. For example, an EO composite
including chromophore 23b (FIG. 4) in 28 (Tg=286.degree. C.) to
have a composite Tg of 167.degree. C. Similarly, results showed an
EO composite including 23b chromophore in host polymer 29
(Tg=165.degree. C.) to have a composite Tg of 193.degree. C. Both
systems showed improved stability for long term applications having
a maximum service temperature of 85.degree. C. Chromophore 23a has
similar improved stability (Tables 1 and 2 below). In another
embodiment, an electro-optic composite comprises greater than 35%
loading by weight of a chromophore in a host polymer, wherein the
Tg of the composite is higher than the melting point, or Tg, of the
chromophore itself. In some embodiments, the chromophore loading by
weight is at least 45% and the Tg of the composite is greater than
150.degree. C. In another embodiment, the host polymer may be a
semi-crystalline polymer with a low Tg that, when mixed with a
chromophore, forms an amorphous composite with high Tg. In some
embodiments, noncovalent interactions between bulky groups on the
chromophore and moieties of the semi-crystalline host polymer
increase the Tg of the amorphous composite.
[0056] According to embodiments, other host polymers with Tg higher
than 150.degree. C. may be used in combination with chromophores
having bulky groups to produce composite EO materials having high
Tg, and therefore high temperature stability over short and/or long
terms. Illustrative high Tg host polymers may be formed from the
following polymeric systems and/or their combinations:
polysulfones; polyesters; polycarbonates; polyimides;
polyimideesters; polyarylethers; poly(methacrylic acid esters);
poly(ether ketones); polybenzothiazoles; polybenzoxazoles;
polybenzobisthiazoles; polybenzobisoxazoles; poly(aryl oxide)s;
polyetherimides; polyfluorenes; polyarylenevinylenes;
polyquinolines, polyvinylcarbazole; and their copolymers.
[0057] According to an embodiment, an electro-optic polymer
includes a nonlinear optical chromophore having the structure
D-.pi.-A, wherein D is a donor, .pi. is a .pi.-bridge, A is an
acceptor, and at least one of D, .pi., or A is covalently attached
to a substituent group including a substituent center X that is
directly bonded to an aryl group, and wherein the electro-optic
polymer has greater temporal stability than when an alkyl group is
substituted for the aryl group. The electro-optic polymer may be a
side-chain, crosslinked, dendrimeric, or composite material.
According to an embodiment, the substituent center X is bonded to
at least three aryl groups, and the electro-optic polymer has
greater temporal stability than when alkyl groups independently are
substituted for the aryl groups. According to an embodiment, the
electro-optic composite has greater than 80% temporal stability at
85.degree. C. after 100 hours.
[0058] Other embodiments include various methods for making
electro-optic composites, and devices therefrom, where the
electro-optic composite includes a chromophore as described above.
According to an embodiment, a method includes: a) providing a
polymer including a nonlinear optical chromophore having the
structure D-.pi.-A, wherein D is a donor, .pi. is a .pi.-bridge, A
is an acceptor, and at least one of D, .pi., or A is covalently
attached to a substituent group including a substituent center that
is directly bonded to an aryl group; and b) poling the polymer to
form and electro-optic polymer, wherein the electro-optic polymer
has greater temporal stability than when an alkyl group is
substituted for the aryl group.
[0059] Typically, an aryl group is sterically larger than an alkyl
group. Typically, the polymer may be provided as a film by, for
example, spin deposition, dip coating, or screen printing. The thin
film may also be modified into device structures by, for example,
dry etching, laser ablation, and photochemical bleaching.
Alternatively, the polymer may be provided by, for example, molding
or hot embossing a polymer melt. The poling may include, for
example, contact or corona poling. In another method embodiment,
the substituent center is bonded to or substituted with at least
three aryl groups, and the electro-optic polymer has greater
temporal stability than when alkyl groups independently are
substituted for the aryl groups.
[0060] In some embodiments, the polymer is a composite. In some
method embodiments, the aryl group is sterically larger than the
alkyl group. In another method embodiment, the polymer has a
T.sub.g; the T.sub.g of the polymer is within approximately
5.degree. C. compared to when an alkyl group is substituted for the
aryl group, and the temporal stability of the polymer is greater
compared to when an alkyl group is substituted for the aryl
group.
[0061] Another embodiment is an electro-optic polymer comprising a
nonlinear optical chromophore comprising the donor (24, FIG.
5):
##STR00017##
wherein R.sup.1 independently comprises and alkyl, heteroalkyl,
aryl, or heteroaryl group; R.sup.2 independently at each occurrence
comprises an H, alkyl group, heteroalkyl group, aryl group, or
heteroaryl group; R.sup.3 independently at each occurrence
comprises a halogen, an alkyl group, and heteroalkyl group, an aryl
group, or a heteroaryl group; and n is 0-3. Chromophores according
to this embodiment may be prepared, for example, according to the
general scheme 25 to 27 shown in FIG. 5. Chromophore according to
this embodiment have good nonlinearity due to the strong donating
group and can be derivatized with a number of functional groups at
the --R.sup.1 position. In one embodiment, --R.sup.1 comprises a
bulky group that interactions with the polymer host and the
.pi.-bridge includes a bulky group that interacts with the polymer
host.
[0062] Other embodiments are electro-optic devices including the
nonlinear optical chromophores, electro-optic composites, and
electro-optic polymers as described above. The devices may include
planar waveguides, free standing thin films, single and multi-mode
optical waveguides, and other polymers that are passive (e.g., clad
polymers such as acrylates). The devices may also have polymers
having combinations of any one of the chromophores and/or with
other nonlinear optical chromophores. Additionally, a particular
device may have two or more different composites and/or polymers
including any one of the chromophores above (e.g., a electro-optic
waveguide core polymer having one chromophore with a relatively
high refractive index and a clad polymer having either the same
chromophore in less concentration or a different chromophore so
that the refractive index of the clad is lower). In some
embodiments, the electro-optic device includes a Mach-Zehnder
interferometer, a Michelson interferometer, a micro-ring resonator,
or a directional coupler.
EXAMPLES
[0063] The following synthetic example refers to FIG. 2.
[0064] Compound 2: To compound 1 (10.00 grams) in dioxane (50 ml)
in ice bath was added t-BuOK (1M, 55 ml) and Methyl thioglycolate
(5.279 grams). The reactants were heated to 80.degree. C. for 2
hours and then to 120.degree. C. for 30 min. Then, most of dioxane
was distilled off. 1-Bromobutane (20 ml) and DMSO (80 ml) was
added. The reaction was heated to 150.degree. C. for 2 hours. After
the reaction was cooled to room temperature, acetic acid in ice
water was used to acidify the reaction. The product was extracted
with dichloromethane. The dichloromethane layer was separated,
dried over MgSO.sub.4, filtered, and evaporated to give crude
product, which was purified by column chromatography on silica gel
to give 10.7 grams of liquid product 2.
[0065] Compound 3: Compound 2 (7.72 grams) was dissolved in dry
ether under nitrogen. The flask was cooled in dry ice-acetone
cooling bath. LiAlH.sub.4 (1.08 grams) was added. The cooling bath
was removed so that the reaction temperature was brought to room
temperature, at which the reaction was kept for 6 hours. The flask
was cooled in ice bath. Methanol was added drop-wise to quench the
reaction. Brine was added. The organic layer was separated. The
aqueous layer was extracted with ether. The combined organic layers
were dried over MgSO.sub.4, filtered through silica gel packed in
funnel. After evaporation, compound 3 was obtained in 4.65
grams.
[0066] Compound 4: Compound 3 (4.65 grams) was dissolved in
chloroform (100 ml). The flask was cooled in ice bath while
triphenylphosphine hydrobromide was added. The reaction was stirred
at 0.degree. C. for 30 min, then room temperature for 14 hours,
then refluxed for 3 hours. The reaction mixture was precipitated in
ether two times to give 8.93 g of product 4.
[0067] Compound 6: Compound 4 (6.71 grams) and compound 5 (5.22
grams) were mixed in dry THF (100 ml) under nitrogen and cooled in
an ice bath. t-BuOK (1M in THF, 15 ml) was dropped into the mixture
via needle. The reaction was stirred at room temperature overnight
and quenched with water. The mixture was neutralized with acetic
acid. The product was extracted with methylene chloride and
purified by flash column using a hexane-methylene chloride mixture
to give 3.10 grams of compound 6.
[0068] Compound 7: Compound 6 (1.68 grams) was dissolved in dry THF
(35 ml) under nitrogen. n-BuLi (2.5M, 1.15 ml) was dropped in via
needle at -78.degree. C. The reaction was kept at -30.degree. C.
for 70 min. Then, DMF (0.30 ml) was added via needle at -78.degree.
C. After 45 min, the reaction was terminated with ice water. The
product was extracted with methylene chloride, dried over
MgSO.sub.4, evaporated, and purified by flash column to give
compound 7 (1.32 grams).
[0069] Compound 9: Compounds 7 (1.264 grams) and 8 (0.767 grams)
(see U.S. Pat. No. 7,078,542 and references therein for preparation
of acceptor compounds of this type) were mixed in 10 ml ethanol and
5 ml dry THF under nitrogen. The mixture was heated to 45.degree.
C. The reaction was monitored by TLC. When compound 7 disappeared
from reaction mixture, the solvent was evaporated on rotary
evaporator. The residue was purified by flash column and
precipitation of methylene chloride solution in methanol to give
1.03 grams of compound 9 as black powder. U.S. Pat. No. 7,078,542
is incorporated by reference herein.
[0070] Compound 10: A total of 5.69 grams of 9 was dissolved in THF
(100 ml) under nitrogen. 5 ml of 2N HCl was added. The reaction was
stirred at room temperature and monitored by TLC. When the compound
9 disappeared from the reaction mixture, methylene chloride (200
ml) and brine (100 ml) was added. The mixture was neutralized with
saturated sodium bicarbonate solution. The organic layer was
separated, dried over MgSO.sub.4, evaporated, and purified by flash
column successively to give 5.69 g of compound 10.
[0071] Compound 11: Compound 10 (5.68 grams) was mixed with
methylene chloride (50 ml). The flask was cooled in ice bath.
triphenylchlorosilane (6.10 grams) and imadazole (1.40 grams) was
added successively. The reaction was stirred and monitored by TLC.
After about 30 minutes, compound 10 disappeared from the reaction
mixture. The salt was filtered out. The product was purified by
flash column and precipitation of methylene chloride solution in
methanol to give 4.10 grams of compound 11.
[0072] Other chromophores were prepared using similar reactions and
other starting materials. For example, when X.dbd.C, trityl
chloride (Ph.sub.3C--Cl) may be used in a reaction analogous to
that for compound 11.
[0073] 30 wt % of compound 11 in APC (APC=[biphenyl A
carbonate-co-4,4'-(3,3,5-trimethylcyclo-hexylidene)diphenol
carbonate] (28), see U.S. Pat. No. 6,750,603) showed very good EO
activity of r.sub.33=81 pm/V and very good temporal stability of
92% retention after 20 hours at 85.degree. C. Temporal stability
tests on a Mach-Zehnder modulator showed better than 95% retention
of V.sub..pi. after 100 hours at 85.degree. C.
[0074] The following synthetic example refers to FIG. 3.
[0075] Compound 13: Compound 12 was dissolved in 70 mL THF while 1N
HCl solution (20 mL) was added. It was stirred at room temperature
for 2 hours. The mixture was extracted with CH.sub.2Cl.sub.2,
washed with NaHCO.sub.3 solution and water, and dried over
MgSO.sub.4. After evaporating solvent under reduced pressure, it
was purified by column chromatography with CH.sub.2Cl.sub.2/MeOH
(5/0.5) as eluting solvents. At total of 1.65 g of compound 13 was
obtained in 67% yield.
[0076] Compound 14: Compound 13 (0.8 g, 1.07 mmol) and
triphenylsilyl chloride (0.945 g, 3.2 mmol) were dissolved in 20 mL
of CH.sub.2Cl.sub.2. After immidazole (0.22 g, 3.2 mmol) was added,
the mixture was stirred at room temperature for 1.5 hours. It was
then filtered and the solvent was removed under reduced pressure.
It was purified by column chromatography to give compound 14 as a
solid.
[0077] A 50% compound 14 in amorphous polycarbonate (APC) composite
had an r.sub.33 of 90 pm/V, an optical loss of 0.881 dB/cm, a
T.sub.g of 140.degree. C., an index of refraction of 1.6711 at 1.55
microns, and a temporal stability in Mach-Zehnder modulators
similar to 30% compound 11 in APC as described above. A 24%
compound 12 in APC composite, in which the aryl groups are
substituted (replaced) with alkyl groups, had an r.sub.33 of 50
pm/V, an optical loss of 1.44 dB/cm, T.sub.g of 140.degree. C., an
index of refraction of 1.6038 at 1.55, and a much lower temporal
stability.
[0078] Compound 16: To a 3-L three necked flask with a stir bar was
charged 125 grams of trimethyl-tetrahydroquinoline (15), and 102
grams of anhydrous potassium carbonate (K.sub.2CO.sub.3). Set the
flask with a condenser, and an additional funnel containing 173.3
grams of p-bromobenzyl bromide in 500 ml dry DMF. The air in flask
was flash with nitrogen. 700 ml of dry DMF was added to flask. The
flask was cooled in ice-water bath. p-bromobenzyl bromide was
dropped into the flask from the additional funnel attached to flask
while stirring is on. After completion of the addition, the
reaction was kept at room temperature for 3 hours. The reaction was
heated in 55-60.degree. C. for 14 hours (overnight). The content
was allowed to cool down to room temperature, 1 liter of hexanes
was added to flask. After stirring for 10 min, the solid was
filtered off. The solution was evaporated on rotary evaporator to
dryness. The mixture was dissolved in ethyl acetate (1 L), washed
with brine two times, dried over MgSO4, filtered, and evaporated.
The product was purified by chromatography on silica gel packed in
chromatographic column with hexanes/DCM as mobile phase.
[0079] Compound 17: A 2-l flask equipped with additional funnel and
stir bar was charged with 66.66 grams of compound 16 from previous
step. The flask was degassed and filled with dry nitrogen.
Anhydrous THF (800 ml) was added into flask. The flask was cooled
in dry ice-acetone bath. n-BuLi (83 ml) was added from the
additional funnel slowly. The reaction was kept at -60.degree. C.
for 2.5 hours. In another 3-liter 3-necked flask with 55.7 grams of
triphenylchlorosilane and 200 ml anhydrous THF was prepared and
cooed in dry ice-acetone bath. Under stirring, the lithiated
solution from the first flask was added into the second flask with
stirring during 1 hour. The reaction was stirred overnight and was
quenched with acetic acid aqueous solution (0.19 mol acetic acid in
300 ml water) and some brine solution. The organic layer was
separated and washed with brine once, dried over MgSO4, filtered,
and evaporated to dryness. The product was purified by silica gel
columns using hexanes/DCM as mobile phase.
[0080] Compound 18: 147 grams of compound 17 was dissolved in 1000
ml of dry DMF in a 3-L flask under nitrogen. NBS (51.23 grams)
together with 500 ml of DMF was charged in an additional funnel.
The flask was cooled in ice bath and wrapped with aluminum foil to
keep light from the reaction. Te NBS solution was dropped into
LM-667 drop wise. The reaction was stirred at room temperature
overnight. DMF was evaporated. The mixture was stirred in
Hexanes/ethyl acetate (3:1). The precipitation was filtered off.
The solution was evaporated. The residual mixture was stirred in
methanol. The solid was collected by filtering. Repeat the methanol
wash one more time. The solid was purified by silica gel column
chromatography (Hexane/DCM=2:1) and dried under vacuum. Yield of
compound 18 is 95%.
[0081] Compound 19: 150 grams of compound 18 was charged into a 3-l
3-necked flask with a stir bar and additional funnel. The flask was
flashed with nitrogen 4 times. 1200 ml of anhydrous THF was added
via cannulation. The flask was cooled in dry ice-acetone bath. 286
ml of t-BuLi (1.7M) was added drop wise from the additional funnel.
After completion of dropping, the funnel was washed with 25 ml of
THF. Then, DMF (anhydrous, 35.81 g) in THF (200 ml) was added drop
wise from the funnel. The cooling bath was removed to allow the
reaction temperature to reach 0.degree. C. in ice bath-water bath.
The reaction was quenched with acetic acid aqueous solution (5:1)
until PH value is about 7. Some brine and 500 ml of hexanes were
poured into the mixture. The organic layer was separated, dried
over MgSO4, filtered, and evaporated. The product was purified by
silica gel column chromatography using hexane/DCM (3:1 to 1:1) and
methanol wash. Yield of the corresponding aldehyde was 85%. The
aldehyde (27.8 grams) was charged into a 1 liter flask with a stir
bar. Dry THF (500 ml) was added. The mixture was stirred with some
heat to form homogenous solution. The flask was cooled in ice bath.
1.86 grams of sodium borohydride (NaBH.sub.4) was added. The flask
was flashed with nitrogen. 25 ml of ethanol in 50 ml THF was added
from an additional funnel during two hours. The reaction was kept
stirring at room temperature for 18 hours. The reaction is reached
full conversion when the solution is near clear. When the reaction
is finished, brine (50 ml) was added to the reaction and kept
stirring for 45 min under high speed. The organic layer was
separated, dried over MgSO4, evaporate. The product was purified
with flash column chromatography using hexanes/ethyl acetate. The
yield of compound 19 is 95%, which was used directly for next step
without further characterization.
[0082] Compound 20: A total of 25 grams of compound 19 was
dissolved in chloroform (200 ml) in a 1-L flask. The flask was
cooled in ice bath. Ph.sub.3PHBr (15.2 g) dissolved in chloroform
(200 ml) was dropped into LM-671 during 1 hour or so. After
stirring at room temperature for 3 hours, the reaction was
reconfigured with Deans-Stark reflux trap to separate water by
azeotropic removing chloroform-water distillate for 6 hours. The
reaction was cooled down, evaporated to about 100 ml solution. This
thick solution was precipitated in dry ethyl ether while stirring
is on. The product collected by filtering was dissolved in DCM and
precipitated again in dry ether. The greenish product was dried
over vacuum for a day. Yield of compound 20 is 85%. Proton NMR was
collected for characterize the compound structure.
[0083] Compound 21: A Total of 0.1 mol of compound 22 in 200 ml dry
dichloromethane in a flask was cooled in ice water. Imidazole (0.15
mol) was added. The flask was flashed with nitrogen.
t-butyldimethylchlorosilane was added dropwise using syringe. The
reaction was stirred for 1 hour. The precipitation was filtered
out. The solution was washed with brine, dried over magnesium
sulfate and evaporated. The product 10 was purified by flash
chromatography over silica gel. The yield of the corresponding
TBDMS ether is 85%. The TBDMS ether (8.37 g) was charged in a flask
with a stir bar. The flask was degassed and refilled with nitrogen.
n-Buli in hexane was added dropwise from a needle. The reaction was
kept between -10.degree. C. and -20.degree. C. for 2 hours. Then
DMF was added at -78.degree. C. The reaction was quenched by acetic
acid in water. The organic layer was separated, washed with brine,
dried over magnesium, and evaporated. The product mixture of two
regioisomers was purified by chromatographic column. The yield of
compound 21 is 60%.
[0084] Compound 23: To a flask, compound 20 (27.01 g) was charged
and degassed. Dry THF was added to the flask. n-BuLi in hexane was
added dropwise at -20.degree. C. The reactants were stirred in ice
bath for 1 hour. To a second flask, compound 21 (9.511 g) was
dissolved in dry THF. The mixture in flask one was added to the
second flask under cooling and stirring. The mixture was stir 16
hour at room temperature. The reaction was stop by adding water and
some brine. The organic layer was separated, dried over magnesium
sulfate, filtered, and evaporated to dryness. The mixture was
purified by flash chromatography to give the corresponding Wittig
coupling product in a yield of 66%. The coupling product was
dissolved in dry THF in a flask with a stir bar. n-Buli in hexane
was added using syringe. The reaction was kept at -20.degree. C.
for 2 hours. DMF in THF was added. The reaction was quenched by
brine and acetic acid. The organic layer was separated, washed with
water, dried over magnesium sulfate, filter using Buchner funnel,
The mixture was purified by silica gel column chromatography using
dichloromethane-hexane mixture as mobile phase to give the
corresponding aldehyde. The aldehyde was dissolved in acetone in a
flask under nitrogen. 3N HCl aqueous solution was added. The
mixture was stirred at room temperature and monitored by TLC. When
the reaction reached the end. The mixture was neutralized with
saturated sodium bicarbonate solution. Acetone was evaporated. The
product was extracted with THF and purified further by flash column
chromatography using THF-DCM as mobile phase to give the
corresponding deprotected alcohol. (23a): The deprotected alcohol
in a flask was dissolved in dry dichloromethane. Trityl chloride,
diisopropylethylamine, 4-dimethylaminopyridine was added. The
reaction was stirred for 16 hours. The precipitation was filtered.
The solution was washed with water, dried with magnesium sulfate,
filtered, and evaporated. The product was purified with flash
chromatography to give the corresponding trityl ether. The trityl
ether and
2-dicyanomethylene-3-cyano-4-methyl-5-trifluoromethyl-5-(4'-phenyl)phenyl-
-2,5-dihydrofuran (8, FIG. 2) were mixed in ethanol in a flask. The
reaction was heated at 60.degree. C. for 6 hours. The content was
cooled to room temperature. The mixture was filtered. The filtrate
was purified by column chromatography combined with methanol or
ethanol washed to give chromophore compound 23a; (23b) The
deprotected alcohol and
2-dicyanomethylene-3-cyano-4-methyl-5-trifluoromethyl-5-(4'-phenyl)phenyl-
-2,5-dihydrofuran (8, FIG. 2) were stirred in ethanol in a flask
under nitrogen at 60.degree. C. The reaction was monitored by TLC.
After 6 hours, the content was cooled to room temperature. The dark
solid was collected by filtration on Buchner funnel. The material
was further purified by silica gel column chromatography and
re-crystallization to give a black powder of the
chromophore-alcohol with a yield of 60%. The chromophore-alcohol
was dissolved in dry dichloromethane in a flask with a stir bar.
Imidazole and triphenylchlorosilane was added. The reaction was
monitored by thin layer chromatography. After 30 min. the
precipitation was filtered. The solution was washed with brine,
dried over magnesium sulfate, filtered, and evaporated. The
compound was further purified by flash column chromatography,
crystallization and wash with hexanes. Yield of compound 23b is
70%.
[0085] Guest-host EO polymers were prepared with chromophores 23a
and 23b with host polymers 28-30 (FIG. 6). The properties of the EO
polymer are shown in Table 1 and Table 2. The number in parentheses
behind the material reference numbers is the loading % by weight of
the chromophore. High Tg of host polymers will lead to higher Tg of
the EO composites with the same chromophore. In Table 1 and Table
2, composites with 29 show higher Tg than 28 composites with the
same loading. The composites have similar optical loss and EO
coefficient.
TABLE-US-00001 TABLE 1 Major EO properties of chromophore 23a.
28-23a 28-23a 29-23a 30-23a Property (50%) (55%) (50%) (55%)
r.sub.33 @ 1.3 .mu.m 92 95 90 High leak (pm/V) (corrected) through
current Optical Loss 1.1-1.2 1.2-1.3 1.3 1.4 @ 1.55 .mu.m (dB/cm)
Chromophore 159 159 159 159 T.sub.g (.degree. C.) EO Polymer 175
174 199 >202 T.sub.g (.degree. C.) Refractive Index 1.7141
1.7300 1.7116 1.6793 @ 1.5 .mu.m (unpoled) (TM) (poled)
TABLE-US-00002 TABLE 2 Major EO properties of chromophore 23b
28-23b 29-23b 29-23b 30-23b Property (50%) (50%) (55%) (55%)
r.sub.33 @ 1.3 .mu.m 87-107 -- 80-95 -- (pm/V) (corrected) Optical
Loss 1.2-1.3 1.3 1.3 1.3 @ 1.55 .mu.m (dB/cm) Chromophore 157 157
157 157 T.sub.g (.degree. C.) EO Polymer 167 199 193 -- T.sub.g
(.degree. C.) Refractive Index 1.7339 1.6625 1.7320 1.6926 @ 1.5
.mu.m (unpoled) (unpoled) (TM) (poled)
[0086] To study the long-term stability of EO polymers, accelerated
aging tests have been performed. In these tests the EO polymer
films were poled using Indium Tin Oxide (ITO) as substrate. The
poled samples were then sealed in a vacuum environment to avoid the
possible oxygen related degradation and placed into ovens set at
various elevated temperatures. The decay of the EO coefficient
r.sub.33 was monitored as a function of time up to 2000 hours. EO
polymer composite 28-23a (50%) (Tg 175.degree. C.) was studied at
85, 100, and 110.degree. C. (FIG. 7A). At 85.degree. C., r.sub.33
remained at 94% of the initial r.sub.33 after 2000 hours of
testing. We also studied 28-23b (55%) and 29-23b (55%) at
85.degree. C., 100.degree. C., and 110.degree. C. (FIGS. 7B, 7C,
7D, respectively). The Tg of 28 and 29 is respectively 167.degree.
C. and 193.degree. C. The graphs FIG. 7B-D show normalized tested
r.sub.33 values at aging times up to 1800 hours at each
temperature. In FIG. 7b, a 29 composition showed stability
marginally better than the 28 composition. The difference in
stability is relatively small because of the large temperature
difference between their respective Tg and the 85.degree. C. test
conditions. At 100.degree. C. (FIG. 7C), the 29 system had 2.5%
better stability than the 28 system. At 110.degree. C. (FIG. 7D),
the 29 system showed 9% better stability than the 28 system. The 29
system was found to have higher temporal stability than the 28
system at each temperature, with the difference in stability being
more marked at higher application temperatures. The effect of the
higher host polymer Tg was to significantly enhance the composite
Tg, and hence to enhance the stability of the measured EO
coefficient.
[0087] Among different models proposed in the literature we
discovered that one, incorporated by reference herein, published by
Lindsay et al., Polymer 48 (2007), 6605-6616 showed good
consistency between the experimental data and model prediction and
is most relevant to our work. We applied the isothermal aging model
Jonscher equation
V.sub..pi.(t)/V.sub..pi.(0)=1+(t/.tau.).sup.j
together with Lindsay's hyperbolic tangent approach:
ln(.tau./.tau..sub.P)=E.sub.R(1+tan
h[(T.sub.c-T)/D])/2RT+E.sub.P/RT
to model the temperature dependence of the relaxation and to derive
the activation energy of our poled EO polymer systems. In the
model, E.sub.R and E.sub.P are the activation energies of the rigid
glassy state and the pliable state, respectively. T.sub.c and D are
the central temperature and the width of the transition zone.
[0088] The experimental data and the curve fitting results using
the Jonscher equation for 28-23a (50%) at three different
temperatures 85, 100 and 110.degree. C. are shown in FIG. 7E. It
can be seen that there is a good consistency between our
experimental data and the modeling results. Based on the Jonscher
equation fitting, we obtained the fitting parameters .tau. (time
constant) and j (the exponent) for all five temperatures tested. We
then used these .tau. and j to further extrapolate the r.sub.33
decay (or V.sub..pi. increase) of our EO materials at 25 years.
FIG. 7B shows the extrapolation of the normalized V.sub..pi.
increase in 25 years for 28-23a (50%) at 85, 100 and 110.degree. C.
Under 85.degree. C. operation, the model predicts a V.sub..pi.
increase of only 1.14 times. This is a significant improvement in
the long-term stability compared to other existing EO polymer
systems such as CLD-PI (80.degree. C., FIG. 7B) reported in
Lindsay.
[0089] We also show the curve fitting results using the hyperbolic
tangent model (FIG. 8):
ln(.tau./.tau..sub.P)=E.sub.R(1+tan
h[(T.sub.c-T)/D])/2RT+E.sub.P/RT
proposed in Lindsay for EO polymers 28-14 (50%), 28-23a (50%),
28-23b (55%), and 29-23b (55%). For comparison purposes, we also
re-plotted the curve for CLD-PI (CLD-APEC). The activation energies
of 28-14 (50%) (1.09 eV) and 28-23b (1.14 eV) systems are in a
similar range. Additionally, switching from 28-14 (50%)
(Tg=140.degree. C.) to 28-23a (Tg=175.degree. C., FIG. 8A) or
28-23b (Tg=167.degree. C., FIG. 8B), the transition zone where the
material stability drastically degrades is pushed significantly
toward higher temperature range (in this case about 20.degree. C.
higher). Similar behavior is seen with 29-23b (Tg=193.degree. C.
FIG. 8A and FIG. 8B).
[0090] The Jonscher equation was also used to compare 28-23b (55%)
with 29-23b (55%) at 85.degree. C. and 110.degree. C. (FIG. 9). At
85.degree. C., there was no significant difference in long term
stability. At 110.degree. C., 29-23b (55%) exhibited a 33% increase
and 28-23b (55%) showed an 81% increase. This indicates that higher
Tg polymer systems (e.g., 29) show advantages at higher operation
temperature in long term performance.
[0091] Mach-Zehnder EO polymer modulators with 23a and 23b with
inverted-rib waveguides were fabricated on 3 inch wafers. The
device process flow is illustrated in FIG. 10. Bottom electrodes
were sputtered and patterned, then the wafer was treated with an
adhesion promoter having thiol and polar groups, then a layer of
bottom clad (LP202C (a thermally curable, crosslinked sol-gel
material), or UV15LV) was spun and cured. Inverted-rib waveguides
were then fabricated on the bottom clad. After a plasma surface
treatment of the bottom clad and the rib waveguides, the core layer
of composites comprised of host polymer and chromophore 23a or 23b
was deposited and thermally cured. The top clad LP33ND (a thermally
curable, crosslinked sol-gel material) was spun and thermal cured
after a surface treatment of the core layer. After the entire
optical material stack of the device was built, the poling
electrodes were deposited and patterned, followed by a poling
process that was performed at a temperature range from 164.degree.
C. to 220.degree. C. with a bias voltage range from 750V to 950V to
align the chromophores. The choice of poling temperature and
voltage depends on the core materials. The poling electrodes were
also designed to serve as working electrodes with an active length
of 2.1 cm. The devices were diced into individual chips for
testing. The electrode configuration is shown in FIG. 11 and the
cross sectional view of one of the polymer modulators is shown in
FIG. 12.
[0092] Optical insertion loss, half-wave voltage (V.sub..pi.), and
extinction ratio were measured. Device V.sub..pi. and insertion
loss are tabulated in Table 3. There is no significant difference
between 23a and 23b with 28 as host polymer. Their insertion losses
are also similar. When using 23b with 29 as host polymer, the
V.sub..pi. is higher.
TABLE-US-00003 TABLE 3 V.sub..pi. and Insertion Loss of EO polymer
modulators Insertion Loss EO Polymer Chip ID V.pi. (V) (-dB/cm)
28-23a (50%) V25-25-A 1.28 9.1 28-23a (55%) V25-8-C 1.09 10.8
28-23b (55%) V25-43-C 1.16 9.8 29-23b (55%) V26-14-B 1.42 8.3
[0093] Mach-Zehnder devices using 28-23b (55%) were studied at
85.degree. C. for up to 1300-3000 hr (FIG. 13a). The normalized
V.sub..pi. of the 28-23b (55%) device was found to increase to
about 1.02-1.04 times the baseline (initial) V.pi., which
corresponds to a 2-4% decrease of r.sub.33, which corresponds well
to thin film r.sub.33 tests. Using a Jonscher model to project
25-year performance (FIG. 13b), it is expected that devices made
with 28-23b (55%) materials will exhibit an 11% V, increase over 25
years.
[0094] Device V.sub..pi. stability was also studied for the higher
Tg core 29-23b (55%). After 265 hr at 100 and 110.degree. C.,
respectively, V.pi. was found to increase by 1.04 and 1.07 over the
initial V.pi.. We observed better stability of devices using a
higher Tg core including the higher Tg host polymer 29. We further
tested 29-23b (55%) up to 150.degree. C. and 170.degree. C. for 30
minutes, and found V.pi. increases from the initial V.pi. of 1.12
and 1.49 times, respectively. This indicates that short time
exposures to high elevated temperatures does not ruin the device
performance, thus making devices fabricated from this material more
compatible with elevated temperature processing and/or more immune
to failure resultant from short term over-temperature
conditions.
[0095] While various aspects and embodiments have been disclosed
herein, other aspects and embodiments are contemplated. The various
aspects and embodiments disclosed herein are for purposes of
illustration and are not intended to be limiting, with the true
scope and spirit being indicated by the following claims.
* * * * *