Thermally stable nonlinear optical polymers based on polyimides substituted with chromophores containing julolidine moiety

Article abstract of DOI:10.1080/15421400802329590

We designed and synthesized a NLO chromophore adopting the concept of shape modification as well as possessing high thermal stability. The chromophore was featured by a phenylene ring as a conjugation bridge, a bulky alkyl chain attached on the side of the conjugation bridge, and julolidine moiety as an electron donor. The NLO chromophore was attached to the polyimide as a side chain, resulting in thermally durable NLO polymers. On set decomposition temperature of the NLO chromophore was measured 330°C in TGA analysis. The NLO polymer exhibited high glass transition temperature of 150°C and was thermally stable up to 250°C. The polymer was quite soluble in common solvents and produced an optical quality film by spin-coating. The electro-optic coefficient of the film was measured using 1.55 μm laser source, giving as high as 30 pm/V at the poling condition of 150°C and 1 MV/cm.

Full text of DOI:10.1080/15421400802329590

This article was downloaded by: [Florida Atlantic University]
On: 08 October 2013, At: 23:40
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954
Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH,
UK
Molecular Crystals and Liquid
Crystals
Publication details, including instructions for
authors and subscription information:
http://www.tandfonline.com/loi/gmcl20
Thermally Stable Nonlinear
Optical Polymers Based on
Polyimides Substituted with
Chromophores Containing
Julolidine Moiety
Hyun Kyung Ju a b , Jong Sun Lim a , Changjin Lee a ,
Dong Hoon Choi b & Dong Wook Kim a
a Advanced Materials Division, Korea Research
Institute of Chemical Technology , Daejeon, Korea
b Department of Chemistry , Korea University ,
Seoul, Korea
Published online: 22 Sep 2010.
To cite this article: Hyun Kyung Ju , Jong Sun Lim , Changjin Lee , Dong Hoon Choi
& Dong Wook Kim (2008) Thermally Stable Nonlinear Optical Polymers Based on
Polyimides Substituted with Chromophores Containing Julolidine Moiety, Molecular
Crystals and Liquid Crystals, 491:1, 152-163, DOI: 10.1080/15421400802329590
To link to this article: http://dx.doi.org/10.1080/15421400802329590
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the
information (the “Content”) contained in the publications on our platform.
However, Taylor & Francis, our agents, and our licensors make no
representations or warranties whatsoever as to the accuracy, completeness,
or suitability for any purpose of the Content. Any opinions and views
expressed in this publication are the opinions and views of the authors, and
are not the views of or endorsed by Taylor & Francis. The accuracy of the

Content should not be relied upon and should be independently verified with
primary sources of information. Taylor and Francis shall not be liable for any
losses, actions, claims, proceedings, demands, costs, expenses, damages,
and other liabilities whatsoever or howsoever caused arising directly or
indirectly in connection with, in relation to or arising out of the use of the
Content.
This article may be used for research, teaching, and private study purposes.
Any substantial or systematic reproduction, redistribution, reselling, loan,
sub-licensing, systematic supply, or distribution in any form to anyone is
expressly forbidden. Terms & Conditions of access and use can be found at
http://www.tandfonline.com/page/terms-and-conditions

Mol. Cryst. Liq. Cryst., Vol. 491, pp. 152–163, 2008
Copyright # Taylor & Francis Group, LLC
ISSN: 1542-1406 print=1563-5287 online
DOI: 10.1080/15421400802329590
Thermally Stable Nonlinear Optical Polymers Based
on Polyimides Substituted with Chromophores
Containing Julolidine Moiety
Hyun Kyung Ju1,2, Jong Sun Lim1, Changjin Lee1,
Dong Hoon Choi2, and Dong Wook Kim1
1Advanced Materials Division, Korea Research Institute of Chemical
Technology, Daejeon, Korea
2Department of Chemistry, Korea University, Seoul, Korea
We designed and synthesized a NLO chromophore adopting the concept of shape
modification as well as possessing high thermal stability. The chromophore was
featured by a phenylene ring as a conjugation bridge, a bulky alkyl chain attached
on the side of the conjugation bridge, and julolidine moiety as an electron donor.
The NLO chromophore was attached to the polyimide as a side chain, resulting in
thermally durable NLO polymers. On set decomposition temperature of the NLO
chromophore was measured 330ꢀC in TGA analysis. The NLO polymer exhibited
high glass transition temperature of 150ꢀC and was thermally stable up to
250ꢀC. The polymer was quite soluble in common solvents and produced an optical
quality film by spin-coating. The electro-optic coefficient of the film was measured
using 1.55 lm laser source, giving as high as 30 pm=V at the poling condition of
150ꢀC and 1 MV=cm.
Keywords: electro-optic; julolidine donor; nonlinear optical polymer; thermal stability
INTRODUCTION
Organic and polymeric nonlinear optical (NLO) materials have been
extensively studied as a viable alternative to the conventional inor-
ganic crystalline materials in the telecommunication applications such
as the optical modulators, optical processing devices, etc. In recent
research reports, the optical devices incorporating these materials
demonstrated broad bandwidth over 150 GHz and low driving voltage
less than 1 V [1–4].
Address correspondence to Dong Wook Kim, Advanced Materials Division, Korea
Research Institute of Chemical Technology, Daejeon 305-600, Korea. E-mail: dongwook@
krict.re.kr
152

Thermally Stable Nonlinear Optical Polymers
153
One of the most challenging tasks in this area of research is how to
efficiently translate the molecular hyperpolarizability (b) of the chro-
mophores into the macroscopic electro-optic (EO) activities (r33). The
concept of shape modification of NLO chromophores by incorporating
a bulky side alkyl chain has been introduced to reduce the intermolecu-
lar interaction between the chromophore molecules. The electrostatic
attraction between the neighboring molecules especially in a high load-
ing density might be a main reason for low poling efficiency because it
may act as a strong resistance force against the external poling electric
field. The computer simulation and experimental results have proved
that the shape modification was an efficient way to enhance the poling
efficiency and the macroscopic optical nonlinearity [1(b),3].
Another major quest in the development of device-adaptable NLO
polymers is how to secure enough thermal and oxidative stability to
endure the harsh condition in the device fabrication and maintain
its initial performance through the long-time use over several years
[5–7]. For this aim, we need a chromophore with high thermal
decomposition stability and also a backbone polymer with high glass
transition temperature as well as decomposition stability. Polyene
structure has been commonly adopted for the conjugation bridge of
the NLO chromophores due to its efficient conjugation. However, such
polyene chromophores generally have poor thermal and photo stab-
ility, which is a critical drawback in a commercial application. Aro-
matic rings such as thiophene or phenylene are considered better
alternatives, which are efficient and thermally stable conjugation
bridge [8]. Among many kinds of polymers, polyimides are well known
thermally stable polymers with optical transparency and high Tg.
Hence the polymers have been studied for the NLO backbone polymer
by many researchers [9].
In this work, we designed a NLO chromophore adopting the concept
of shape modification as well as possessing high thermal stability. The
chromophore was featured by a phenylene ring as a conjugation
bridge, a bulky alkyl chain attached on the side of the conjugation
body, and julolidine moiety as an electron donor. Julolidine has a simi-
lar chemical structure with aniline with two N-alkyl substituents
forming rings with aromatic group. The fused ring structure efficiently
protects the amine vulnerable to a radical attack and locks the lone
electron pair of the nitrogen into the conjugation with the aromatic
ring, leading to higher stability and stronger electron donating ability
[10]. The NLO chromophore was chemically attached as a side chain to
the thermally stable polyimide backbone. The resulting NLO polymer
1
was fully characterized by H NMR, UV=Vis absorption spectroscopy,
TGA, DSC, and macroscopic optical nonlinearity.

154
H. K. Ju et al.
EXPERIMENTAL
Materials
Methanesulfonic acid, phosphorus oxychloride, sodium hydride, sodium
iodide, imidazole, tert-butyldimethyl-silyl chloride, n-butyl lithium in
hexane, piperidine, potassium tert-butoxide and triethyl amine were
purchased from Aldrich and used as received. 3-Aminophenol, 1-chloro-
3-methyl-2-butene and 6-bromohexanol were obtained form TCI.
The NLO chromophore (JuOH-TCF) and the NLO polyimide (PI-
Ju) were synthesized by the routes described in Schemes 1 and 2,
respectively.
Synthesis of Compound 1
In a three-necked flask equipped with a nitrogen inlet, a condenser,
and a stirrer, 3-aminophenol (30.0 g, 0.27 mol), 1-chloro-3-methyl-2-
butene (63.2 g, 0.60 mol), sodium acetate (51.9 g, 0.63 mol) and 80 ml
anhydrous DMF were added. The air in the reaction vessel was
replaced by nitrogen and the temperature was maintained at 30ꢀC
SCHEME 1 Synthesis of the NLO chromophore JuOH-TCF.

Thermally Stable Nonlinear Optical Polymers
155
SCHEME 2 Synthesis of the NLO polyimide PI-Ju.
with stirring. After about 12 h, the solution was filtered and the
filtrate was collected. An identical volume of conc. HCl (aq) was added
at 0ꢀC. The residue was filtꢀered, washed with THF several times and
1
then dried in vacuo at 100 C (yield: 55%). H NMR (DMSO, ppm) d
10.12 (broad, ꢁNH), 7.26-7.17 (m, 3H), 6.84 (s, 1H), 5.24-5.19 (t,
J ¼ 6.75 Hz, 2H), 4.07 (s, 4H), 3.80 (broad, ꢁOH), 1.60 (s, 6H), 1.53
(s, 6H).
Synthesis of Compound 2
Compound 1 (24.0 g, 0.85 mol) was added to methanesulfonic acid
(60 ml) and heated to 95ꢀC. After 2 h at this temperature, the mixture
was cooled to 0ꢀC with vigorously stirring. NH4OH(aq) was added until
pH 7–8 was achieved and the solution was filtered. Solid product
was collected and dried in vacuo at 100ꢀC (yield: 80%). 1H NMR
(CDCl3, ppm) d 8.70 (ꢁOH), 6.77-6.74 (d, J ¼ 8.34 Hz, 1H), 6.08-6.05
(d, J ¼ 8.34 Hz, 1H), 2.98-2.94 (t, J ¼ 5.46 Hz, 2H), 2.92-2.89
(t, J ¼ 5.49 Hz, 2H), 1.67-1.64 (m, 4H), 1.33 (s, 6H), 1.15 (s, 6H).
Synthesis of Compound 3
POCl3 (7.0 ml) was slowly added to 10.0 ml anhydrous DMF under
nitrogen at 0ꢀC. The mixture was stirred vigorously for 2 h and then
compound 2 (9.7 g, 0.40 mol) dissolved in 10 ml anhydrous DMF was
added dropwise. After 12 h at room temperature, the solution was
added dropwise to the ice water and then NaOAc(aq) was added
until pH 7–8 was achieved. After vigorous stirring overnight, the
filtrate was collected and recrystallized from ethyl acetate. The
product was filtered and then dried in vacuo at 50ꢀC (yield: 95%).
1H NMR (CDCl3, ppm) d 9.38 (s, 1H), 7.04 (s, 1H), 3.34-3.30 (t,
J ¼ 6.24 Hz, 2H), 3.24-3.20 (t, J ¼ 5.81 Hz, 2H), 1.75-1.71 (m, 4H),
1.44 (s, 6H), 1.25 (s, 6H).

156
H. K. Ju et al.
Synthesis of Compound 4
Compound 3 (16.6 g, 0.06 mol) was dissolved in anhydrous DMF (60 ml)
under nitrogen atmosphere. Sodium hydride (1.84 g, 0.073 mol) in DMF
(35 ml) was slowly added into the solution. After 15 min stirring, 6-bro-
mohexanol (13.2 g, 0.073 mol) and NaI (0.45 g) was added. The mixture
was refluxed at 60ꢀC for 12 h and then cooled to room temperature. The
solution was poured into the water. The organic layer was extracted
with dichloromethane and dried over anhydrous MgSO4. After the sol-
vent was evaporated, a brown solid was obtained by column chromato-
graphy (yield: 77%). 1H NMR (CDCl3, ppm) d 9.92 (s, 1H), 7.57 (s, 1H),
3.98-3.94 (t, J ¼ 6.84 Hz, 2H), 3.69-3.64 (t, J ¼ 6.43 Hz, 2H), 3.31-3.27
(t, J ¼ 5.97 Hz, 2H), 3.24-3.21 (t, J ¼ 5.97 Hz, 2H), 1.94-1.44 (m, 10H),
1.42 (s, 6H), 1.26 (s, 6H).
Synthesis of Compound 5
Compound 4 (17.0 g, 0.046 mol) and imidazole (7.75 g, 0.11 mol) was
dissolved in anhydrous DMF (50 ml) under nitrogen atmosphere.
A solution of tert-butyldimethyl-silyl chloride (8.23 g, 0.055 mol) in
DMF (20 ml) was added dropwise to the above solution. The reaction
mixture was stirred at room temperature for 3 h. The resulting
mixture was poured into the water in a separation funnel and was
extracted with hexane. The hexane extract was then dried over MgSO4
and condensed by a rotary evaporator. The residue was purified by col-
umn chromatography to produce a green liquid in 83% yield. 1H NMR
(CDCl3, ppm) d 9.89 (s, 1H), 7.53 (s, 1H), 3.92-3.87 (t, J ¼ 6.72 Hz, 2H),
3.59-3.54 (t, J ¼ 6.21 Hz, 2H), 3.26-3.22 (t, J ¼ 6.21 Hz, 2H), 3.19-3.15
(t, J ¼ 5.76 Hz, 2H), 1.88-1.37 (m, 12H), 1.35 (s, 6H), 1.21 (s, 6H),
0.84 (s, 9H), 0.00 (s, 6H).
Synthesis of Compound 7
Compound 5 (18.4 g, 0.038 mol) and compound 6 (25.5 g, 0.045 mol; the
synthetic route of the compound 6 was described in our previous paper
[4(d)]) was dissolved in anhydrous THF (50 ml) under nitrogen atmos-
phere. Potassium tert-butoxide (5.79 g, 0.049 mol) in THF (20 ml) was
transferred into the solution. The reaction mixture was stirred at room
temperature for 12 h. The resulting mixture was poured into the satu-
rated NaHCO3. The organic layer was extracted with hexane and then
dried over MgSO4. After the solvent was evaporated, the residue was
purified by column chromatography to produce a green liquid in 86%
1
yield. H NMR (CDCl3, ppm) d 7.30 (s, 1H), 7.15 (s, 2H), 7.11 (s, 1H),

Thermally Stable Nonlinear Optical Polymers
157
7.02 (s, 1H), 3.86-3.79 (m, 6H), 3.55-3.51 (t, J ¼ 6.48 Hz, 2H), 3.14-3.10
(t, J ¼ 5.49 Hz, 2H), 3.07-3.04 (t, J ¼ 4.74 Hz, 2H), 1.85-1.23 (m, 38H),
0.95-0.85 (m, 12H), 0.83 (s, 9H), 0.00 (s, 6H).
Synthesis of Compound 8
Compound 7 (18.7 g, 0.021 mol) was dissolved in anhydrous THF
(50 ml). The solution was cooled to ꢁ84ꢀC and then 2.5 M n-butyl lith-
ium in hexane (2.0 g, 0.031 mol) was added slowly. After the mixture
was stirred for 30 min, dry DMF (3.0 g) was added dropwise as the
reaction temperature maintained at ꢁ84ꢀC. The mixture was stirred
for 3 h below 0ꢀC. After the reaction was completed, the organic layer
was extracted with hexane. The organic layer was dried over MgSO4
and the solvent was evaporated. The residue was purified by column
1
chromatography to produce an orange liquid in 45% yield. H NMR
(CDCl3, ppm) d 10.40 (s, 1H), 7.35 (s, 1H), 7.31 (s, 1H), 7.29 (s, 1H),
7.25 (s, 1H), 7.18 (s, 1H), 3.96-3.84 (m, 6H), 3.87-3.52 (t, J ¼ 6.21 Hz,
2H), 3.18-3.14 (t, J ¼ 5.73 Hz, 2H), 3.11-3.08 (t, J ¼ 5.49 Hz, 2H),
1.88-1.24 (m, 38H), 0.96-0.96 (m, 12H), 0.85 (s, 9H), 0.00 (s, 6H).
Synthesis of Compound 9
Compound 8 (7.0 g, 8.27 mmol) was dissolved in acetone (20 ml). 1N
HCl (10 ml) was added slowly to the solution. The mixture was stirred
for 3 h at room temperature, followed by neutralization with triethyl-
amine (3 ml). The organic layer was washed with water and extracted
with hexane. The residue was purified by column chromatography
to produce an orange liquid in 75% yield. 1H NMR (CDCl3, ppm)
d 10.42 (s, 1H), 7.36 (s, 1H), 7.33 (s, 1H), 7.30 (s, 2H) 7.20 (s, 1H),
3.98-3.87 (m, 6H), 3.61-3.57 (t, 2H), 3.20-3.16 (t, J ¼ 5.94 Hz, 2H),
3.14-3.10 (t, J ¼ 5.67 Hz, 2H), 1.91-1.23 (m, 38H), 0.98-0.90 (m, 12H).
Synthesis of JuOH-TCF
Piperidine (0.41 g, 4.85 mmol) was added into the solution of TCF
(0.74 g, 3.73 mmol) in dry THF (15 ml) and the solution was stirred
at 0ꢀC for 30 min. A solution of compound 9 (2.73 g, 3.73 mmol) in
dry THF (60 ml) was added slowly. The reaction mixture was stirred
at room temperature for 6 h. The mixture was quenched by adding a
small amount of water and THF was removed by a rotary evaporator.
The residue was extracted by ethylacetate. The crude product was
purified by column chromatography to produce a dark blue solid in
1
60% yield. H NMR (CDCl3, ppm) d 8.04-7.98 (d, J ¼ 16.50 Hz, 1H),

158
H. K. Ju et al.
7.44-7.39 (d, J ¼ 16.20 Hz, 2H), 7.34-7.28 (d, J ¼ 16.20 Hz, 1H), 7.16 (s,
1H), 7.08-7.03 (d, J ¼ 14.94 Hz, 2H), 3.98-3.95 (d, J ¼ 3.45 Hz, 4H),
3.89-3.84 (t, J ¼ 6.78 Hz, 2H), 3.63-3.58 (t, J ¼ 6.48 Hz, 2H), 3.24-3.20
(t, J ¼ 5.82 Hz, 2H), 3.16-3.13 (t, J ¼ 5.82 Hz, 2H), 1.86-1.32 (m, 44H),
1.02-0.90 (m, 12H).
Synthesis of NLO Polyimide Substituted
with JuOH-TCF (PI-Ju)
The aromatic polyimide with a hydroxyl functional moiety was
prepared according to the literature by carrying out the condensation
polymerization between 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoro
propane and oxydiphthalic anhydride, followed by imidization reaction
[4(f),6]. The synthesized hydroxyl polyimide was characterized by GPC,
DSC, and TGA. The average molecular weight was found to be 18,000
and the polydispersity index was 1.6 by GPC. Tg of the polymer was
measured 275ꢀC by DSC and the on set degradation was 355ꢀC by TGA.
The NLO chromophore was bonded to the hydroxyl polyimide via
Mitsunobu coupling as depicted in Scheme 2. The diethyl azodicarbox-
ylate (DEAD) (1.14 g, 6.57 mmol) was added dropwise for 4–6 h into the
solution of hydroxyl polyimide, triphenylphosphine (1.72 g, 6.57 mmol),
and JuOH-TCF in THF (64 ml) under nitrogen atmosphere. The reac-
tion mixture was stirred at room temperature for 48 h. The resulting
reaction mixture was precipitated into an agitated solution of meth-
anol. The collected precipitate was dissolved in THF (60 ml) and repre-
cipitated from methanol to purify the polymer. The precipitate was
filtered and washed with methanol. Finally, the soxhlet extraction
was carried out for 3 days to remove any residue of the monomers.
Measurement of Electro-Optic Coefficient
The NLO polyimide was dissolved in cyclopentanone at a concen-
tration of 10–15 wt.%. The solution was spin-coated on ITO glass.
The spincoated films were thoroughly dried in the vacuum oven at
100ꢀC for 3 h. The dark blue films were about 1–2 mm thick. 100 nm-
thick gold electrodes were deposited on the top of the films in a
thermal evaporator. The samples were heated on a hot plate with a
temperature controller to around the glass transition temperature of
the polymer films, remained in the temperature for 5–30 min, and
cooled down to room temperature under the electric field. Electro-optic
coefficient (r33) of the aligned polymer films was measured according
to the reflection technique proposed by Teng and Man using 1.55 mm
laser source [11].

Thermally Stable Nonlinear Optical Polymers
159
RESULT AND DISCUSSION
The synthetic procedure for the NLO chromophore was started with
build-up of the conjugation bridge consisting of the dialkoxy chain sub-
stituted phenyl ring as shown in Scheme 1. 2-Ethylhexyl group was
attached to the bridge to keep the chromophore molecule from
interacting closely with its neighboring ones and hence minimize its
intermolecular electrostatic interaction. The bulky alkyl chains also
play a major role in suppressing formation of cis-isomer as well as
offering good solubility. 3-Aminophenol and 1-chloro-3-methyl-2-
butene reacted to produce compound 1. After cyclization by methan-
sulfonic acid, compound 3 was obtained via Vilsmeier formylation.
As a tethering site to the backbone polymer, hydroxyl group was intro-
duced by reacting 6-bromohexanol to the compound 3. After protecting
the hydroxyl, the julolidine donor was coupled with the phenylene
bridge via Wittig-Horner reaction. The terminal bromide of the com-
pound 7 was converted to aldehyde by treatment with n-butillithium
and DMF according to the Bouveault method. After restoring the
hydroxyl, the resulting compound 9 was combined with the electron
acceptor, 2-(3-cano-4,5,5-trimethyl-5H-furan-2-ylidene)malononitrile
(TCF) in a mild reaction condition using piperidine as a base, to give
FIGURE 1 1H NMR spectrum of JuOH-TCF.

160
H. K. Ju et al.
the final product JuOH-TCF. The chromophore was purified by
column chromatography to yield a dark blue powder.
The NLO chromophore was characterized by 1H NMR, UV=Vis
absorption spectroscopy, DSC, and TGA. The NMR spectrum in
Figure 1 clearly indicated that JuOH-TCF was successfully synthesized
in a high purity. In addition, the coupling constants as large as 16 Hz at
8.02, 7.41, 7.31, and 7.05 ppm clearly indicated that the ethenyl moieties
in the conjugation body had a trans conformation. There was seen no
peak due to cis-conformation as the bulky alkyl chain may suppress
1
FIGURE 2 (a) H NMR spectrum and (b) FT–IR spectrum of the NLO polyi-
mide PI-Ju.

Thermally Stable Nonlinear Optical Polymers
161
the formation of the cis-isomer. The UV=Vis absorption spectrum of the
chromophore in chloroform exhibited a strong absorption band centered
at 665 nm due to the p-p charge transfer in the molecule. The DSC data
of the chromophores exhibited sharp melting peaks at 128ꢀC, indicating
that it was crystalline and highly pure compound. The onset decompo-
sition temperature was also evaluated by TGA. JuOH-TCF was
remained thermally stable up to 330ꢀC.
The hydroxyl polyimide has two hydroxyl groups in the repeat unit,
which would be bonded to the NLO chromophore through Mitsunobu
FIGURE 3 (a) DSC thermogram and (b) TGA thermogram of NLO polyimide
PI-Ju.

162
H. K. Ju et al.
coupling in the presence of triphenyl phosphine and diethyl azodi-
sscarboxylate. The resulting NLO polyimide was purified by repeated
reprecipitation from THF to methanol and soxhlet extraction. The
NLO polyimide was thoroughly characterized by 1H NMR, FT-IR,
DSC, and TGA. The NLO polyimide showed no peak around 10 ppm
in 1H NMR spectrum of Figure 2(a), while the hydroxyl polyimide
had a peak at 10.42 ppm due to the hydroxyl groups, confirming that
all hydroxyls in the backbone were bonded with the NLO chromo-
phore. FT-IR in Figure 2(b) also verified the full conversion since there
was no absorption band around 3300 cmꢁ1 due to the hydroxyl group.
The thermal features of the NLO polyimide were investigated by DSC
and TGA as shown in Figure 3. The NLO polymer exhibited fairly high
glass transition temperature of 150ꢀC as determined by DSC. The TGA
analysis clearly shows that the NLO polyimide was remained ther-
mally durable up to 250ꢀC.
We fabricated optical quality films by spin-coating the solution of the
NLO polyimide in cyclopentanone on the ITO glass. The films were thor-
oughly dried in the vacuum oven at 100ꢀC for 3 h. After gold electrodes
were deposited, the films were heated on a hot plate with a temperature
controller to around the glass transition temperature of the polymer
films, remained in the temperature for 5–30 min, and cooled down to
room temperature under the electric field. Electro-optic coefficient of
the poled polymer films was measured by the reflective technique using
1.55 mm laser source. The NLO polyimide showed as high as 30 pm=V of
electro-optic coefficient at the poling condition of 150ꢀC and 1MV=cm.
CONCLUSION
In this work, we prepared a NLO chromophore adopting the concept of
shape modification as well as possessing high thermal stability and
also incorporated the NLO chromophore into the hydroxyl polyimide,
resulting thermally durable NLO polymers. The NLO polymer exhib-
ited high glass transition temperature of 150ꢀC and was thermally
stable up to 250ꢀC in the DSC and TGA analysis. The optical quality
films obtained from the polymer showed as high as 30 pm=V of macro-
scopic optical nonlinearity at 1.55 mm.
REFERENCES
[1] (a) Lee, M., Katz, H. E., Erben, C., Gill, D. M., Gopalan, P., Heber, J. D., & McgGee,
D. J. (2002). Science, 298, 1401.
(b) Shi, Y., Zhang, C., Zhang, H., Bechtel, J. H., Dalton, L. R., Robinson, B. H., &
Sterier, W. H. (2000). Science, 288, 119.

Thermally Stable Nonlinear Optical Polymers
163
[2] (a) Kim, T.-D., Luo, J., Tian, Y., Ka, J.-W., Tucker, N. M., Haller, M., Kang, J.-W., &
Jen, A. K.-Y. (2006). Macromolecules, 39(5), 1676.
(b) Lee, S. K., Cho, M. J., Yoon, H., Lee, S. H., Kim, J. H., Zhang, Q., & Choi, D. H.
(2004). Macromol. Res., 12(5), 484.
[3] Dalton, L. R. (2003). J. Phys.: Condens. Matter, 15, 897.
[4] (a)Kim, D. W., Hong, S. I., Park, S. Y., & Kim, N. (1997). Bull. Korean Chem. Soc.,
18, 198.
(b) Kim, D. W., Moon, H., Park, S. Y., & Hong, S. I. (1999). Reactive Func. Mater.,
42, 73.
(c) Kim, D. W., Park, S. Y., & Hong, S. I. (1999). Polym. J., 31, 55.
(d) Kim, D. W., Yoon, S. C., Lim, J.-S., & Lee, C. (2007). Opt. Mater., 29, 1423.
(e) Kim, D. W., Choi, J. J., Lim, J.-S., & Lee, C. (2007). Mol. Cryst. Liq. Cryst.,
463, 43.
(f) Ju, H. K., Lim, J.-S., Yoon, S. C., Lee, C., Choi, D. H., Park, S. K., & Kim, D. W.
(2007). Macromol. Symp., 21, 249–250.
[5] Luo, J., Haller, M., Li, H., Tang, H.-Z., Jen, A. K.-Y., Jakka, K., Chou, C.-H., & Shu,
C.-F. (2004). Macromolecules, 37, 248.
[6] Do, J. Y., Park, S. K., Ju, J.-J., Park, S. T., & Lee, M.-H. (2003). Macromol. Chem.
Phys., 204, 410.
[7] He, M., Leslie, T. M., Sinicropi, J. A., Garner, S. M., & Reed, L. D. (2002). Chem.
Mater., 14, 4669.
[8] DeRosa, M. E., He, M., Cites, J. S., Garner, S. M., & Tang, Y. R. (2004). J. Phys.
Chem. B, 108, 8725.
[9] Leng, W., Zhou, Y., Xu, Q., & Liu, J. (2001). Macromolecules, 34, 4774.
(b) Lee, H.-J., Lee, M.-H., Oh, M.-C., & Han, S. G. (1999). Polym. Bull., 42, 403.
[10] Marder, S. R., Cheng, L.-P., Tiemann, B. G., Friedli, A. C., Blanchard-Desce, M.,
Perry, J. W., & Skindhoj, J. (1994). Science, 263, 511.
[11] Teng, C. C. & Man, H. T. (1990). Appl. Phys. Lett., 56, 1734.