Achieving excellent electro-optic activity and thermal stability in poled polymers through an expeditious crosslinking process

Article abstract of DOI:10.1039/c1jm14254b

A series of highly efficient and thermally stable electro-optic (EO) polymers have been developed by poling and crosslinking in situ the blend of high glass-transition temperature (T_g) anthracene-containing polymers and acrylate-functionalized

Full text of DOI:10.1039/c1jm14254b

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PAPER
Achieving excellent electro-optic activity and thermal stability in poled
polymers through an expeditious crosslinking process
Zhengwei Shi,a Jingdong Luo,a Su Huang,a Brent M. Polishak,b Xing-Hua Zhou,a Shawna Liff,c
c
Todd R. Younkin, Bruce A. Block and Alex K.-Y. Jen
c
ab
*
Received 30th August 2011, Accepted 18th October 2011
DOI: 10.1039/c1jm14254b
A series of highly efficient and thermally stable electro-optic (EO) polymers have been developed by
poling and crosslinking in situ the blend of high glass-transition temperature (Tg) anthracene-
containing polymers and acrylate-functionalized dendritic nonlinear optical (NLO) chromophores. By
molecular engineering of the shape, nonlinearity, Tg, and crosslinking moieties of the chromophores
and polymers, the resultant materials showed significantly enhanced EO activities (r33 values as high as
126 pm Vꢀ1 at 1310 nm) and alignment stability (up to 200 ꢁC). Poling efficiency of these EO polymers
could be improved by 35–50% by using simplified lattice hardening and poling protocols. The
combined good processability, large EO activities, and high temperature stability endow these materials
as promising candidates for device exploration in the CMOS-based photonics.
at high temperatures (up to 300 ꢁC) for backend semiconductor
1. Introduction
processing.7–9 Therefore, it is highly desirable to develop poly-
mers with high EO coefficients and thermal stability after poling,
which are compatible with the standard CMOS process to
facilitate photonic integration.
Driven by the rapid growth of global data traffic, optical inter-
connect is under vigorous development as a key enabling tech-
nology for future computer systems and mobile devices due to its
great advantages for high bandwidth and low power consump-
tion.1–3 It is envisioned that the speed of intra- or inter-chip data
communications, such as core-to-core, CPU-to-CPU and CPU-
to-memory, needs to be improved to greater than 40 Gb sꢀ1
within a few years to accommodate the rapidly increasing
amount of data flow.4,5 A viable solution to meet such bandwidth
demands is to integrate optical interconnects with conventional
Recently, it has been demonstrated that significantly enhanced
thermal stability can be achieved by applying the reinforced site
isolation concept to spatially separate highly polarizable but
chemically sensitive dipolar chromophores in a polymer matrix
and then crosslink them in situ during the poling process.10a This
approach has been successfully extended to process multifunc-
tional EO dendrimers and polymers using Diels-Alder (DA)
cycloaddition with properly designed reaction energetics and
kinetics.10b These EO materials exhibit excellent thermal stability
(up to 250 ꢁC, an improvement of greater than 70 ꢁC compared
to those obtained from high Tg guest–host polymers) and high
EO coefficients (r33 values as high as 84 pm Vꢀ1 at the wavelength
of 1310 nm). These important advancements show promise for
finding materials that can meet the severe performance and
process requirements needed for CMOS photonic integration.
However, there are still some critical issues that need to be
resolved during the poling/curing of EO films. These include
relatively low dielectric strength of the composite material prior
to crosslinking, tedious heating/poling profiles, and mismatched
Tgs between chromophore and polymer matrix during poling.
For example, a pre-annealing step is needed to gain enough
dielectric strength to enable poling, followed by incremental
application of the electric field to gradually orient the dipolar
chromophores without inducing dielectric breakdown. This pre-
annealing process reduces the rotational freedom of chromo-
phores in the matrix prior to cross-linking thus limiting the
poling efficiency in crosslinked EO films.11 For high Tg
silicon-based
complementary
metal-oxide-semiconductor
(CMOS) chips.6 In such a hybrid system, electro-optic (EO)
polymers could be used as active materials for ultrahigh-speed
optical modulation that silicon alone is unable to deliver.
One example is the recently reported ‘‘photo-CMOS’’ plat-
form.6 In this instance a monolithic optical layer integrated on
top of the existing CMOS chip is proposed, where the EO
polymer functions as the active clad of the silicon nitride ring
resonator, optically modulating the signal transmitted through
a nearby silicon nitride waveguide. The main challenge posed
here or in other hybrid systems with CMOS is to develop an
active material system that not only has large EO activity to
ensure low voltage operation of devices, but also can maintain
the polar order in poled polymer films after short time excursion
aDepartment of Materials Science and Engineering, University of
Washington, Seattle, Washington, 98195, USA. E-mail: ajen@u.
washington.edu.; Fax: +1 206 543 3100; Tel: +1 206 543 2626
bDepartment of Chemistry, University of Washington, Seattle, WA, 98195,
USA
cIntel Corporation, Components Research, Hillsboro, OR, 97124, USA
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crosslinkable EO polymers, the effectiveness of reinforced site
isolation is strongly dependent on the optimization of several key
parameters such as: (1) structural flexibility/rigidity of cross-
linkers, (2) compatibility of different components, (3) onset
temperature of DA reactions or cross-linking, and (4) actual Tg
of the polymers. If one of these parameters is neglected,
a compromise in EO performance is likely.
chain polymers (P1 and P2, Scheme 2) to investigate optimal
poling and cross-linking conditions for these materials. Among
the systems studied, the thermoset based on C3 and P2 showed
both good processability/stability and very large r33 value (as
high as 126 pm Vꢀ1 at 1310 nm).
To alleviate this problem, we have been focusing on the
development of simplified processing protocols to achieve ther-
mally stable EO materials. In this work, acrylate-containing
dendronized NLO chromophores (C1, C2 and C3, Scheme 1)
were dispersed into anthracene-containing cross-linkable side-
2. Results and discussion
2.1 Synthesis and characterization
Three acrylate-containing dendronized chromophores C1–C3
were designed and synthesized to study the effect of reinforced
Scheme 1 Synthesis of acrylate-based dendron-functionalized cross-linkable NLO chromophores C1, C2 and C3.
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Scheme 2 Synthesis of cross-linkable polymers P1 and P2.
site isolation on poling and crosslinking of these materials in
anthryl-containing side-chain polymers (Scheme 1). It is note-
worthy that chromophore C1 is based on the structure of the
AJL8-type chromophore, which exhibits a good combination of
relatively large molecular hyperpolarizability (b values around
4000 ꢂ 10ꢀ30 esu at 1.907 mm) and excellent thermal stability
(with the onset decomposition temperature above 230 ꢁC).10a
Furthermore, chromophores C2 and C3 are based on the
(4-dialkylamino)phenyltetraene conjugating bridge terminated
with a strong acceptor (CF3–TCF). This type of phenyltetraenic
chromophore is known to possess very large molecular hyper-
polarizabilities (b values over 6000 ꢂ 10ꢀ30 esu at 1.907 mm), but
has rather limited thermal stability.14
2.43. P2 was prepared through the Steglich esterification between
9-anthracenepropanoic acid and the pendant phenolic group on
polymer i-15, which was prepared by random radical polymeri-
zation of a 1 : 1 mixture of N-(4-hydroxyphenyl)maleimide and
a-methylstyrene. The intensity of phenol infrared (IR) peaks at
ꢃ3200 cmꢀ1 decreased significantly after anthryl functionaliza-
tion, indicating effective termination of the phenolic groups.
Furthermore, the presence of the anthryl absorption bands at
350–400 nm in the ultraviolet-visible (UV-Vis) spectrum verifies
the successful incorporation of anthryl groups on P2. The result
from GPC showed that P2 has an Mn of ꢃ25 000 Da with
ꢁ
a polydispersity of 2.20. The DSC of P2 (ramping rate, 10 C
minꢀ1, under nitrogen) reveals that this polymer possesses
ꢁ
As shown in Scheme 1 for the detailed synthetic procedure of
these cross-linkable chromophores, C1 was prepared from the
Steglich esterification of the corresponding dihydroxyl precursor
(i-2) using 1,3-diisopropanylcarbodiimide (DIPC) as the
condensation reagent.12,13 However, due to high chemical sensi-
tivity of the CF3–TCF acceptor, the same synthetic route for C1
cannot be directly applied to prepare C2 and C3. The acrylate-
containing dendrons have to be functionalized onto dia-
lkylaminophenyltrienals i-8 and i-11 through the DIPC-mediated
esterification. The resultant bridge precursors i-9 and i-12 were
then condensed with CF3–TCF acceptor at the final stage to
afford cross-linkable chromophores C2 and C3, respectively.15 It
is worth noting that chromophore C3 possesses enhanced
molecular hyperpolarizability because of the stronger 1,2,3,4-
tetrahydroquinoline (THQ) donor.16
a relatively high Tg of 215 C.
2.2 Characterization of thermal stability
The dendritic cross-linkable chromophores C1, C2, and C3 are
all amorphous molecular glasses in the solid state, as shown in
the DSC thermo-diagrams (Fig. 1). The Tgs of C1, C2, and C3
are 87, 84, and 102 ꢁC, respectively. The slightly higher Tg of C3
is likely due to the rigid ring-locked THQ moiety on the central
P1, (poly[(methyl methacrylate)-co-(9-anthracenyl methyl
methacrylate)]), was obtained directly through radical polymer-
ization using 2,20-azobis(isobutyronitrile) (AIBN) as the initiator
(Scheme 2). The molar ratio of anthracene on polymer was
1
controlled to be ꢃ30% (confirmed by H NMR) to maintain
proper cross-linking density after reacting with doped chromo-
phores to ensure that desirable thermal stability, poling effi-
ciency, and optical transparency could be achieved. The result
from the DSC study showed that the resulting polymer has
a moderate Tg of 135 ꢁC. The number-average molecular weight
(Mn) of this polymer was determined to be ꢃ37 000 Da by gel-
permeation chromatography (GPC) with a polydispersity of
Fig. 1 Thermal analysis for C1–C3 by differential scanning calorimetry
(DSC) at a ramp rate of 10 ꢁC minꢀ1 under nitrogen.
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chromophore framework.16 Since a Tg mismatch between poly-
mer and chromophore components often impedes effective
chromophore orientation during electric field poling, this
enhanced Tg on C3 can potentially improve the poling compat-
ibility between P2 and C3 with respect to C1 and C2. The thermal
decomposition temperatures of chromophores C1, C2, and C3
are all around 175 ꢁC. By considering that the acrylate group
could be readily polymerizable by radicals under elevated
temperatures and the highly polarizable dipolar chromophore is
very sensitive to radicals,17,18 the decomposition of chromo-
phores C1, C2, and C3 is likely due to radical attacks at conju-
gated chromophores during curing.
and 390 nm decreased considerably after crosslinking, indicating
DA reaction took place in chromophore-doped crosslinkable
polymers. All thin films derived from P1 and P2 showed <10%
decrease in absorbance after being cured at 200 ꢁC for 30 min (as
shown in Fig. 3, left), while the absorbance of pure chromo-
phores C1, C2, and C3 decreased dramatically after their corre-
sponding films were cured at 175 ꢁC for only 15 min (as shown in
Fig. 3, right). In addition, it is noteworthy that the films derived
from chromophores C1, C2, and C3 possess significantly
improved mechanical properties and excellent solvent resistance
after curing. These results suggest that highly reactive radicals
generated from heating peripheral acrylate moieties during
crosslinking will decompose chromophores and form less
conjugated species. These results are in line with our previous
DSC studies and it also proves that reinforced site isolation is an
effective way to enhance thermal stability of polymeric EO
materials for high temperature device applications.
Both crosslinkable polymers P1 and P2 show good compati-
bility with highly polarizable chromophores. To study thermal
stability of chromophores in the solid state, chromophores C1,
C2, and C3 were formulated with P1 and P2 separately in 1,1,2-
trichloroethane (TCE). The concentration of the chromophore in
these polymer composites was maintained at ꢃ17 wt% by
controlling the molar ratio (1 : 1) of anthracene and acrylate
moieties in the composites. These solutions were spin-coated
onto glass substrates and baked overnight at 60 ꢁC under
vacuum to afford optical quality thin films. The DSC results
(Fig. 2) showed that the onset cross-linking temperatures (Tx) of
2.3 Poling study and EO properties of crosslinkable polymers
To study poling and EO properties of these crosslinkable poly-
mers, C1, C2, and C3 were individually mixed with P1 and P2 in
TCE to form solutions with 9 wt% solid content. The solutions
were filtered through 0.2 mm PTFE syringe filters, and then spin-
coated onto ITO-coated glass substrates to afford micrometre-
thick films with good optical quality. The ratio of mixing was
calculated to keep equal molar ratios of anthryl and acrylate
groups in the composites. After baking overnight at 60 ꢁC under
vacuum to remove residual solvent, a thin layer of gold was
sputtered onto the films to serve as the top electrode for contact
poling. Both the poling fields and leak through currents (LTCs)
were monitored to optimize the entire process.
ꢁ
both polymer composites (P1 and P2) are around 120–140 C.
These are similar to the values previously reported for EO den-
drimers.10 Results from DSC also showed substantially improved
thermal stability for chromophores (C1–C3) due to better site
isolation, which prevents decomposition via bimolecular reac-
tions. After crosslinking, the onset decomposition temperature
(Tdec in second heating) of material composites increased
ꢁ
significantly to ꢃ245 C, which is comparable to the previously
reported binary dendrimer analogues.10a
Thermal stability of the polymer composites was further
investigated by monitoring the absorption intensity of the thin
film UV-Vis absorption spectra after heating these films
isothermally at elevated temperatures. This study was designed
to quantify the amount of chromophore decomposition. The
intensity of typical anthryl absorption bands located at 350, 370,
Fig. 4 compares the poling profiles of previously reported
binary dendronized molecules and the crosslinkable polymer
composites based on P2. Due to low dielectric breakdown
threshold, the electric field that can be applied onto the binary
dendronized molecules is quite limited.10a As a result, after films
were mounted on the poling stage at 50 ꢁC, the initial field
strength can only be set at 10 V mmꢀ1. The temperature was then
ramped up with a rate of 10 ꢁC minꢀ1 to 140 ꢁC, where the LTCs
started to increase rapidly. The temperature was carefully held at
140 ꢁC to avoid catastrophic breakdown.19,20 Meanwhile, the
LTCs leveled off due to significantly enhanced dielectric strength
of films upon DA crosslinking. The applied field was then slowly
increased to 100 V mmꢀ1 by monitoring the poling current. The
ꢁ
films were finally heated to 190 C to facilitate further chromo-
phore orientation and crosslinking. This protocol usually takes
more than 30 min. It is noted that poling efficiency could be
compromised considerably in this process, since the dielectric
strength gained at the low temperature zone by pre-crosslinking
significantly reduces the rotational freedom of dipolar
chromophores.
Unlike binary dendronized chromophores, poling based on the
blend of dendritic chromophores and P2 can be performed in
a more simplified manner by directly applying a high electric field
of 100 V mmꢀ1 to the uncured films to orient the dipolar chro-
mophores as the poling process begins. This is because higher
initial dielectric strength and mechanical properties of the
dendritic chromophore/polymer blends (such as P2/C3) give
Fig. 2 Thermal analysis of P2, C2, and P2/C2 before and after curing by
differential scanning calorimetry (DSC) at a ramp rate of 10 ꢁC minꢀ1
under nitrogen.
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Fig. 3 UV-Vis-NIR absorption spectra of the thin films P1/C2 (left) and C2 (right) upon thermal curing. Note that these spectra are normalized to the
initial absorption peak.
EO activities (r33) of the poled/cured films were measured by
using the Teng–Man simple reflection technique at the wave-
length of 1.31 mm after the samples were cooled to room
temperature and the poling field was removed.21 Poling condi-
tions and measured r33 values of these polymers are summarized
in Table 1. Fairly large r33 values of 42 pm Vꢀ1 and 86 pm Vꢀ1
could be obtained for P1/C1 and P1/C2, respectively. This result
indicates that the new poling protocol significantly enhances the
poling efficiency of crosslinkable polymers, which is comparable
to the typical guest–host polymers.10a,14a Furthermore, consid-
ering the much lower chromophore content compared to previ-
ously reported binary EO dendrimers,10a these crosslinkable
polymers show improved poling efficiency by 35–50%. Cross-
linkable polymers based on P2 show r33 values of 33 pm Vꢀ1, 68
Fig. 4 Poling profile and monitored current flow for (A) binary
pm Vꢀ1, and 126 pm Vꢀ1 for P2/C1, P2/C2, and P2/C3, respec-
dendronized molecules10a and (B) cross-linkable EO polymer P2/C3.
tively. P2/C1 and P2/C2 showed slightly lower r33 values
compared to the samples based on P1. This can be explained
lower LTCs during the poling/curing process. This also avoids
damages to the films. The ability to apply full field strength in the
beginning of the poling process is very critical for achieving
efficient orientation of chromophores since it allows more rota-
tional freedom for chromophores before crosslinking. Therefore,
a much simplified protocol can be used for these materials, and
the entire process can be finished within 5–7 min.
because P2 has a higher Tg, thus these samples need to be poled at
a much higher temperature (195 ꢁC vs. 135 ꢁC). However, the
poled film derived from P2/C3 shows a much larger r33 (126 pm
Vꢀ1). This is the result of higher intrinsic molecular hyper-
polarizability of the chromophore (better electron-donating THQ
was used as donor)16 and better compatibility between polymer
and chromophore since they have a smaller Tg difference.
Table 1 Summary of the physical properties of cross-linkable NLO polymers
c
Tg /ꢁC
b
Host
polymer
NLO
chromophore
Dye
contenta (wt%)
lmax
nm
/
Thermal
stabilityd (%)
Poling
voltagee/V mmꢀ1
Poling
temp.e/ꢁC
r33f @ 1.31
mm/pm Vꢀ1
c
Host
135
Guest
Tdec /ꢁC
P1
P2
C1
C2
C1
C2
C3
16.7
17.5
16.4
17.2
17.6
23.0
704
769
707
772
853
709
87
84
87
84
102
—
258
253
257
255
270
268
93
91
93
90
93
89
100
110
100
100
100
100
135
135
195
190
185
120
42
86
33
68
126
44
215
EO dendrimer10a
—
a
b
Net weight percentage of chromophore within polymers. The wavelengths of the absorption maxima. Analytic results of Differential Scanning
c
Calorimetry (DSC) at the heating rate of 10 ꢁC minꢀ1 on thermo-equilibrated samples: Tg, glass transition temperatures; Tdec, onset decomposition
temperatures. The residual percentage of chromophore after thin films was isothermally cured. The chromophore content was quantified by the
d
e
absorbance of the film at lmax. Duration of curing: 30 min. All the poling studies were performed by applying the full voltages at the beginning,
f
then ramped the temperature from 25 ꢁC to the optimal poling temperatures rapidly. Electro-optic coefficients measured by a simple-reflection
technique.
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recorded on a Bruker Daltonics Esquire ion trap mass spec-
trometer. Glass transition temperatures (Tg) were measured by
differential scanning calorimetry (DSC) using a DSC2010 TA
instrument with a heating rate of 10 C minꢀ1. Elemental anal-
ꢁ
yses were performed by Intertek QTI Laboratory (Whitehouse,
NJ). Compounds i-1, i-4, i-10, i-11, i-13, i-14, and i-16 were
obtained according to the literature procedures with only minor
modifications.11,12
Preparation of chromophore i-2
To a solution of i-1 (1.48 g, 2 mmol) in 25 mL of THF was added
10 mL of HCl (6 N). The solution was stirred at room temper-
ature for 4 h, then neutralized with saturated NaHCO3 solution.
After extracting with ethyl acetate several times, the organic
layers were combined, washed with water, and dried over
Na2SO4. After concentrating under reduced pressure, compound
i-2 was precipitated from methanol, collected by filtration, and
dried under high vacuum. The resultant compound was directly
used for the next step without further purification as a deep green
solid (1.06 g, 94%). 1H NMR (300 MHz, acetone, TMS, d ppm):
8.42 (d, J ¼ 15.6 Hz, 1H), 7.52 (s, 1H), 7.45 (d, J ¼ 8.7 Hz, 2H),
7.26 (d, J ¼ 15.6 Hz, 1H), 7.19 (d, J ¼ 15.6 Hz, 1H), 6.81 (d, J ¼
8.7 Hz, 2H), 6.69 (d, J ¼ 15.6 Hz, 1H), 4.78 (d, J ¼ 5.4 Hz, 2H),
3.75 (t, J ¼ 6.3 Hz, 2H), 3.64 (t, J ¼ 6.3 Hz, 2H), 3.54 (q, J ¼ 7.0
Hz, 2H), 2.08 (s, 3H), 1.26 (t, J ¼ 7.0 Hz, 3H). ESI-MS (m/z):
calcd: 566.1; found: 566.6.
Fig. 5 The temporal stability of the poled films P2/C1, P2/C2, and P2/
C3 at the curing temperature of 150 ꢁC.
All these poled samples showed very promising long-term
alignment stability under high temperature annealing. For
example, after the poled samples of P2/C1, P2/C2, and P2/C3
were annealed at 150 ꢁC for 500 h, about 76–88% of the initial r33
values could be still kept (Fig. 5). More importantly, these poled
samples could survive short temperature excursion at 200 ꢁC for
30 min and still kept ꢃ80% of their initial poling-induced r33
values. This demonstrates that these molecular-engineered EO
materials can be used to facilitate poling and lattice hardening to
improve both their EO activities and thermal stability.
Preparation of chromophore C1
The solution of compound i-2 (0.70 g, 1.23 mmol), compound i-3
(0.74 g, 2.82 mmol), and 4-(dimethylamino)pyridinium-4-tolue-
nesulfonate (DPTS, 0.10 g, 0.35 mmol) in THF (25 mL) was
stirred at room temperature overnight after the slow addition of
diisopropylcarbodiimide (DIPC, 0.42 g, 2.65 mmol) under
nitrogen atmosphere. The solution was stirred at room temper-
ature for 12 h. After filtering the resultant urea, the solvent was
evaporated under reduced pressure. The crude product was
purified by column chromatography using ethyl acetate and
hexane (1 : 3, v/v) as the eluent to afford dendritic chromophore
3. Conclusion
A series of highly efficient and thermally stable EO polymers
have been developed by poling and crosslinking in situ high Tg
anthracene-containing polymers and acrylate-functionalized
dendritic NLO chromophores. Through careful molecular engi-
neering of shape, nonlinearity, Tgs, and crosslinking moieties of
chromophores and polymers, the resultant materials showed
significantly enhanced EO activities (as high as 126 pm Vꢀ1 at
1310 nm) and temporal stability (as high as 200 ꢁC). Due to
simplified lattice hardening and poling protocols, poling effi-
ciency of these EO polymers is ꢃ35 to 50% higher than previ-
ously reported dendritic chromophore crosslinkable systems.
The combined facile processability, large EO activities, and high
temperature stability showed these materials can be promising
candidates for device exploration in the CMOS-based photonics.
1
C1, as a deep green solid (0.99 g, 76%). H NMR (300 MHz,
CDCl3, TMS, d ppm): 8.09 (d, J ¼ 15.6 Hz, 1H), 7.76 (d, J ¼ 2.1
Hz, 2H), 7.71 (d, J ¼ 2.1 Hz, 2H), 7.57 (s, 1H), 7.47 (d, J ¼ 9.0
Hz, 2H), 7.27 (d, J ¼ 3.3 Hz, 2H), 7.20 (d, J ¼ 3.3 Hz, 2H), 6.82
(d, J ¼ 9.0 Hz, 2H), 6.68 (m, 4H), 6.60 (d, J ¼ 15.6 Hz, 1H), 6.37
(m, 4H), 6.09 (m, 4H), 5.43 (s, 2H), 4.45 (t, 2H), 3.77 (t, 2H), 3.54
(m, 2H), 1.95 (s, 3H), 1.28 (t, J ¼ 6.9 Hz, 3H). 13C NMR: 175.12,
164.85, 164.39, 163.88, 163.85, 162.43, 154.93, 151.10, 151.00,
149.13, 146.36, 138.27, 136.41, 135.54, 133.75, 133.64, 131.91,
131.39, 129.60, 129.55, 127.35, 127.28, 123.64, 123.26, 120.99,
120.71, 120.61, 120.43, 120.35, 115.66, 112.19, 111.45, 111.18,
110.96, 110.60, 97.46, 94.11, 93.85, 62.62, 59.20, 58.38, 48.57,
45.45, 19.18, 12.42. ESI-MS (m/z): calcd: 1054.2; found: 1054.8.
Anal. Calcd for C55H41F3N4O13S: C, 62.62; H, 3.92; N, 5.31.
Found: C, 62.68; H, 4.24; N, 5.04%.
4. Experimental section
Materials and general characterization method
All reactions were carried out under the inert nitrogen atmo-
sphere unless otherwise specified. Dichloromethane (CH2Cl2)
and tetrahydrofuran (THF) were distilled over calcium hydride
and sodium, respectively, and stored under nitrogen prior to use.
All chemicals from Aldrich were used as received unless other-
1
wise specified. H NMR and 13C NMR spectra were taken on
Preparation of compound i-5
a Bruker AV-500 spectrometer (500 MHz) unless otherwise
specified. UV-Vis-NIR spectra were obtained on a Perkin-Elmer
Lambda-9 spectrophotometer while ESI-MS spectra were
To a round bottom flask with ethylene glycol (30 mL) was added
a carefully chopped small piece of sodium metal (0.31 g, 12.96
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ꢁ
mmol) under nitrogen atmosphere. The solution was vigorously
stirred at room temperature until the sodium was completely
dissolved, followed by the addition of isophorone oxide (2.00 g,
12.96 mmol). The mixture became dark shortly and was stirred at
room temperature for another 1 h. Compound i-4 (3.10 g, 13
mmol) was added to this solution mixture and then heated at 65
ꢁC for 18 h. After removing solvent under reduced pressure, the
residue was purified by column chromatography on silica gel
using ethyl acetate and hexane (1 : 2, v/v) to give a red solid, i-5
After the mixture was stirred at ꢀ78 C for 2 h, wet silica gel
(ꢃ4.0 g) with 10.0 mL of diethyl ether was added and the reaction
mixture was stirred at 0 ꢁC for 15 min. After most of the low
boiling solvents were roto-evaporated, the residual mixture was
purified by flash chromatography on silica gel using ethyl acetate
and hexane (1 : 2, v/v) to give compound i-7 as a red solid (1.29 g,
73%). 1H NMR (300 MHz, CDCl3, TMS, d ppm): 10.08 (d, J ¼
8.1 Hz, 1H), 7.39 (d, J ¼ 8.7 Hz, 2H), 7.35 (d, J ¼ 16.5 Hz, 1H),
6.72 (d, J ¼ 16.5 Hz, 1H), 6.65 (d, J ¼ 8.7 Hz, 2H), 6.34 (d, J ¼
8.1 Hz, 1H), 4.63 (s, 2H), 3.95 (t, J ¼ 6.0 Hz, 2H), 3.85 (q, J ¼ 6.0
Hz, 2H), 3.76 (t, J ¼ 6.0 Hz, 2H), 3.56 (t, J ¼ 7.0 Hz, 2H), 3.46 (q,
J ¼ 7.0 Hz, 2H), 3.36 (s, 3H), 2.75 (s, 2H), 2.42 (s, 2H), 1.20 (t, J
¼ 7.0 Hz, 3H), 1.07 (s, 6H). 13C NMR: 195.78, 148.64, 146.19,
142.09, 136.13, 129.14, 124.05, 118.01, 111.67, 96.66, 75.61,
65.27, 61.80, 55.26, 51.41, 50.04, 45.44, 38.82, 32.73, 28.41, 12.17.
ESI-MS (m/z): calcd: 443.2; found: 444.3.
1
(4.10 g, 75%). H NMR (CDCl3, TMS, d ppm): 7.44 (d, J ¼ 8.5
Hz, 2H), 7.28 (d, J ¼ 16.5 Hz, 1H), 6.92 (d, J ¼ 16.5 Hz, 1H), 6.71
(d, J ¼ 8.5 Hz, 2H), 4.66 (s, 2H), 4.01 (t, J ¼ 6.0 Hz, 2H), 3.83 (q,
J ¼ 6.0 Hz, 2H), 3.74 (t, J ¼ 6.0 Hz, 2H), 3.60 (t, J ¼ 7.0 Hz, 2H),
3.50 (q, J ¼ 7.0 Hz, 2H), 3.39 (s, 3H), 2.60 (s, 2H), 2.44 (s, 2H),
1.28 (t, J ¼ 7.0 Hz, 3H), 1.22 (s, 6H). 13C NMR: 195.83, 146.30,
142.02, 136.11, 129.16, 124.10, 118.10, 111.71, 96.75, 65.32,
61.92, 55.33, 51.49, 50.11, 45.50, 38.92, 32.81, 28.48, 12.21. ESI-
MS (m/z): calcd: 417.2; found: 418.3.
Preparation of compound i-8
To a stirred solution of i-7 (0.89 g, 2 mmol) in THF (25 mL) was
added 10 mL of HCl (6 N). The reaction mixture was stirred at
room temperature for 4 h then neutralized with saturated
NaHCO3 solution. The organic layer was washed with water,
and dried over Na2SO4. After concentrating under reduced
pressure, a reddish solid was obtained by flash chromatography
on silica gel using ethyl acetate and hexane (2 : 1, v/v) (0.59 g,
73%). 1H NMR (CDCl3, TMS, d ppm): 10.11 (d, J ¼ 8.0 Hz, 1H),
7.43 (d, J ¼ 8.5 Hz, 2H), 7.38 (d, J ¼ 16.0 Hz, 1H), 6.76 (d, J ¼
8.5 Hz, 2H), 6.74 (d, J ¼ 16.5 Hz, 1H), 6.36 (d, J ¼ 8.5 Hz, 1H),
3.99 (t, J ¼ 6.0 Hz, 2H), 3.87 (m, 4H), 3.53 (t, J ¼ 7.0 Hz, 2H),
3.49 (q, J ¼ 7.0 Hz, 2H), 2.79 (s, 2H), 2.45 (s, 2H), 1.22 (t, J ¼ 7.0
Hz, 3H), 1.09 (s, 6H). 13C NMR: 191.43, 151.97, 148.51, 147.79,
133.49, 133.08, 128.68, 125.01, 121.39, 119.39, 112.18, 74.51,
62.04, 60.02, 52.29, 45.53, 39.07, 38.79, 30.73, 28.26, 12.05. ESI-
MS (m/z): calcd: 399.2; found: 400.3.
Preparation of compound i-6
A solution of freshly distilled acetonitrile (2.00 g, 48.6 mmol)
and dry THF (50 mL) was cooled to ꢀ78 ꢁC and was maintained
at this temperature during the dropwise addition of n-BuLi in
hexane (ꢃ2.4 M, 20 mL, ꢃ48.0 mmol). After the mixture had
ꢁ
ꢁ
been stirred at ꢀ78 C for 15 min, it was warmed to 0 C and
held for 15 min. The solution was cooled back to ꢀ78 ꢁC again,
and kept at this temperature during the dropwise addition of
a solution of compound i-5 (2.50 g, 6.0 mmol) in dry THF (15.0
mL). After the removal of the dry-ice/acetone cooling bath, the
reaction mixture was allowed to warm to 0 ꢁC over 10 min, and
then quenched by adding 10 mL of water. After most of the
solvent was removed under reduced pressure, the residue was
extracted with ethyl acetate (3 ꢂ 50 mL). The combined organic
layer was washed sequentially with brine (2 ꢂ 30 mL) and DI
water (50 mL), and then dried over Na2SO4, filtered, and
evaporated to give the crude product of carbinol intermediate. It
Preparation of compound i-9
ꢁ
was dissolved in glacial acetic acid (12 mL) and stirred at 70 C
for 2 h. The reaction mixture was then diluted by CH2Cl2 (12
mL), and neutralized by saturated aqueous solution of sodium
bicarbonate. The organic layer was collected, dried, concen-
trated, and purified by flash chromatography on silica gel using
ethyl acetate and hexane (1 : 2, v/v) to give compound i-6 as an
orange solid (2.30 g, 87%). 1H NMR (CDCl3, TMS, d ppm): 7.37
(d, J ¼ 9.0 Hz, 2H), 7.18 (d, J ¼ 16.5 Hz, 1H), 6.68 (d, J ¼ 16.5
Hz, 1H), 6.67 (d, J ¼ 9.0 Hz, 2H), 5.80 (s, 1H), 4.65 (s, 2H), 3.93
(t, J ¼ 6.0 Hz, 2H), 3.80 (q, J ¼ 6.0 Hz, 2H), 3.71 (t, J ¼ 6.0 Hz,
2H), 3.58 (t, J ¼ 7.0 Hz, 2H), 3.47 (q, J ¼ 7.0 Hz, 2H), 3.37 (s,
3H), 2.55 (s, 2H), 2.38 (s, 2H), 1.20 (t, J ¼ 7.0 Hz, 3H), 1.05 (s,
6H). 13C NMR: 153.8, 148.64, 146.19, 142.09, 136.13, 129.14,
124.05, 118.01, 111.67, 96.66, 65.27, 61.80, 55.26, 51.41, 50.04,
45.44, 38.82, 32.73, 28.41, 12.17. ESI-MS (m/z): calcd: 440.6;
found: 441.5.
The solution of compound i-8 (0.50 g, 1.25 mmol), compound i-3
(0.74 g, 2.82 mmol), and DPTS (0.10 g, 0.35 mmol) in CHCl3 (15
mL) was stirred at room temperature overnight after the addition
of DIPC (0.42 g, 2.65 mmol) slowly under nitrogen atmosphere.
After filtering the resultant urea carefully, all of the solvent was
evaporated under reduced pressure. The crude product was
purified by column chromatography on silica gel using ethyl
acetate and hexane (1 : 3, v/v) as the eluent to afford i-9 as a light
red solid (0.92 g, 83%). 1H NMR (CDCl3, TMS, d ppm): 10.11 (d,
J ¼ 8.0 Hz, 1H), 7.84 (s, 1H), 7.72 (s, 1H), 7.35–7.28 (m, 6H),
6.72 (d, J ¼ 14.5 Hz, 1H), 6.695–6.60 (m, 7H), 6.42–6.29 (m, 5H),
6.09–6.03 (m, 4H), 4.66 (t, J ¼ 4.0 Hz, 2H), 4.49 (t, J ¼ 6.0 Hz,
2H), 4.10 (t, J ¼ 4.0 Hz, 2H), 3.71 (t, J ¼ 6.0 Hz, 2H), 3.47 (q, J ¼
7.0 Hz, 2H), 2.76 (s, 2H), 2.42 (s, 2H), 1.20 (t, J ¼ 7.0 Hz, 3H),
1.09 (s, 6H). 13C NMR: 190.87, 169.13, 164.81, 164.79, 163.80,
163.70, 153.70, 151.02, 150.99, 150.93, 150.87, 147.92, 147.55,
138.76, 133.54, 133.51, 133.35, 133.16, 132.01, 131.97, 128.60,
127.38, 127.33, 125.01, 121.72, 120.50, 120.38, 120.36, 120.25,
119.16, 117.60, 117.43, 111.86, 70.63, 64.61, 62.70, 60.40, 49.60,
48.50, 45.32, 42.99, 39.14, 38.88, 30.79, 28.28, 23.49, 22.08, 20.73,
14.21, 12.34. ESI-MS (m/z): calcd: 887.3; found: 888.2.
Preparation of compound i-7
The solution of compound i-6 (1.76 g, 4.0 mmol) in freshly dried
toluene (25.0 mL) was cooled to ꢀ78 ꢁC and slowly added
a solution of DIBAL-H in hexane (1.0 M, 10.0 mL, 10.0 mmol).
This journal is ª The Royal Society of Chemistry 2012
J. Mater. Chem., 2012, 22, 951–959 | 957

View Article Online
Preparation of chromophore C2
132.01, 131.66, 131.23, 130.12, 129.61, 127.33, 127.29, 127.25,
126.74, 126.66, 124.06, 123.73, 123.39, 120.96, 120.50, 120.45,
120.34, 120.27, 120.03, 116.66, 113.45, 111.64, 111.47, 110.93,
95.65, 95.31, 71.62, 64.35, 62.95, 57.40, 55.20, 46.23, 43.22, 40.09,
39.38, 31.12, 31.11, 29.66, 28.58, 28.54, 27.94, 27.90, 26.79, 25.03,
20.16, 19.91. ESI-MS (m/z): calcd: 1178.4; found: 1179.5. Anal.
Calcd for C66H61F3N4O14: C, 66.55; H, 5.16; N, 4.70. Found: C,
66.45; H, 4.93; N, 4.54%.
Compound i-9 (0.44 g, 0.5 mmol) and compound i-10 (0.14 g,
0.55 mmol) were mixed with anhydrous ethanol (3 mL). The
mixture was allowed to stir at 65 ꢁC for 30 min and the reaction
progress was monitored by thin layer chromatography (TLC).
The solvent was removed under vacuum and the residual mixture
was purified by flash chromatography on silica gel using ethyl
acetate and hexane (1 : 4, v/v) to give chromophore C2 as a deep
green solid (0.43 g, 78%). 1H NMR (CDCl3, TMS, d ppm): 8.36
(dd, J ¼ 14.5 Hz, 1H), 7.79 (m, 2H), 7.71 (s, 1H), 7.36–7.27 (m,
6H), 6.90–6.82 (m, 2H), 6.66–6.60 (m, 6H), 6.36–6.27 (m, 4H),
6.16 (d, J ¼ 14.5 Hz, 1H), 6.11 (m, 4H), 4.70 (t, J ¼ 6.3 Hz, 2H),
4.49 (t, J ¼ 6.3 Hz, 2H), 4.17 (t, J ¼ 6.3 Hz, 2H), 3.74 (t, J ¼ 6.3
Hz, 2H), 3.49 (q, J ¼ 6.9 Hz, 2H), 2.55 (s, 2H), 2.51 (s, 2H), 1.23
(t, J ¼ 6.9 Hz, 3H), 1.09 (s, 6H). 13C NMR: 175.85, 164.90,
164.74, 163.91, 163.84, 162.33, 151.19, 151.14, 151.06, 148.90,
146.06, 138.47, 136.54, 133.84, 133.69, 132.00, 131.97, 129.69,
127.48, 127.41, 127.27, 125.03, 123.64, 121.04, 120.61, 120.48,
120.40, 119.40, 115.70, 112.10, 111.63, 111.00, 94.66, 93.74,
71.90, 64.61, 62.66, 57.24, 48.64, 45.57, 40.29, 39.49, 31.23, 28.39,
28.34, 18.96, 12.48. ESI-MS (m/z): calcd: 1122.3; found: 1123.9.
Anal. Calcd for C61H53F3N4O14: C, 65.24; H, 4.76; N, 4.99.
found: C, 65.24; H, 4.57; N, 4.76%.
Preparation of compound i-3
NaOH solution (47 mL, 5%, w/v) was injected into a 100 mL
2-neck flask and deaerated by bubbling with dry N2 for 30 min.
Then 3,5-dihydroxybenzoic acid (3.08 g, 20 mmol) was added
slowly into the reaction flask. After bubbling for 5 min, acryloyl
chloride (7.20 g, 80 mmol) in CH2Cl2 (10 mL) was added fol-
lowed by stirring for another 1 h. The white precipitate (4.90 g,
94%) was collected via filtration. 1H NMR (CDCl3, TMS,
d ppm): 7.81 (s, 2H), 7.33 (t, J ¼ 2.1 Hz, 1H), 6.69–6.63 (m, 2H),
6.39–6.29 (m, 2H), 6.10–6.06 (m, 2H). 13C NMR: 170.32, 163.85,
150.97, 133.57, 131.43, 127.31, 121.01, 120.87. ESI-MS (m/z):
calcd: 262.0; Found: 262.7.
Preparation of P1
A solution of freshly distilled methyl methacrylate (1.00 g, 10.0
mmol), 9-anthrylmethacrylate (i-14, 0.90 g, 3.27 mmol), and
AIBN (0.02 g, 0.12 mmol) in THF (6 mL) was degassed using the
freeze–pump–thaw procedure three times and filled with
nitrogen. The solution was first heated at 55 ꢁC for 2 h and then
at 62 ꢁC for 12 h. The viscous solution was poured into 100 mL of
methanol to precipitate the polymer. The crude polymer was
redissolved in THF and reprecipitated twice into methanol to
Preparation of compound i-12
In a similar manner described above for i-9, i-12 was synthesized
1
from i-11 as a red solid (1.04 g, 87%). H NMR (CDCl3, TMS,
d ppm): 10.10 (d, J ¼ 8.0 Hz, 1H), 7.79 (s, 4H), 7.43 (s, 1H), 7.31–
7.29 (m, 2H), 7.26 (d, J ¼ 14.0 Hz, 1H), 7.00 (d, J ¼ 16.0 Hz, 1H),
6.68–6.60 (m, 5H), 6.46 (d, J ¼ 8.0 Hz, 1H), 6.38–6.30 (m, 4H),
6.10–6.07 (m, 4H), 4.66 (t, J ¼ 4.5 Hz, 2H), 4.53–4.40 (overlap,
2H), 4.15 (t, J ¼ 7.0 Hz, 2H), 3.77–3.52 (overlap, 2H), 2.81 (m,
1H), 2.78 (s, 2H), 2.45 (s, 2H), 2.40 (s, 3H), 1.77 (m, 1H), 1.58 (t, J
¼ 13.0 Hz, 1H), 1.39 (s, 3H), 1.31 (d, J ¼ 6.5 Hz, 3H), 1.25 (s,
3H), 1.10 (s, 6H). 13C NMR: 190.83, 164.87, 163.86, 163.81,
153.70, 151.18, 150.98, 150.96, 150.93, 147.92, 145.20, 138.75,
135.88, 133.76, 133.63, 133.57, 133.52, 133.34, 133.34, 133.26,
132.15, 131.84, 130.65, 129.05, 127.48, 127.35, 127.33, 127.25,
126.34, 123.81, 123.64, 121.77, 120.94, 120.47, 120.44, 120.37,
120.31, 120.27, 117.62, 117.41, 113.22, 70.65, 64.66, 63.22, 54.80,
49.73, 46.48, 43.24, 43.00, 39.18, 38.98, 30.82, 29.70, 28.35, 28.29,
26.87, 24.76, 22.12, 20.76, 20.16, 20.05. ESI-MS (m/z): calcd:
955.3; found: 956.4.
1
obtain P1 (1.40 g, 79%). H NMR (300 MHz, CDCl3, TMS,
d ppm): 8.55–8.15 (br m), 8.10–7.80 (br s), 7.65–7.30 (br m), 6.20–
5.80 (br s), 3.70–3.10 (br m), 2.05–1.50 (br m), 1.15–0.50 (br m).
ꢁ
Tg ¼ 135 C. Molecular weight: Mn ¼ 37 000 Da with a poly-
dispersity of 2.43.
Preparation of i-15
A solution of N-(4-hydroxyphenyl)maleimide (1.00 g, 5.3 mmol),
a-methylstyrene (0.66 g, 5.6 mmol), and AIBN (0.01 g, 0.06
mmol) in THF (4 mL) was degassed using the freeze–pump–thaw
procedure three times and filled with nitrogen. The solution was
warmed to 65 ꢁC and kept stirring at that temperature for 12 h.
The resulting viscous solution was poured into methanol (100
mL) to precipitate the polymer. The polymer was redissolved in
THF and reprecipitated twice into methanol to obtain polymer
Preparation of chromophore C3
In a similar manner described above for C2, C3 was synthesized
from i-12 as a green solid (0.44 g, 74%). 1H NMR (CDCl3, TMS,
d ppm): 7.98 (dd, J ¼ 13.0 Hz, 1H), 7.79 (d, J ¼ 2.0 Hz, 1H), 7.71
(d, J ¼ 2.0 Hz, 1H), 7.55–7.48 (overlap, 5H), 7.32–7.27 (overlap,
3H), 7.16 (d, J ¼ 16.0 Hz, 1H), 6.76 (d, J ¼ 8.5 Hz, 1H), 6.68–6.60
(m, 4H), 6.38–6.27 (m, 4H), 6.11–6.07 (m, 4H), 4.69 (t, J ¼ 4.0
Hz, 2H), 4.54–4.39 (overlap, 2H), 4.16 (t, J ¼ 7.0 Hz, 2H), 3.79–
3.56 (overlap, 2H), 2.81 (m, 1H), 2.48 (s, 2H), 2.41 (s, 3H), 2.38–
2.24 (overlap, 2H), 1.80 (m, 1H), 1.58 (m, 1H), 1.40 (s, 3H), 1.31
(d, J ¼ 6.5 Hz, 3H), 1.24 (s, 3H), 1.05 (s, 3H), 0.99 (s, 3H). 13C
NMR: 164.65, 163.87, 163.68, 162.16, 151.07, 151.00, 150.93,
150.62, 146.43, 146.35, 138.61, 137.45, 133.78, 133.60, 133.55,
1
i-15 (1.10 g, 70%). H NMR (300 MHz, acetone, TMS, d ppm):
8.85–8.65 (br s), 7.60–7.05 (br m), 7.00–6.65 (br m), 6.20–5.80 (br
s), 3.70–3.10 (br m), 2.05–0.50 (br m), 1.15–0.50 (br m). Tg ¼ 237
ꢁC. Molecular weight: Mn ¼ 18 500 with a polydispersity of 2.29.
Preparation of P2 via postfunctionalization
To a mixture of polymer i-15 (0.19 g, hydroxyphenyl groups ¼
0.6 mmol) and 3-(anthracen-10-yl)propanoic acid (i-16, 0.30 g,
1.2 mmol) in 5 mL of dry pyridine, was added dropwise DIPC
(0.18 g, 1.15 mmol). The solution was stirred overnight. Then the
958 | J. Mater. Chem., 2012, 22, 951–959
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7 (a) D. M. Burland, R. D. Miller and C. A. Walsh, Chem. Rev., 1994,
94, 31; (b) T. J. Marks and M. A. Ratner, Angew. Chem., Int. Ed.
Engl., 1995, 34, 155; (c) R. D. Miller, D. M. Burland, M. Jurich,
V. Y. Lee, C. R. Moylan, J. I. Thackara, R. J. Twieg, T. Verbiest
and W. Volksen, Macromolecules, 1995, 28, 4970; (d) S. R. Marder,
B. Kippeien, A. K.-Y. Jen and N. Peyghambarian, Nature, 1997,
388, 845.
8 (a) H. Saadeh, D. Yu, L. M. Wang and L. P. Yu, J. Mater. Chem.,
1999, 9, 1865; (b) N. Song, L. Men, J. Gao, Y. Bai, G. Yu,
A. Beaudin and Z.-Y. Wang, Chem. Mater., 2004, 16, 3708; (c)
T.-A. Chen, A. K.-Y. Jen and Y. Cai, J. Am. Chem. Soc., 1995,
117, 7295; (d) Y. Enami, D. Mathine, C. T. Derose,
R. A. Norwood, J. Luo, A. K.-Y. Jen and N. Peyghambarian, Appl.
Phys. Lett., 2007, 91, 093505.
resulting polymer was poured into a large excess of methanol and
separated by filtration. The pure polymer P2 was obtained by
another precipitation in methanol twice (0.26 g, 81%, degree of
1
phenol termination: 100% by IR). H NMR (300 MHz, CDCl3,
TMS, d ppm): 8.43 (s, 1H), 8.13 (d, 2H), 7.71 (d, 2H), 7.25–6.74
(br m), 3.70–3.06 (br m), 2.05–1.50 (br m), 1.15–0.50 (br m). Tg ¼
215 ꢁC. Molecular weight: Mn ¼ 25 000 with a polydispersity of
2.20.
Acknowledgements
9 (a) For recent reviews: J. Luo, X.-H. Zhou and A. K.-Y. Jen, J. Mater.
Chem., 2009, 19, 7410; (b) P. Sullivan and L. Dalton, Acc. Chem. Res.,
2010, 43, 10; (c) L. Dalton, P. Sullivan and D. H. Bale, Chem. Rev.,
2010, 110, 25.
10 (a) Z. Shi, J. Luo, S. Huang, X.-H. Zhou, T.-D. Kim, Y.-J. Cheng,
B. Polishak, T. R. Younkin, B. A. Block and A. K.-Y. Jen, Chem.
Mater., 2008, 20, 6372; (b) Z. Shi, W. Liang, J. Luo, S. Huang,
B. Polishak, X. Li, T. R. Younkin, B. A. Block and A. K.-Y. Jen,
Chem. Mater., 2010, 22, 5601.
Financial support from Intel Corporation, National Science
Foundation (NSF-STC Program under Agreement Number
DMR-0120967),
acknowledged.
and
Boeing-Johnson
Foundation
is
Notes and references
11 F. Kajzar and J. M. Nunzi, Molecular Orientation Techniques, in
Beam Shaping Control with Nonlinear Optics, ed. F. Kajzar and R.
Reinisch, Plenum Press, New York, 1998, p. 101.
12 S. Liu, M. Haller, H. Ma, L. Dalton, S.-H. Jang and A. K.-Y. Jen,
Adv. Mater., 2003, 15, 603.
13 (a) J. Luo, H. Ma, M. Haller, A. K.-Y. Jen and R. R. Barto, Chem.
Commun., 2002, 888; (b) T.-D. Kim, J. Luo, Y. Tian, J.-W. Ka,
N. Tucker, M. Haller, J.-W. Kang and A. K.-Y. Jen,
Macromolecules, 2006, 39, 1676; (c) Y. Liao, C. Anderson,
P. Sullivan, A. Akelaitis, B. Robinson and L. R. Dalton, Chem.
Mater., 2006, 18, 1062.
1 (a) D. A. B. Miller, IEEE J. Sel. Top. Quantum Electron., 2000, 6,
1312; (b) Q. Xu, B. Schmidt, S. Pradhan and M. Lipson, Nature,
2005, 435, 325; (c) P. Dong, S. Liao, D. Feng, H. Liang, D. Zheng,
R. Shafiiha, C.-C. Kung, W. Qian, G. Li, X. Zheng,
A. Krishnamoorthy and M. Asghari, Opt. Express, 2009, 17, 22484;
(d) G. T. Reed, G. Mashanovich, F. Y. Gardes and D. J. Thomson,
Nat. Photonics, 2010, 4, 518.
2 (a) D. W. Zheng, D. Z. Feng, G. Gutierrez and T. Smith, Proc. SPIE–
Int. Soc. Opt. Eng., 2006, 6125, 61250E1; (b) W. M. Green,
M. J. Rooks, L. Sekaric and Y. A. Vlasov, Opt. Express, 2007, 15,
17106.
14 (a) J. Luo, S. Huang, Y.-J. Cheng, T.-D. Kim, Z. Shi, X.-H. Zhou and
A. K.-Y. Jen, Org. Lett., 2007, 9, 4471; (b) C. Zhang, L. R. Dalton,
M.-C. Oh, H. Zhang and W. H. Steier, Chem. Mater., 2001, 13, 3043.
15 Z. Shi, J. Luo, S. Huang, Y.-J. Cheng, T.-D. Kim, B. Polishak,
X.-H. Zhou, Y. Tian, S.-H. Jang, D. B. Knorr, Jr, R. M. Overney,
T. R. Younkin and A. K.-Y. Jen, Macromolecules, 2009, 42, 2438.
16 H. Wang, Z. Lu, S. J. Lord, K. A. Willets, J. A. Bertke, S. D. Bunge,
W. E. Moerner and R. J. Twieg, Tetrahedron, 2007, 63, 103.
17 A. Bacher, I. Bleyl, C. H. Erdelen, D. Haarer, W. Paulus and
H.-W. Schmidt, Adv. Mater., 1997, 9, 1031.
3 (a) L. Liao, A. Liu, D. Rubin, J. Basak, Y. Chetrit, H. Nyuyen,
R. Cohen, N. Izhaky and M. Paniccia, Electron. Lett., 2007, 43,
1196–1197; (b) C. Gunn, IEEE Micro, 2006, 26, 58.
4 (a) E. Mohammed, A. Alduino, T. Thomas, H. Braunisch, D. Lu,
J. Heck, A. Liu, I. Young, B. Barnett, G. Vandentop and
R. Mooney, Intel Technol. J., 2004, 8, 115; (b) M. J. Kobrinsky,
J. F. Zheng, B. C. Barnett, E. Mohammed, M. Reshotko,
F. Roberston, S. List, I. Young and K. Cadien, Intel Technol. J.,
2004, 8, 129.
5 I. A. Young, E. Mohammed, J. T. S. Liao, A. M. Kern, S. Palermo,
B. A. Block, M. R. Reshotko and P. L. D. Chang, IEEE J. Solid-State
Circuits, 2010, 45, 235.
6 B. A. Block, T. R. Younkin, P. S. Davids, M. R. Reshotko, P. Chang,
B. Polishak, S. Huang, J. Luo and A. K.-Y. Jen, Opt. Express, 2008,
16, 18326, and references therein.
18 C. A. Zuniga, S. Barlow and S. R. Marder, Chem. Mater., 2011, 23, 658.
19 M. Sprave, R. Blum and M. Eric, Appl. Phys. Lett., 1996, 69, 2962.
20 S. Huang, T. D. Kim, J. Luo, S. Hau, Z. Shi, X.-H. Zhou, H. L. Yip
and A. K.-Y. Jen, Appl. Phys. Lett., 2010, 96, 243311.
21 C. C. Teng and H. T. Man, Appl. Phys. Lett., 1990, 56, 1734.
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J. Mater. Chem., 2012, 22, 951–959 | 959