Synthesis of photochromic diarylethene polymers for a write-by-light/erase-by-heat recording system

Article abstract of DOI:10.1016/j.tet.2008.05.088

A functionalized styrene monomer (1a) having a photochromic diarylethene chromophore with functional properties of photocoloration, photostability of the colored state, and thermal erasion by heating was synthesized, and the polymer and copolymers of 1a were prepared by radical polymerization and copolymerization. Their polymers exhibited excellent photocoloration and rapid thermal bleaching above 150 °C in solution and in the solid state as well as the performance of the monomeric diarylethene chromophore. In addition, the colored state has a high photostability under visible room light. The diarylethene homopolymer had a glass transition temperature (T_g) as high as polystyrene. The copolymer of 1a with N-1-adamantylmaleimide exhibited extremely high T_g above 200 °C with keeping the photofunctional performance. Such photochromic polymer and copolymers with high T_g can be potentially applied to rewritable display materials and image recordings by a write-by-light/erase-by-heat system.

Full text of DOI:10.1016/j.tet.2008.05.088

Tetrahedron 64 (2008) 7611–7618
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Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Synthesis of photochromic diarylethene polymers for a write-by-
light/erase-by-heat recording system
,
b
,
a
Seiya Kobatake a , Itsuka Yamashita
*
a Department of Applied Chemistry, Graduate School of Engineering, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
b Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency (JST), Kawaguchi Center Building,
4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
A functionalized styrene monomer (1a) having a photochromic diarylethene chromophore with func-
tional properties of photocoloration, photostability of the colored state, and thermal erasion by heating
was synthesized, and the polymer and copolymers of 1a were prepared by radical polymerization and
copolymerization. Their polymers exhibited excellent photocoloration and rapid thermal bleaching
above 150 ꢀC in solution and in the solid state as well as the performance of the monomeric diarylethene
chromophore. In addition, the colored state has a high photostability under visible room light. The di-
arylethene homopolymer had a glass transition temperature (Tg) as high as polystyrene. The copolymer
of 1a with N-1-adamantylmaleimide exhibited extremely high Tg above 200 ꢀC with keeping the pho-
tofunctional performance. Such photochromic polymer and copolymers with high Tg can be potentially
applied to rewritable display materials and image recordings by a write-by-light/erase-by-heat system.
Ó 2008 Elsevier Ltd. All rights reserved.
Received 30 April 2008
Accepted 18 May 2008
Available online 23 May 2008
Keywords:
Photochromism
Diarylethene
Photochromic polymer
Thermal bleaching reaction
1. Introduction
application, diarylethene molecules having very low photo-
decoloration quantum yields and thermal stability at room temper-
Photochromic compounds undergo a photo-induced reversible
isomerization process between two isomers with different absorp-
tion spectra upon irradiation with light of appropriate wavelength.1,2
Theyexhibitdifferentchemicalandphysicalpropertychangessuchas
their absorption spectra, refractive indices, dielectric constants, oxi-
dation–reduction potentials, and geometrical structures because of
their molecular structural changes. They are classified into two types,
P-type (thermally stable of the photogenerated isomer) and T-type
(thermally unstable of the photogenerated isomer).1 Among various
photochromic compounds, diarylethenes with heterocyclic aryl rings
have been developed asa P-type photochromiccompound because of
some excellent characteristics such as thermal stability of both iso-
mers and fatigue-resistant property.3,4 Such materials can be poten-
tially used for application to optical memory media,5,6 switching
devices,7,8 display materials,9,10 and photo-mechanical actuators.11,12
When the photochromic materials are applied to image re-
cordings such as rewritable papers, the colored state should be stable
under room light. The photogenerated colored isomer of a typical
diarylethene derivative, 1,2-bis(2-methyl-5-phenyl-3-thienyl)per-
fluorocyclopentene, is stable for more than 1900 years at 30 ꢀC in the
dark.13,14 However, the colored isomer returns to the initial colorless
isomer under room light even at room temperature. For the recording
aturehavebeendeveloped.15,16 Thephotodecolorationquantumyield
is strongly suppressed by the introduction of methoxy groups at the
reactive 2- and 20-positions of the thiophene rings.15 Furthermore, for
the reusability of the materials, the colored isomers can return to the
colorless isomers thermally at high temperature above 100 ꢀC by the
introduction of the cyclohexyloxy groups at the 2- and 20-positions.16
From the viewpoint of the application in the thin film, we have
designed and synthesized novel photochromic polymers, in which
the photogenerated colored forms are stable under visible light and
return to the initial forms at temperature above 100 ꢀC though the
colored isomers are stable even at room temperature (Scheme 1). In
the present work, such polymer and copolymers including the
diarylethene chromophores in a high content were synthesized by
radical polymerization, and the chemical and physical properties of
the polymers, such as photoreactivity, photostability, thermal
bleaching reactivity, and thermal analysis, were examined in the
neat film as well as in solution.
2. Results and discussion
2.1. Synthesis of diarylethene polymers and their
characterization
Radical polymerization of 1a was carried out using an azoini-
tiator (AIBN) at 60 ꢀC under the condition shown in Table 1. After
* Corresponding author. Tel./fax: þ81 6 6605 2797.
E-mail address: kobatake@a-chem.eng.osaka-cu.ac.jp (S. Kobatake).
0040-4020/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2008.05.088

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S. Kobatake, I. Yamashita / Tetrahedron 64 (2008) 7611–7618
Scheme 1. Synthesis and photochromic reaction of poly(1a).
Table 1
Polymerization and copolymerization of 1a in toluene at 60 ꢀC and physical properties of the resulting polymers
[1a] (mol dmꢁ3
)
[3] (mol dmꢁ3
)
[4] (mol dmꢁ3
)
[AIBN] (mol dmꢁ3
)
Time (h) Yield (%) Content of 1a
in copolymer (mol %)
Mn (GPC) Mw/Mn (GPC) Tg (ꢀC) Tinit (ꢀC)
a
b
0.36
0.18
0.11
0.24
0
0
0
0
0
0
0
0.18
0.18
0.019
0.019
0.0050
0.019
0.019
0.020
0.010
10
5
9
4
4
58
65
57
56
59
83
74
100
21,000
29,000
67,000
24,000
15,000
20,000
36,000
1.85
1.94
2.20
2.04
2.26
2.46
2.39
104
122
125
130
234
d
0.18
0.25
0.36
0.41
0
61
49
42
0
46
49
d
d
>200c
>230c
>230c
d
0.18
0.18
10
10
240
238
0
a
Glass transition temperature determined by DSC (10 ꢀC minꢁ1).
b
c
Initial decomposition temperature determined by TGA (10 ꢀC minꢁ1).
Not detected below decomposition temperature.
polymerization for 10 h, the diarylethene polymer was obtained in
58% yield. The resulting polymer had an Mn of 21,000 and an Mw/Mn
of 1.85. The polydispersity of 1.5–2.0 indicates that the polymeri-
zation proceeded by a typical radical polymerization without any
significant side reaction. The thermal properties of the polymer
were evaluated using a differential scanning calorimetry (DSC) and
a thermogravimetric analysis (TGA). Figure 1 shows DSC and TGA
curves of the polymer. The polymer exhibited a Tg of 104 ꢀC, a Tinit of
234 ꢀC, and a Tmax of 300 ꢀC. A diarylethene polymer with the
methyl groups instead of the cyclohexyloxy groups has a Tg of
107 ꢀC.17 Any significant decomposition of poly(1a) below 200 ꢀC
was not observed. The introduction of the cyclohexyl groups in the
monomer and polymer was not affected to radical polymerization
and the thermal properties, respectively.
If such functionalized polymer materials are used for application
to image recordings according to the write-by-light/erase-by-heat
system, they are required to have a higher Tg than 160 ꢀC and the
performance should be maintained even at that temperature. Co-
polymers of styrene with 1-adamantyl methacrylate (3) exhibit
characteristics of high Tg. Tg of the copolymer increases with in-
creasing the content of 3. For example, the copolymer in the
composition ratio of 1:1 has a Tg of 166 ꢀC.18 On the other hand,
copolymers of styrene with N-1-adamantylmaleimide (4) gave the
alternate copolymer.19 The alternate copolymer exhibits Tg above
200 ꢀC. If the diarylethene monomer (1a) is copolymerized with 3
or 4, the resulting polymers may exhibit a higher Tg value than that
of the homopolymer of 1a.
In order to obtain high Tg diarylethene polymers, the co-
polymerization of 1a and 3 was done in the content of 50, 60, and
69 mol % in the feed of 3 (Scheme 2). The resulting copolymers had
a higher Mn than that of homopolymer of 1a. Table 1 shows a Tg of
the copolymers of 1a with 3. The Tg value increased with increasing
the content of 3 in the copolymer. However, Tg increased only up to
130 ꢀC even including 69 mol % of 3.
Figure 1. DSC trace (a) and TGA curve (b) of poly(1a).

S. Kobatake, I. Yamashita / Tetrahedron 64 (2008) 7611–7618
7613
Scheme 2. Photochromic reactions of poly(1a-co-3) and poly(1a-co-4).
The copolymerization of 1a with 4 was done aiming at the im-
provement of high Tg polymer. No significant endothermic peak
was observed below 200 ꢀC, as shown in Figure 2. It means that
poly(1a-co-4) exhibits much higher Tg value than 240 ꢀC.
film, the decrease in the population of the photoactive conforma-
tions of diarylethene moieties may result in the smaller photo-
cyclization quantum yield.22
2.3. Photostability and thermal stability of the colored form
2.2. Photochromism of diarylethene polymer
Poly(1b) was thermally stable at room temperature and also
stable under visible light. The photostability is due to the in-
troduction of alkoxy groups at the 2- and 20-positions. A diaryl-
ethene polymer (poly(2a)) having the methyl groups instead of the
cyclohexyloxy groups has photoreversibility between open- and
closed-ring form (Scheme 3).17 The introduction of the cyclo-
hexyloxy groups results in small photocycloreversion quantum
yield by a factor of ca. 20. Figure 5 shows a photostability of the
colored state. Poly(1b) and poly(1b-co-4) were very stable to visible
light in toluene, whereas poly(2b) was bleached with a faster rate.
Such photostability of the colored state can be maintained even in
the polymer film as well as in solution.
When the colored state of poly(1b) is heated at high tempera-
ture above 100 ꢀC, it is expected to return to the colorless state to
give poly(1a). The thermal decoloration reaction in the film was
followed by the absorbance changes of the closed-ring forms.
Figure 6a shows decay curves of thermal bleaching reactions of the
closed-ring forms in the film of poly(1b). The color disappeared
completely within 10 min at 150 ꢀC to reproduce poly(1a). The
photocoloration and thermal decoloration cycles can be repeated.
The thermal bleaching reaction was followed by a first-order ki-
netics as shown in Figure 6b. The slope of the first-order kinetic
plots corresponds to the rate constant of the reaction. The rate
constants were obtained as shown in Table 2. The thermal
Upon irradiation with ultraviolet (UV) light, the toluene solution
of poly(1a) turned blue and the colored state was thermally and
photochemically stable. Figure 3 shows UV–vis absorption spectral
changes upon irradiation with 313-nm light. Upon irradiation with
UV light the new absorption band of the closed-ring form appeared
at 650 nm. The conversion to the closed-ring form was determined
to be 92% by the 1H NMR and UV–vis absorption spectroscopic
analyses, as shown in Figure 4.
On the other hand, the photochromism in the film on a quartz
glass reached to 60% conversion at a photostationary state. The
photocyclization reaction rate at the early stage in the film was
smaller than that in toluene. In order to evaluate the photo-
reactivity, the photocyclization quantum yields were examined in
toluene and in the film. The quantum yield in toluene was de-
termined to be 0.40. It was similar to that of the low molecular
weight diarylethene molecule, 1,2-bis(2-cyclohexyloxy-5-phenyl-
3-thienyl)perfluorocylopentene, 0.43.16 On the other hand, the
quantum yield of the polymer in the film was determined to be
0.26, which was considerably smaller than that in toluene. Diaryl-
ethene molecules are fixed in some conformations in the solid-
state film because of the presence of bulky substituents such as the
cyclohexyloxy groups. Some of the conformations are photo-
chemically inactive.20,21 Therefore, in the case of the solid-state

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S. Kobatake, I. Yamashita / Tetrahedron 64 (2008) 7611–7618
Figure 2. DSC trace (a) and TGA curve (b) of poly(1a-co-4).
decoloration reaction rates of poly(1b) were similar to that of the
monomeric diarylethene.16 The activation energy (Ea) and the fre-
quency factor (A) of the decoloration reaction were determined
from the linear relation of the temperature dependence of the rate
Figure 3. Absorption spectral changes of poly(1a in toluene (a) and in the film (b)
upon irradiation with 313-nm light).
3. Conclusion
constants to be 125 kJ molꢁ1 and 2.0ꢂ1013
s
ꢁ1, respectively, as
We synthesized functionalized polymer and copolymers having
photochromic diarylethene chromophores with functional prop-
erties of photocoloration, photostability of the colored state, and
shown in Figure 7. The values are identical with those of the mo-
nomeric diarylethene in solution: Ea¼120 kJ molꢁ1, A¼4.4ꢂ1012 sꢁ1
.
The half-life times of the thermal cycloreversion reactions for
the closed-ring form at 170 and 25 ꢀC were estimated from the
extrapolation of the linear relation to be 19 s and 8.7 years, re-
spectively. The similar values to the monomeric diarylethene in
decalin indicate that the introduction of the diarylethene chro-
mophore to the polymer in the side chain functioned without any
loss of the performance. The polymer has very rapid thermal
cycloreversion rate at high temperature and high thermal stability
at room temperature. The temperature dependence of the thermal
cycloreversion reaction of poly(1b-co-4) is also shown in Figure 7.
The performance of poly(1b-co-4) was maintained without any loss
of the reactivity.
2.4. Application
The copolymer of 1a with 4 satisfies requirements of photo-
stability, thermally rapid reversibility at 170 ꢀC, and higher Tg above
200 ꢀC. The writing by UV light irradiation and erasing by heat in
the poly(1a-co-4) film were accomplished below Tg of the polymer.
Figure 8 shows image recordings of the poly(1a-co-4) by UV light
irradiation in photowriting and erasion by heating at 140 ꢀC. When
the colorless film was irradiated with 365-nm light using a photo-
mask, the colored pattern was observed. The pattern was stable for
more than 1 day under visible light and was bleached by heating.
Figure 4. Time-conversion curves for the photocyclization reactions of poly(1a) in
toluene (C) and in the film (B) upon irradiation with 313-nm light.

S. Kobatake, I. Yamashita / Tetrahedron 64 (2008) 7611–7618
7615
Scheme 3. Photochromic reaction of poly(2a).
Figure 5. Photostability of poly(1b) (C), poly(1b-co-4) (B), and poly(2b) (-) in tol-
uene upon irradiation with visible light.
Figure 6. Decay curves (a) and first-order kinetic plots (b) for thermal cycloreversion
reactions of poly(1b) in the neat film.
thermal erasion by heating. Their polymers exhibited excellent
photocoloration and rapid thermal bleaching above 150 ꢀC. The
colored state has a high photostability under visible room light. The
copolymer with N-1-adamantylmaleimide exhibited extremely
high Tg above 200 ꢀC with keeping the photofunctional perfor-
mance. Such photochromic polymer and copolymers with high Tg
can be potentially applied to rewritable display materials and im-
age recordings by a write-by-light/erase-by-heat system.
Table 2
Rate constant (k) and half-life time (t1/2) of thermal cycloreversion reaction of
poly(1b) and poly(1b-co-4) in the film
Temperature (ꢀC)
Poly(1b)
k (sꢁ1
Poly(1b-co-4)
)
t1/2 (min)
k (sꢁ1
)
t1/2 (min)
90
2.2ꢂ10ꢁ5
7.0ꢂ10ꢁ5
1.9ꢂ10ꢁ4
5.0ꢂ10ꢁ4
1.2ꢂ10ꢁ3
3.1ꢂ10ꢁ3
7.4ꢂ10ꢁ3
1.9ꢂ10ꢁ2
530
170
61
d
d
d
100
110
120
130
140
150
160
4. Experimental section
4.1. General
23
3.8ꢂ10ꢁ4
1.0ꢂ10ꢁ3
2.7ꢂ10ꢁ3
6.7ꢂ10ꢁ3
1.8ꢂ10ꢁ2
30
12
4.3
1.7
0.64
9.6
3.7
1.6
0.61
Solvents used were spectroscopic grade and purified by distil-
lation. 1H NMR spectra were recorded on a Jeol A-400 NMR spec-
trometer at 400 MHz. Initial temperature of degradation (Tinit) and
maximum degradation rate temperature (Tmax) of the polymers
were determined by a thermogravimetric analysis (TGA). TGA was
carried out using a Seiko TG/DTA-6200 and a polymer sample was
heated in a nitrogen stream at a heating rate of 10 ꢀC minꢁ1. Glass
transition temperature (Tg) was determined from an initial in-
flection point of temperature dependence on a differential scanning
calorimetry (DSC). DSC was run using a Seiko DSC-6200 at a heating
rate of 10 ꢀC minꢁ1. Absorption spectra in a solution were per-
formed with a JASCO V-560 spectrophotometer. A high-tempera-
ture chamber was used to maintain constant temperature of an
absorption quartz cell in a solution. Absorption spectra of the
polymer film were measured using a microscope connected with
a Hamamatsu PMA-11 photodetector. A hot stage (Mettler-Toledo
FP90/FP82) was used to maintain constant temperature of the
polymer film. Photoirradiation was carried out using a 200 W
mercury–xenon lamp (Moritex MUV-202) as the light source.
Monochromic light was obtained by passing the light through
a monochromator and a UV filter. The relative quantum yields were
determined by comparing the reaction yield with a reference
sample. The films were prepared by casting the toluene solution of
the polymers on the quartz glass substrate.

7616
S. Kobatake, I. Yamashita / Tetrahedron 64 (2008) 7611–7618
p-toluenesulfonic acid was refluxed using a Dean–Stark condenser
for 2.5 h by heating an oil bath at 150 ꢀC. The reaction mixture was
neutralized by a sodium hydrogen carbonate solution. The product
was extracted with ether. The organic layer was dried over MgSO4,
filtered, and concentrated. The residue was purified by re-
crystallization from hexane to give 0.40 g of 7 in 78% yield. 1H NMR
(400 MHz, CDCl3):
6.98 (s, 1H), 7.45–7.47 (m, 4H).
d
¼1.3–2.1 (m, 10H), 4.0–4.2 (m, 5H), 5.81 (s, 1H),
4.2.3. 1-(2-Cyclohexyloxy-5-phenyl-3-thienyl)-
heptafluorocyclopentene (8)
To 25 mL of dry THF solution containing 3-bromo-2-cyclo-
hexyloxy-5-phenylthiophene16 (0.39 g, 1.2 mmol) was added 1.6 M
n-BuLi solution in hexane (0.87 mL, 1.4 mmol) at ꢁ78 ꢀC under ar-
gon atmosphere, and the solution was stirred for 1.5 h at that low
temperature. Octafluorocyclopentene (0.27 mL, 1.9 mmol, Nippon
Zeon) was added to the reaction mixture at ꢁ78 ꢀC, and the mixture
was stirred for 1.5 h at that temperature. The reaction was stopped
by the addition of water. The product was extracted with ether. The
organic layer was dried over MgSO4, filtered, and concentrated. The
residue was purified by silica gel column chromatography using
hexane as the eluent to give 0.42 g of 8 in 81% yield. 1H NMR
Figure 7. Temperature dependence of thermal cycloreversion reaction rate constants
of poly(1b) in the film (C) and poly(1b-co-4) in the film (B).
4.2. Diarylethene monomer (1a)
(400 MHz, CDCl3):
d
¼1.3–2.1 (m, 10H), 4.28 (sep, J¼4 Hz, 1H), 7.15
(s, 1H), 7.25–7.50 (m, 5H); MS (FAB) m/z (Mþ) 450.
Compound 1a was prepared according to the synthetic routes as
shown in Scheme 4.
4.2.4. 1-(2-Cyclohexyloxy-5-phenyl-3-thienyl)-2-{2-cyclohexyloxy-
5-[4-([1,3]-dioxolanyl)-phenyl]-3-thienyl}perfluorocyclopentene (9)
To 5 mL of dry THF solution containing 7 (1.5 g, 3.7 mmol) was
added 1.6 M n-BuLi solution in hexane (2.5 mL, 4.0 mmol) at ꢁ78 ꢀC
under argon atmosphere, and the solution was stirred for 1.5 h at
that low temperature. Compound 8 (1.0 g; 2.2 mmol) in dry THF
(5 mL) was slowly added to the reaction mixture at ꢁ78 ꢀC, and the
mixture was stirred for 6.5 h at that temperature. The reaction was
stopped by the addition of water. The product was extracted with
ether. The organic layer was dried over MgSO4, filtered, and con-
centrated. The residue was purified by silica gel column chroma-
tography using hexane/ethyl acetate (8:2) as the eluent to give
4.2.1. 4-(4-Bromo-5-cyclohexyloxythiophen-2-yl)benzaldehyde (6)
To 45 mL of dry THF containing 3,5-dibromo-2-cyclo-
hexyloxythiophene (5) (2.4 g, 7.0 mmol) was added 1.6 M n-BuLi
solution in hexane (4.5 mL, 7.5 mmol) at ꢁ78 ꢀC under argon at-
mosphere, and the solution was stirred for 1 h at the low temper-
ature. Tri-n-butyl borate (2.7 mL, 10 mmol) was slowly added to the
reaction mixture at ꢁ78 ꢀC, and the mixture was stirred for 1.5 h at
that temperature. After warming the solution up to room temper-
ature, 20 wt % Na2CO3 (aq) (16 mL), 4-bromobenzaldehyde (1.3 g,
7.0 mmol), and tetrakis(triphenylphosphine) palladium(0) (0.34 g,
0.29 mmol) were added to the reaction mixture. The mixture was
refluxed for 7.5 h at 70 ꢀC. The product was extracted with ether.
The organic layer was dried over MgSO4, filtered, and concentrated.
The residue was purified by silica gel column chromatography us-
ing hexane/ethyl acetate (9:1) as the eluent to give 1.5 g of 6 in 59%
0.84 g of 9 in 50% yield. 1H NMR (400 MHz, CDCl3):
d¼1.0–2.1 (m,
20H), 4.0–4.2 (m, 6H), 5.81 (s, 1H), 7.1–7.5 (m, 11H).
4.2.5. 1-[2-Cyclohexyloxy-5-(4-formylphenyl)-3-thienyl]-2-
yield. 1H NMR (400 MHz, CDCl3):
d
¼1.3–2.1 (m, 10H), 4.2 (sep,
(2-cyclohexyloxy-5-phenyl-3-thienyl)perfluorocyclopentene (10)
Compound 10 was prepared from 9 by refluxing in the presence
of pyridinium p-toluenesulfonate (0.18 g, 0.70 mmol) in acetone
(5 mL) for 2 h. The product was extracted with ether. The organic
layer was dried over MgSO4, filtered, and concentrated. The residue
was checked by 1H NMR and used for the following reaction
without further purification. Yield: 0.15 g (100%). Compound 10: 1H
J¼4 Hz, 1H), 7.15 (s, 1H), 7.6–7.9 (m, 4H), 10.0 (s, 1H).
4.2.2. 2-[4-(4-Bromo-5-cyclohexyloxythiophen-2-yl)-phenyl]-
[1,3]dioxolane (7)
A toluene solution (46 mL) of 6 (0.46 g, 1.3 mmol) and ethylene
glycol (0.85 g, 14 mmol) in the presence of a small amount of
Figure 8. Photopatterning of poly(1a-co-4) film using a photomask by UV light irradiation and thermal bleaching by heating for 3 min at 140 ꢀC.

S. Kobatake, I. Yamashita / Tetrahedron 64 (2008) 7611–7618
7617
Scheme 4. Synthetic route of photochromic diarylethene monomer 1a.
NMR (400 MHz, CDCl3):
7.1–7.9 (m, 11H), 10.0 (s, 1H).
d
¼1.0–2.1 (m, 20H), 4.05 (sep, J¼4 Hz, 2H),
aqueous sodium hydrogen carbonate solution, and the mixture
was extracted with ether. The organic layer was dried over
MgSO4. After removal of the solvent, the residue was purified
by column chromatography on silica gel using hexane/ethyl ac-
etate (8:2) as the eluent. Pure 1a was obtained by a further
purification with HPLC. Yield: 0.15 g (85%). Compound 1a: 1H
4.2.6. 1-{2-Cyclohexyloxy-5-[4-(hydroxymethyl)phenyl]-
3-thienyl}-2-(2-cyclohexyloxy-5-phenyl-3-thienyl)-
perfluorocyclopentene (11)
To a solution of 10 (0.15 g, 0.22 mmol) in ethanol (7 mL) was
NMR (400 MHz, CDCl3):
d
¼1.0–2.1 (m, 20H), 4.03 (sep, J¼4 Hz,
added slowly
a
solution of potassium borohydride (12 mg,
2H), 5.36 (s, 2H), 5.39 (d, J¼11 Hz, 1H), 5.86 (d, J¼18 Hz, 1H),
6.74 (dd, J¼11 and 18 Hz, 1H), 7.1–7.5 (m, 13H), 8.0–8.1 (m,
2H). HRMS (FAB) m/z¼848.2438; calcd for C47H42F6O4S2 m/z¼
848.2429 (Mþ).
0.22 mmol) in ethanol (1 mL) and water (1 mL). After stirring for
1 h at room temperature, the reaction mixture was extracted with
ether and the organic layer was dried over MgSO4. Removal of the
solvent gave alcohol 11. It was used for the following reaction
without any further purification. Yield: 0.15 g (98%). Compound 11:
1H NMR (400 MHz, CDCl3):
2H), 4.7 (s, 2H), 7.1–7.5 (m, 11H).
d
¼1.0–2.1 (m, 21H), 4.03 (sep, J¼4 Hz,
4.3. Polymerization
Polymerizations were run in glass tubes sealed off under vac-
uum. Monomer 1a was polymerized by a radical polymerization
using 2,20-azobisisobutyronitrile (AIBN) as an initiator in toluene at
60 ꢀC. After the polymerization, the polymer was obtained by
precipitation in methanol. Number- and weight-average molecular
weight (Mn and Mw) of the polymers was determined by gel-per-
meation chromatography (GPC) at 40 ꢀC in THF as the eluent. GPC
4.2.7. Monomer 1a
A
solution of 11 (0.15 g, 0.21 mmol), p-vinylbenzoic acid
(0.062 g, 0.42 mmol), dicyclohexylcarbodiimide (DCC) (0.094 g,
0.46 mmol), and 4-dimethylaminopyridine (DMAP) (0.028 g,
0.23 mmol) in dry THF (4.6 mL) was stirred under argon for 24 h
at room temperature. To the reaction mixture was added an

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was performed with a Tosoh 8000 series GPC system equipped with
TSK-gel columns.
Acknowledgements
This work was partly supported by a Grant-in-Aid for Scientific
Research (C) (No. 19550142) from the Ministry of Education, Cul-
ture, Sports, Science and Technology of Japan, and PRESTO, Japan
Science and Technology Agency.
13. Irie, M.; Lifka, T.; Uchida, K.; Kobatake, S.; Shindo, Y. Chem. Commun. 1999,
747–748.
14. Irie, M.; Lifka, T.; Kobatake, S.; Kato, N. J. Am. Chem. Soc. 2000, 122, 4871–
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