Synthesis and physical properties of poly(phenylene vinylene)s having oligo(ethylene oxide) in the side chain

Article abstract of DOI:10.1080/15421400490436214

Oligo(ethylene oxide) chains were introduced into the phenyl ring of the poly(phenylene vinylene) (PPV) derivatives to obtain electronic and ionic conductive liquid crystalline PPV derivatives. Thermal decomposition of all PPV derivatives occurred before isotropic melt. A typical texture of the liquid crystalline phase was not shown but birefringence was observed below the thermal decomposition temperature. Exhibition of a smectic phase for the polymers having triethylene or tetraethylene oxide chains was supported by X-ray measurements. Electronic conductivity of the PPV derivatives doped with I ₂ and ionic conductivity of the mixture of these polymers and LiClO₄ were also discussed.

Full text of DOI:10.1080/15421400490436214

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Synthesis and Physical
Properties of Poly(Phenylene
Vinylene)s having
Oligo(Ethylene Oxide) in the
Side Chain
Takashi Mihara a , Takahiro Yada a & Naoyuki Koide a
a Department of Chemistry, Science University of
Tokyo, Shinjuku-ku, Tokyo, Japan
Available online: 18 Oct 2010
To cite this article: Takashi Mihara, Takahiro Yada & Naoyuki Koide (2004): Synthesis
and Physical Properties of Poly(Phenylene Vinylene)s having Oligo(Ethylene Oxide) in
the Side Chain, Molecular Crystals and Liquid Crystals, 411:1, 421-437
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Mol. Cryst. Liq. Cryst., Vol. 411, pp. 421=[1463]–437=[1479], 2004
Copyright # Taylor & Francis Inc.
ISSN: 1542-1406 print=1563-5287 online
DOI: 10.1080=15421400490436214
SYNTHESIS AND PHYSICAL PROPERTIES OF
POLY(PHENYLENE VINYLENE)S HAVING
OLIGO(ETHYLENE OXIDE) IN THE SIDE CHAIN
Takashi Mihara, Takahiro Yada, and Naoyuki Koide
Department of Chemistry, Faculty of Science, Science University
of Tokyo, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan
Oligo(ethylene oxide) chains were introduced into the phenyl ring of the poly-
(phenylene vinylene) (PPV) derivatives to obtain electronic and ionic conduc-
tive liquid crystalline PPV derivatives. Thermal decomposition of all PPV
derivatives occurred before isotropic melt. A typical texture of the liquid crys-
talline phase was not shown but birefringence was observed below the thermal
decomposition temperature. Exhibition of a smectic phase for the polymers
having triethylene or tetraethylene oxide chains was supported by X-ray
measurements. Electronic conductivity of the PPV derivatives doped with I2
and ionic conductivity of the mixture of these polymers and LiClO4 were also
discussed.
Keywords: electronic conductivity; ionic conductivity; oligo(ethylene oxide); poly(phenylene
vinylene); smectic phase
INTRODUCTION
p-Conjugated polymers were extensively investigated because of their
various optical and electrical functions in their main chains. In general,
most p-conjugated polymers are insoluble in any solvents and infusible.
However, it is well-known that the introduction of the substituted group
to the side chain of the p-conjugated polymers increases solubility and
fusibility of the p-conjugated polymers [1–6].
The conductivity of the p-conjugated polymers is enhanced by
controlling the orientation of their polymer backbone. Stretching of the
p-conjugated polymer, polymerization under magnetic field or liquid crystal
field, etc are carried out to control the orientation of the polymer backbone
[7]. The liquid crystalline compound oriented under magnetic field has
Address correspondence to Naoyuki Koide, Department of Chemistry, Faculty of Science,
Science University of Tokyo, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan.
421=[1463]

422=[1464]
T. Mihara et al.
been used for the medium of the acetylene polymerization [8]. The electri-
cal conductivity of the obtained polyacetylene is about 104 Scmꢀ1.
On the basis of the improvement of the solubility for polythiophene with
the side chain [1–6] and the enhancement of the conductivity for the
oriented polyacetylene [8], it can be expected that the conductive liquid
crystalline polymers would improve their conductivity, solubility and fusi-
bility based upon the above two aspects. The conductive liquid crystalline
polymers were obtained by the introduction of the mesogenic group into
the side chain of the p-conjugated polymers. Oh et al. reported that the
polyacetylene with a mesogenic group in the side chain itself displays
mesomorphic properties [9].
PPV is one of the p-conjugated polymers and is noticed as an optically
functional material [10–15]. The backbone of PPV is consisted of phenyl
rings and conjugated double bonds and the backbone is a rigid rod core.
Consequently, PPV itself would be a candidate of a mesogenic group. If a
flexible chain is introduced to the phenyl ring of PPV, the resultant PPV
derivatives would produce a liquid crystalline phase. The exhibition of
the liquid crystalline phase has the capability of the oriented polymer back-
bone of the PPV derivatives. The orientation of the polymer backbone
would improve optical and electrical properties of the PPV derivatives.
In this study, in order to obtain electronic and ionic conductive liquid
crystalline PPV derivatives, flexible oligo(ethylene oxide) (EO) chains
were introduced into the phenyl ring of the PPV derivatives, as shown in
Figure 1. Thermal, optical and electrical properties of the PPV derivatives
were investigated.
EXPERIMENTAL
Materials
Synthetic methods of PPV derivatives were summarized in Schemes 1 and 2,
respectively. Typical synthetic procedures were described below [10–15].
FIGURE 1 Chemical structures of PPV derivatives.

Synthesis and Physical Properties of Poly(Phenylene Vinylene)s 423=[1465]
SCHEME 1 Synthesis of mEO-PPV.
Tetraethylene glycol monomethyl ether
Potassium hydroxide (110 g, 1.67 mol) and tetraethylene glycol (325 g,
1.67mol) were dissolved in a mixed solvent of water (70 ml) and dioxane
(300ml). To the solution was added dimethylsulfate (70 g, 0.56 mol) dropwise
over 6 hours at 70ꢁC. The reaction mixture was stirred at 70ꢁC for 10hours. An
aqueous solution of HCl was added to the reaction mixture until the pH value
of the resultant mixture became about 7–8. After dioxane and water were
evaporated under reduced pressure, precipitate was removed by filtration.
The filtrate was extracted with chloroform. The chloroform was evaporated
under reduced pressure. The residue was purified by the fractional distillation
(1 mmHg, 105ꢁC). The product was obtained in a 42% yield (116 g).

424=[1466]
T. Mihara et al.
SCHEME 2 Synthesis of 2,5-mEO-PPV.
1H-NMR (CDCl3) d ppm: 3.38 (s, 3H, OCH3), 3.45–3.80 (m, 16H, OCH2).
2-[2-(2-Methoxyethoxy)ethoxy]Ethyl tosylate: Ts-3EO
Triethylene glycol monomethyl ether (123 g, 0.75 mol) was dissolved in
pyridine (200 ml). The pyridine solution was cooled to ꢀ10ꢁC. P-Toluene-
sulfonyl chloride (186 g, 0.975 mol) was added to the pyridine solution and
then the reaction mixture was stirred for 8 hours. Water was added to the
reaction mixture, and then an aqueous solution of HCl was added to the
mixture. The mixture was extracted with chloroform. The chloroform
solution was washed with water. The chloroform solution was dried over
magnesium sulfate. The chloroform was evaporated under reduced press-
ure. The residue was freeze-dried. The colorless and clear liquid was
obtained in 98% yield (233 g).
1H-NMR (CDCl3) d ppm: 2.44 (s, 3H, CH3), 3.40 (s, 3H, OCH3),
3.50–3.80 (m, 10H, OCH2), 4.16(t, 2H, OCH2), 7.36(d, 2H, Ar), 7.79(d, 2H, Ar).

Synthesis and Physical Properties of Poly(Phenylene Vinylene)s 425=[1467]
Ts-4EO and Ts-8EO
Ts-4EO and Ts-8EO were synthesized by the similar synthetic method
to Ts-3EO. Ts-4EO and Ts-8EO were obtained in 92% or 61% yield,
respectively.
Ts-4EO: 1H–NMR (CDCl3) d ppm: 2.50 (s, 3H, CH3), 3.44 (s, 3H, OCH3),
3.50–3.80 (m, 14H, OCH2), 4.16(t, 2H, OCH2), 7.35(d, 2H, Ar), 7.76
(d, 2H, Ar).
Ts-8EO: 1H-NMR (CDCl3) d ppm: 2.40 (s, 3H, CH3), 3.40 (s, 3H, OCH3),
3.50–3.80(m,30H,OCH2),4.20(t,2H,OCH2),7.36(d,2H,Ar),7.79(d,2H,Ar).
Methoxy-4-( triethoxymethoxy)benzene
p-Methoxyphenol (25 g, 0.2 mol) was dissolved in acetone (150 ml).
A potassium carbonate (83 g, 0.6 mol) was added to the acetone solution,
and then the mixture was refluxed for 1 hour. An acetone solution
(50 ml) of Ts-3EO (77 g, 0.24 mol) was added dropwise to the mixture.
After the reaction mixture was refluxed for 12 hours, the acetone was eva-
porated under reduced pressure. The residue was extracted with chloro-
form and the chloroform solution was washed with an aqueous solution
of potassium hydroxide. And then the chloroform solution was washed with
water. The chloroform solution was dried over magnesium sulfate.
The chloroform was evaporated under reduced pressure. The residue
was purified by column chromatography (eluent; ethyl acetate:
hexane ¼ 1:3). The colorless liquid was obtained in an 86% yield (46 g).
1H-NMR (CDCl3) d ppm: 3.44 (s, 3H, OCH3), 3.55 (s, 3H, OCH3), 3.6–3.9
(m, 10H, OCH2), 4.08 (t, 2H, OCH2), 6.8 (q, 4H, Ar).
Methoxy-4-(tetraethoxymethoxy)benzene and methoxy-4-
(octaethoxymethoxy)benzene
Methoxy-4-(tetraethoxymethoxy)benzene and methoxy-4-(octaethoxy-
methoxy)benzene were synthesized similarly. Methoxy-4-(tetraethoxy-
methoxy)benzene was obtained in a 71% yield (22.5 g). And then
methoxy-4-(octaethoxymethoxy)benzene was obtained in a 51% yield.
Methoxy-4-(tetraethoxymethoxy)benzene:1H-NMR (CDCl3) d ppm: 3.45
(s, 3H, OCH3), 3.57 (s, 3H, OCH3), 3.6–3.9 (m, 14H, OCH2), 4.00 (t, 2H,
OCH2), 6.8(q, 4H, Ar).
Methoxy-4-(octaethoxymethoxy)benzene: 1H–NMR (CDCl3) d ppm:
3.47 (s, 3H, OCH3), 3.56 (s, 3H, OCH3), 3.6–3.9 (m, 30H, OCH2), 4.00 (t,
2H, OCH2), 6.8(q, 4H, Ar).
1,4-bis(triethoxymethoxy)benzene
Hydroquinone (22 g, 0.2 mol) was dissolved in 2-methylethylketone
(MEK, 250 ml) and then potassium carbonate (110 g, 0.8 mol) was added

426=[1468]
T. Mihara et al.
to the MEK solution. The mixture was refluxed for 1 hour and then to the
mixture was added dropwise the MEK solution (50 ml) of Ts-3EO (160 g,
0.5 mol). After the reaction mixture was refluxed for 48 hours, MEK was
evaporated under reduced pressure. The residue was extracted with chloro-
form and the chloroform solution was washed with an aqueous solution of
potassium hydroxide and water. The chloroform solution was dried over mag-
nesium sulfate. After the chloroform was evaporated under reduced press-
ure, the residue was purified by column chromatography (eluent; acetone:
chloroform ¼ 1:15).Thecolorlessliquidwasobtainedina51%yield(23.5 g).
1H-NMR (CDCl3) d ppm: 3.40 (s, 6H, OCH3), 3.5–3.9 (m, 20H, OCH2),
4.10 (t, 4H, OCH2), 6.87( s, 4H, Ar).
1,4-Bis(tetraethoxymethoxy)benzene
1,4-Bis(tetraethoxymethoxy)benzene was synthesized similarly. This
compound was obtained in an 80% yield.
1H-NMR (CDCl3) d ppm: 3.40 (s, 6H, OCH3), 3.5–3.9 (m, 28H, OCH2),
4.12 (t, 4H, OCH2), 6.89(s, 4H, Ar).
1,4-Bis(chloromethyl)-2-methoxy-5-(triethoxymethoxy)-
benzene
Methoxy-4-(triethoxymethoxy)benzene (27 g, 0.1 mol) was dissolved in
dioxane (60 ml). An aqueous solution of formaldehyde (18 ml, 0.22 mol) and
an aqueous solution of hydrochloric acid (36 ml, 0.4 mol) were added to the
dioxane solution. An excess hydrochloric acid gas was bubbled into the
reaction mixture for 5 hours at room temperature. Furthermore after an
aqueous solution of formaldehyde (18 ml, 0,22 mol) was added to the reac-
tion mixture, an excess hydrochloric acid gas was bubbled into the reaction
mixture for 6 hours. An aqueous solution of sodium hydrogen carbonate was
added to the reaction mixture, and then the mixture was extracted with
chloroform. The chloroform solution was washed with water and dried over
magnesium sulfate. The chloroform was evaporated under reduced pressure.
The residue was purified by column chromatography (eluent; ethyl acetate:
hexane ¼ 1:2). The colorless liquid was obtained in a 73% yield (27 g).
1H-NMR (CDCl3) d ppm: 3.40 (s, 3H, OCH3), 3.5–3.7 (m, 8H, OCH2),
3.86(m, 5H, OCH2 and OCH3), 4.20(t, 2H, OCH2), 4.69(d, 4H, Cl-CH2),
6.91(s, 1H, Ar); 6.97(s, 1H, Ar).
IR (nujol) m-cmꢀ1: 1618 and 1510 (aromatic group), 1215 (Ar-O), 1107
(C-O-C), 849 (C-H, Ar), 729 (C-Cl).
1,4-Bis(chloromethyl)-2-methoxy-5-(tetraethoxymethoxy)-
benzene
1,4-Bis(chloromethyl)-2-methoxy-5-(tetraethoxymethoxy)benzene was
synthesized similarly. This compound was obtained in a 69% yield.

Synthesis and Physical Properties of Poly(Phenylene Vinylene)s 427=[1469]
1H-NMR (CDCl3) d ppm: 3.39 (s, 3H, OCH3), 3.5–3.7 (m, 12H, OCH2),
3.72 (s, 3H, OCH3), 3.86 (t, 2H, OCH2), 4.20(t, 2H, OCH2), 4.70(d, 4H,
Cl-CH2), 6.93(s, 1H, Ar), 6.97(s, 1H, Ar).
IR (nujol) m cm ꢀ 1: 1618 and 1510 (aromatic group), 1212 (Ar-O), 1112
(C-O-C), 849 (C-H, Ar), 734 (C-Cl).
1,4-Bis(chloromethyl)-2-methoxy-5-(octaethoxymethoxy)-
benzene
1,4-Bis(chloromethyl)-2-methoxy-5-(octaethoxymethoxy)benzene was
synthesized similarly and this compound was purified by recrystallization
from the mixed solvent (ethanol: hexane ¼ 1:3) after purification by
column chromatography (eluent; acetone: chloroform ¼ 1:15). This
compound was obtained in a 47% yield.
1H-NMR (CDCl3) d ppm: 3.39 (s, 3H, OCH3), 3.5–3.7 (m, 28H, OCH2),
3.89 (m, 5H, OCH2and OCH3 ), 4.22 (t, 2H, OCH2), 4.73 (d, 4H, Cl-CH2),
6.98(s, 2H, Ar).
IR (nujol) m cmꢀ1: 1597 and 1516 (aromatic group), 1208 (Ar-O), 1112
(C-O-C), 860 (C-H, Ar), 742 (C-Cl).
1,4-Bis(chloromethyl)-2-5-bis(triethoxymethoxy)benzene
This compound was prepared according to the synthetic method of 1,4-Bis
(chloromethyl)-2-methoxy-5-(triethoxymethoxy)benzene. This compound
was purified by column chromatography (eluent; acetone: chloroform ¼ 1:15).
Furthermore this compound was purified by recrystallization from the mixed
solvent of ethanol and hexane (ethanol : hexane ¼ 1:3). This compound was a
white solid and was obtained in a 59% yield (29.7 g).
1H–NMR (CDCl3) d ppm: 3.45 (s, 6H, OCH3), 3.5–3.7 (m, 20H, OCH2),
4.17 (m, 4H, OCH2), 4.68 (d, 4H, Cl-CH2), 6.90 (d, 2H, Ar).
IR (nujol) m cm ꢀ 1: 1601 and 1526 (aromatic group), 1218 (Ar-O), 1108
(C-O-C), 857 (C-H, Ar), 733 (C-Cl).
1,4-Bis(chloromethyl)-2-5-bis(tetraethoxymethoxy)benzene
1,4-Bis(chloromethyl)-2-5-bis(tetraethoxymethoxy)benzene was prepared
according to the synthetic method of 1,4-Bis(chloromethyl)-2-5-bis
(triethoxymethoxy)benzene. This compound was obtained in a 48% yield.
1H-NMR (CDCl3) d ppm: 3.47 (s, 6H, OCH3), 3.5–3.7 (m, 28H, OCH2),
4.16 (m, 4H, OCH2), 4.68 (d, 4H, Cl-CH2), 6.90 (d, 2H, Ar).
IR (nujol) m cm ꢀ 1: 1612 and 1521 (aromatic group), 1215 (Ar-O), 1114
(C-O-C), 857 (C-H, Ar), 742 (C-Cl).
Poly [2-methoxy-5-(triethoxymethoxy)-1,4-phenylene-
vinylene] : 3EO-PPV
tBuOK (4.2 g, 37.5 mmol) was added to dry tetrahydrofuran (THF,
150 ml) in a dry vessel. THF solution (70 ml) of 1,4-Bis(chloromethyl)-2-

428=[1470]
T. Mihara et al.
methoxy-5-(triethoxymethoxy)benzene (3.7 g) was added dropwise to the
THF solution over 2 hours. After the reaction mixture was stirred for 48
hours at room temperature, THF was evaporated under reduced pressure.
The residue was poured into water and then the precipitate was washed
with water. The polymer was purified with methanol using Soxhlet extrac-
tor. The residue was extracted with chloroform. The chloroform solution
was poured into methanol. The red solid was obtained in a 26% (0.75 g).
1H-NMR (CDCl3) d ppm: 3.42 (s, 6H, OCH3), 3.5–3.95 (m, 10H, OCH2),
4.25 (s, 2H, OCH2), 7.10 (d, 2H, vinyl), 7.49 (s, 2H, Ar).
Poly[2-methoxy-5-(tetraethoxymethoxy)-1,4-phenylene-
vinylene] : 4EO-PPV
Poly[2-methoxy-5-(tetraethoxymethoxy)-1,4-phenylenevinylene] was
prepared according to the synthetic method of poly[2-methoxy-5-(triethox-
ymethoxy)-1,4-phenylenevinylene]. This polymer was obtained in a 35%
yield (1.2 g).
1H-NMR (CDCl3) d ppm: 3.39 (s, 6H, OCH3), 3.5–3.85 (m, 14H, OCH2),
4.25 (s, 2H, OCH2), 7.13 (d, 2H, vinyl), 7.50 (s, 2H, Ar).
Poly[2-methoxy-5-(octaethoxymethoxy)-1,4-phenyleneviny-
lene] : 8EO-PPV
Poly[2-methoxy-5-(octaethoxymethoxy)-1,4-phenylenevinylene]
was
prepared according to the synthetic method of poly[2-methoxy-5-(triethox-
ymethoxy)-1,4-phenylenevinylene]. This polymer was obtained in a 47%
yield (2.4 g).
1H-NMR (CDCl3) d ppm: 3.37 (s, 3H, OCH3), 3.45–3.95 (m, 33H, OCH2
and OCH3), 4.21 (s, 2H, OCH2), 7.19 (d, 2H, vinyl), 7.45 (s, 2H, Ar).
Poly[2-5-(triethoxymethoxy)-1,4-phenylenevinylene] : -
2,5-3EO-PPV
Poly[2-5-(triethoxymethoxy)-1,4-phenylenevinylene] was prepared
according to the synthetic method of poly[2-methoxy-5-(triethoxy-
methoxy)-1,4-phenylenevinylene]. This polymer was obtained in a 19%
yield (0.82 g).
1H-NMR (CDCl3) d ppm: 3.40 (s, 6H, OCH3), 3.45–3.95 (m, 20H, OCH2),
4.19 (s, 4H, OCH2), 7.19 (d, 2H, vinyl), 7.38 (s, 2H, Ar).
Poly[2-5-(tetraethoxymethoxy)-1,4-phenylenevinylene] : -
2,5-4EO-PPV
Poly[2-5-(tetraethoxymethoxy)-1,4-phenylenevinylene] was prepared
according to the synthetic method of poly[2-methoxy-5-(triethoxy-
methoxy)-1,4-phenylenevinylene]. This polymer was obtained in a 12%
yield (0.64 g).

Synthesis and Physical Properties of Poly(Phenylene Vinylene)s 429=[1471]
1H-NMR (CDCl3) d ppm: 3.40 (s, 6H, OCH3), 3.45–3.95 (m, 28H, OCH2),
4.10 (s, 4H, OCH2), 7.14 (d, 2H, vinyl), 7.45(s, 2H, Ar).
Characterization
1H-NMR was carried out with a JEOL JNM-LA 500 spectrometer using
CDCl3 as the solvent. Infrared spectra were recorded on a JEOL JIR
7000 spectrometer. IR Spectra were collected at 4 cmꢀ1 resolution. DSC
measurements were conducted with
a
Mettler DSC821e. Optical
microscopy was performed on a Nikon polarizing optical microscope, OPTI-
PHOTO-POL, equipped with a Mettler FP80 controller and a FP82 hot
stage. Thermal properties of synthesized materials were investigated by
optical microscopy and DSC measurements. X-ray diffraction patterns were
recorded with a RIGAKU RINT 2500 series with Ni-filtered CuKa radiation.
The sample in quartz capillary (diameter 1 mm) was held in a temperature-
controlled cell (RIGAKU LC high-temperature controller). Gel permeation
chromatography (GPC) was carried out with a Tosoh HLC-8020 instrument
using chloroform as the eluent, equipped with four columns (TSK
gel G4000HHR, G3000HHR, G2000HHR and G2000HHR). The electrical con-
ductivity was measured with a Mitsubishikagaku Loresta HP (MCP-T410)
electrometer using four-probe (Mitsubishikagaku MCP-TP06P) technique.
The ionic conductivity of the mixtures was measured with a.c. impedan-
ce=gain-phase analyzer SI1260) over the frequency range 102–107Hz at
temperature ranges 30–160ꢁC. Sample temperature was controlled using
a Mettler FP80 controller and a FP82 hot stage. UV-vis spectroscopy mea-
surements were carried out with a HITACHI U-3410 spectrophotometer.
Fluorescence spectroscopy measurements were carried out with a HITA-
CHI F-4500 equipped with an optical fiber.
RESULTS AND DISCUSSION
The color of these PPV derivatives was red. These PPV derivatives were
soluble in organic solvents, such as CH2Cl2, CHCl3 and THF, etc. Thermal
properties of the PPV derivatives were investigated by polarized optical mi-
croscopy, and DSC measurements. Phase structures of the PPV derivatives
were examined by X-ray measurements. Thermal properties, molecular
weight and polydispersity for the PPV derivatives were summarized in
Table 1.
In DSC curves of all the PPV derivatives, both a remarkable glass tran-
sition and a peak cannot be detected. Thermal decomposition occurred
for all the PPV derivatives before they become the isotropic melt. However,
birefringence was observed for the PPV derivatives. We considered that

430=[1472]
T. Mihara et al.
TABLE 1 Thermal Properties of PPV Derivatives
Phase transition
temperatures=ꢁC
Number-average
molecular weight ðMnÞ
Polymers
Mw=Mn
270
M ꢀ! decomp:
235
3EO-PPV
4EO-PPV
5700
6200
2.6
3.6
1.9
4.5
5.4
250
M ꢀ! decomp:
8EO-PPV
2,5-3EO-PPV
2,5-4EO-PPV
M ꢀ! decomp:
215
9900
19000
11000
Sm ꢀ! decomp:
200
Sm ꢀ! decomp:
M; mesophase, Sm; smectic phase, decomp.; thermal decomposition.
glass transition temperatures of the PPV derivatives would be lower than
the starting temperature (ꢀ50ꢁC) in DSC measurements. The flexible side
chains of PPV derivatives would be in a liquid-like state. We could not
detect glass transition temperatures of these PPV derivatives by DSC
measurements.
X-ray measurements of the PPV derivatives were carried out to clarify
the phase structure of them. A small peak in the small-angle region and
a broad peak in the wide-angle region were observed for 3EO-PPV,
4EO-PPV and 8EO-PPV that have one oligo EO chain per benzene ring in
the polymer backbone. These X-ray patterns supported that these PPV
derivatives would exhibit some kinds of mesophases, however we could not
observe clear optical textures of these PPV derivatives. Therefore we
considered that these PPV derivatives exhibited a mesophase.
Figure 2 showed the X-ray patterns of 2,5-3EO-PPV. Similar X-ray
patterns were also observed for 2, 5-4EO-PPV. These PPV derivatives have
two oligo EO chains per benzene ring in the polymer backbone. A sharp
peak in the small-angle region and a broad peak in the wide-angle region
were observed in the X-ray patterns of 2, 5-3EO-PPV. These results indi-
cated that these PPV derivatives exhibited a layer structure like a smectic
phase. The d-spacing due to the sharp peak in the small-angle region was
˚
about 21 A for 2, 5-3EO-PPV, while the calculated length of side chain
˚
for 2,5-3EO-PPV was about 12 A. A possible mesomorphic structure model
of 2, 5-3EO-PPV was shown in Figure 2.
The mixtures of the poly(ethylene oxide) (PEO) derivatives and alkali
metal salts are intensively investigated for the ionic conductive material.
Furthermore new functional materials would be generated by combination
of ionic conductive properties and optical properties based upon p-
conjugated polymers. One of the new typical functional properties would
be the polymer light-emitting electrochemical cells (LEC) composed of
the mixture of PPV derivative, PEO and lithium trifluoromethanesulfonate

Synthesis and Physical Properties of Poly(Phenylene Vinylene)s 431=[1473]
FIGURE 2 X-ray patterns of 2,5-3EO-PPV.
[16]. We expect that ionic conductivity would be enhanced in the liquid
crystalline state in which ionic conductive path would be generated.
We prepared the various mixtures of LiClO4 and PPV derivatives. Glass
transition temperature of the mixtures was detected by DSC measure-
ments. Glass transition temperatures of the mixtures were determined
based on the shift of the baseline of DSC curves. Glass transition tempera-
tures increased with increasing fraction of LiClO4 in the mixtures as shown
in Table 2. Increase in glass transition temperatures would be based upon
the formation of the complex of lithium ion and oxygen atom in the
EO chain. In general, glass transition temperatures are related to the
TABLE 2 Thermal Properties of Mixtures of PPV Derivative and
LiClO4
Polymers (LiClO4)
Phase transition temperatures=ꢁC
?
235
8EO-PPV(4%)
8EO-PPV(7%)
g ꢀ! M ꢀ! decomp:
?
235
g ꢀ! M ꢀ! decomp:
ꢀ25
15
235
8EO-PPV(10%)
8EO-PPV(20%)
2,5-3EO-PPV(4%)
2,5-3EO-PPV(7%)
2,5-4EO-PPV(4%)
2,5-4EO-PPV(7%)
2,5-4EO-PPV(10%)
g ꢀ! M ꢀ! decomp:
235
g ꢀ! M ꢀ! decomp:
6
215
g ꢀ! Sm ꢀ! decomp:
17
215
g ꢀ! Sm ꢀ! decomp:
13
200
g ꢀ! Sm ꢀ! decomp:
31
200
g ꢀ! Sm ꢀ! decomp:
39
200
g ꢀ! Sm ꢀ! decomp:
g; glassy, M; mesophase, Sm; smectic phase, decomp.; thermal decomposition.

432=[1474]
T. Mihara et al.
FIGURE 3 UV-vis spectra of 2,5-4EO-PPV: solid line; neat cast film, broken line;
annealed film.
micro-Brownian motion of the polymer backbone. However, in our case,
glass transition temperatures would be determined by the cooperative
phenomenon composed of the motion of the side chain and the micro-
Brownian motion of the polymer backbone. The motion of the side chain
would be restricted by the formation of the complex of lithium ion and oxy-
gen atom in the EO chain. Glass transition temperatures would increase
with adding LiClO4 because the complex would act as a crosslinking point.
Increase in glass transition temperatures was observed for the mixtures of
8EO-PPV and LiClO4, however the mixtures of 3EO-PPV or 4EO-PPV and
LiClO4 did not show glass transition temperatures. It would not be so easy
to form the complex of lithium salt and oxygen atom in the EO chain for
3EO-PPV and 4EO-PPV, because they had the shorter length of the EO
chain. At first glance, the motion of the side chain would influence glass
transition temperatures of the PPV derivatives, however we considered
that the effect of the motion of the side chain on glass transition tempera-
tures would be emphasized apparently compared to that of the micro-
Brownian of the polymer backbone, because the addition of LiClO4 mainly
influenced the motion of the side chain.
Mesomorphic phase structures of the mixtures were investigated by the
X-ray measurements. A smectic phase was observed for 2, 5-3EO-PPV and
2, 5-4EO-PPV, respectively. The d-spacing of the mixtures was almost same
as that of each PPV derivative. On the other hand, a typical X-ray pattern
for a smectic phase was not observed for the mixtures of lithium salt and
the PPV derivative (3EO-PPV, 4EO-PPV or 8EO-PPV).

Synthesis and Physical Properties of Poly(Phenylene Vinylene)s 433=[1475]
TABLE 3 p-pꢂ Absorption Maximum and Band Gap of PPV Derivatives
p-pꢂ absorption maximum (kmax)=nm
Band gap=eV
Annealed filmc
Polymers
Solutiona
Filmb
Annealed filmc
Filmb
3EO-PPV
4EO-PPV
482
483
488
487
484
545
524
524
545
522
525
508
514
507
482
2.00
1.96
2.03
2.04
2.03
2.05
2.04
2.10
2.07
2.17
8EO-PPV
2,5-3EO-PPV
2,5-4EO-PPV
c
a chloroform solution, bcast film, measured after annealing.
Figure 3 showed UV spectra for the cast and annealed film of 2, 5-4EO-
PPV. The wavelength of the p-pꢂ absorption peak and the band gap of PPV
derivatives were summarized in Table 3. The values of the band gap were
calculated from the wavelength of the edge of the maximal absorption
peak. In the case of the chloroform solution of the PPV derivatives, the
p-pꢂ absorption peaks were observed near 485 nm, while the p-pꢂ absorp-
tion peaks were shown about 520–545 nm for the cast films of the PPV deri-
vatives. Annealing of the cast film of the PPV derivatives resulted in the
blue shift of the absorption peak. This result indicated that the planarity
of the polymer backbone would decrease by annealing. The value of the
band gap slightly increased with annealing. These results also indicated
that the planarity of the polymer backbone would decrease by annealing.
Figure 4 displayed a fluorescence spectrum of the chloroform solution
of 8EO-PPV. The wavelength of the maximum emission peak for the PPV
FIGURE 4 Fluorescence spectrum of 2,5-4EO-PPV in chloroform solution.

434=[1476]
T. Mihara et al.
TABLE 4 Emission Maxima of PPV Derivatives in Chloroform
Solution
Polymers
Emission maximaa
3EO-PPV
4EO-PPV
544
546
547
545
547
8EO-PPV
2,5-3EO-PPV
2,5-4EO-PPV
a in chloroform solution
derivatives was summarized in Table 4. The maximum emission peak of the
fluorescence spectra was detected at about 545 nm for the chloroform
solution of the PPV derivatives. On the other hand, the fluorescence
spectra were not observed for the cast film of these PPV derivatives.
Quantum yields of the PPV derivatives in chloroform solution were
summarized in Table 5. The quantum yields increased with length of the
TABLE 5 Quantum Yields of PPV Derivatives in Chloroform Solution
Polymers
Quantum yieldsa
Quantum yieldsb
3EO-PPV
4EO-PPV
19
28
45
21
30
17
25
42
19
28
8EO-PPV
2,5-3EO-PPV
2,5-4EO-PPV
aRodamine B, bQuinine sulfate in 0.1 M H2SO4 solution.
TABLE 6 Electrical Conductivity of PPV Derivatives
Electrical conductivity (S=cm)
Polymersa
Neatb
Annealed filmc
3EO-PPV
4EO-PPV
2.0 ꢃ 10ꢀ4
3.2 ꢃ 10ꢀ3
5.0 ꢃ 10ꢀ4
8.8 ꢃ 10ꢀ3
6.0 ꢃ 10ꢀ4
1.6 ꢃ 10 ꢀ4
3.0 ꢃ 10ꢀ3
<10ꢀ7
8EO-PPV
2,5-3EO-PPV
2,5-4EO-PPV
6.2 ꢃ 10ꢀ3
7.0 ꢃ 10 ꢀ5
c
a doped with I2 vapor, bcast film, measured after annealing.

Synthesis and Physical Properties of Poly(Phenylene Vinylene)s 435=[1477]
FIGURE 5 Temperature dependence of ionic conductivity for 8EO-PPV: open
circle; LiClO4=EO unit ¼ 0.04, open square; LiClO4=EO unit ¼ 0.07, open triangle;
LiClO4=EO unit ¼ 0.10.
EO chain. 8EO-PPV showed the largest quantum yield of them. Further-
more the quantum yield of the 2,5-3EO-PPV was larger than that of the
3EO-PPV. The same tendency was observed for the quantum yields of
4EO-PPV and 2,5-4EO-PPV. Therefore the quantum yield was affected by
the number and length of the EO chain introduced into the benzene ring
in the polymer backbone.
FIGURE 6 Temperature dependence of ionic conductivity for 2,5-3EO-PPV: open
circle; LiClO4=EO unit ¼ 0.04, open square; LiClO4=EO unit ¼ 0.07.

436=[1478]
T. Mihara et al.
FIGURE 7 Temperature dependence of ionic conductivity for 2,5-4EO-PPV: open
circle; LiClO4=EO unit ¼ 0.04, open square; LiClO4=EO unit ¼ 0.07, open triangle;
LiClO4=EO unit ¼ 0.10.
Electrical conductivity of the PPV derivatives doped with I2 vapor was
summarized in Table 6. The electrical conductivity of the PPV derivatives
was about 10ꢀ3 - 10ꢀ4 Scmꢀ1. The electrical conductivity of the PPV deri-
vatives slightly decreased with annealing. These results showed that the
annealing resulted in decrease in the planarity of the polymer backbone.
Ionic conductivity of the mixtures of LiClO4 and 3EO-PPV or 4EO-PPV
was very low. The low ionic conductivity would originate from the poor
solubility of LiClO4 in these PPV derivatives. The solubility of LiClO4 in
8EO-PPV was higher than that in 3EO-PPV or 4EO-PPV. The solubility of
LiClO4 was influenced by the length of the EO chain. Thermal dependence
of ionic conductivity for the mixture of 8EO-PPV and LiClO4 was shown in
Figure 5. The ionic conductivity for the mixture with 7% of salt concen-
tration was higher than that with other concentration. (This salt concen-
tration means mol% of LiClO4 versus EO unit in the PPV derivatives.) In
the case of the mixture with 10% of salt concentration, the mobility of ions
would decrease due to the crystallization of the salt and decrease in fluidity
of the mixture.
Figures 6 and 7 showed temperature dependence of the ionic conduc-
tivity for 2,5-3EO-PPV and 2,5-4EO-PPV, respectively. In both cases, large
temperature dependence of the ionic conductivity was observed. The ionic
conductivity of these PPV derivatives increased with temperature. Then
the ionic conductivity of the mixture of PPV derivative and LiClO4
increased with the LiClO4 concentration.

Synthesis and Physical Properties of Poly(Phenylene Vinylene)s 437=[1479]
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