Synthesis and double doping behavior of a poly(p-phenylenevinylene)s bearing conjugated side chains

Article abstract of DOI:10.1002/pola.25919

A poly(p-phenylenevinylene) derivative bearing conjugated side chains (polyCPV) was synthesized by Migita-Kosugi-Stille type coupling polycondensation reaction. This polymer contains phenylenevinylene units in both the main chain and the side chains. UV-vis absorption and fluorescence emission spectroscopies revealed a well-developed π-conjugation of the polyCPV. The absorption band of the polymer was extended to long wavelengths. A fluorescent emission maximum of polyCPV is located at considerably longer wavelengths than that of the conjugated side chain monomer. Electron spin resonance measurements of polyCPV confirmed generation of charge species in both the main chain and the side chains via iodine doping.

Full text of DOI:10.1002/pola.25919

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Synthesis and Double Doping Behavior of a Poly(p-phenylenevinylene)s
Bearing Conjugated Side Chains
Hirotsugu Kawashima, Kohsuke Kawabata, Hiromasa Goto
Graduate School of Pure and Applied Sciences, Institute of Materials Science, University of Tsukuba, Tsukuba,
Ibaraki 305-8573, Japan
Correspondence to: H. Goto (E-mail: gotoh@ims.tsukuba.ac.jp)
Received 22 September 2011; accepted 2 January 2012; published online 31 January 2012
DOI: 10.1002/pola.25919
ABSTRACT: A poly(p-phenylenevinylene) derivative bearing
conjugated side chains (polyCPV) was synthesized by Migita-
Kosugi-Stille type coupling polycondensation reaction. This
polymer contains phenylenevinylene units in both the main
chain and the side chains. UV–vis absorption and fluores-
longer wavelengths than that of the conjugated side chain
monomer. Electron spin resonance measurements of poly
CPV confirmed generation of charge species in both the
C
V
main chain and the side chains via iodine doping.
2012
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1530–1538, 2012
cence emission spectroscopies revealed
a well-developed
p-conjugation of the polyCPV. The absorption band of the
polymer was extended to long wavelengths. A fluorescent
emission maximum of polyCPV is located at considerably
KEYWORDS: atomic force microscopy (AFM); conjugated poly-
mers; ESR/EPR; UV–vis spectroscopy
INTRODUCTION Conjugated polymers have attracted much
attention because of their characteristic optical and electro-
chemical properties.1–6 Many kinds of conjugated polymers
have been synthesized for various applications, such as or-
ganic photovoltaic cells, organic light-emitting diodes, and
field-effect transistors.7–11
accepter doping in both the side chain and the main chain,
and stabilization of the polarons along the main chain may
be expected via corporation of the side chain. Two dimen-
sionally distributed polarons in both side chain direction and
main chain direction may be obtained for the polymers.
Conjugated polymers bearing conjugated side chains have
large p-conjugated system distributed from main chain to
the side chain.16,17 To date, several studies of conjugated
side chain polymers have been reported,16–19 and applica-
tions for organic electronic devices based on conjugated
polymers have been carried out.20,21 These polymers have
advantages for extension of absorption bands to long wave-
lengths, and tunability of band gaps with introduction of
conjugated substituents. Intramolecular electronic communi-
cation between the main chain and the side chain through
conjugation structures of the polymers are possible. On the
other hand, drawbacks such as low solubility, difficulty of
construction of the main-chain/side-chain conjugated archi-
tecture due to rigid bulky side chains still remain. Therefore,
a new synthetic strategy and characterization for main-
chain/side-chain conjugated polymers are further required.22
Photo-induced electron transfer in composite of conducting poly-
mers has been studied for conjugated polymers such as poly
(para-phenylenevinylene) (PPV) and C60, and its derivatives. The
charge transfer process is fast and has good efficiency.12,13 This
system is driven by intermolecular interaction between PPV as
an electron donor and C60 as an electron acceptor.
Introduction of flexible side chains to conjugated polymers
improves solubility of resulting polymers. Furthermore, intro-
duction of liquid crystalline substituent onto rigid conjugated
main chain increases solubility and processability and self-
alignable properties.14,15 However, in this case, charge transfer
between side chain and main chain cannot be expected. On
the other hand, we assumed that introduction of conjugated
side chains to conjugated polymers affords intramolecular
interaction between side chain and main chain. This system
affords light accumulation through energy capturing from the
conjugated side chain. Long conjugated side chains increase
susceptibility of photon energy from outside environment.
In this research, we synthesized a conjugated main-chain/
side-chain polymer which has phenylenevinylene units in
both the main chain and the side chain. Generally, conjugated
polymers show low solubility because of rigid and highly
developed p-conjugation. The PPV backbone is known as
As for main chain–side chain-type conjugated polymers,
polarons as a charge carrier can be generated by electron
Additional Supporting Information may be found in the online version of this article.
C
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SCHEME 1 Synthetic routes to poly(p-phenylenevinylene) bearing conjugated side chains (polyCPV) and CSCM derivative (6).
DMF, N,N-dimethylformamide; NBS, N-bromosuccinimide; BPO, benzoyl peroxide; AIBN, N,N-azobisisobutyronitrile.
RESULTS AND DISCUSSION
comparatively flexible structure among the conjugated poly-
mers.23 We synthesized a PPV having conjugated side chains
Synthesis and Processability
Synthetic routes to poly(p-phenylenevinylene) bearing
to improve solubility, and expect electronic communication
between the main chain and the side chains. Optical proper-
ties and vapor-phase iodine doping of the main-chain/side-
chain-type conjugated polymer were further examined.
conjugated side chains (polyCPV) are shown in Scheme 1.
Williamson etherification with an aid of crown ether as a
phase-transfer catalyst afforded compound 1. Next, the
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FIGURE 1 AFM two-dimensional (a) and three-dimensional (b) images of polyCPV film spin-cast from CHCl3. This is a phase image
acquired in tapping mode.
ꢁ
aldehyde group in compound 1 was reacted with the phos-
phonate ester groups of compound 3, according to Horner-
Wadsworth-Emmons reaction. 1,2-Bistributyltin ethylene (vi-
nylene monomer, VM) was synthesized using azobisisobutyr-
onitrile. Finally, the conjugated side chain monomer (CSCM)
and VM were copolymerized by the Migita-Kosugi-Stille cou-
pling reaction. CSCM derivative (6) was also prepared as a
reference material for ESR measurement. A detailed syn-
thetic procedure is described in the Experimental section,
and proton NMR spectra of these compounds are shown in
Supporting Information Figures S1–S6.
of 30ꢀ300 C. The bulky side chains may depress formation
of liquid crystal.
Optical and Electrochemical Properties
Figure 2 shows UV–vis absorption and fluorescence spectra
of polyCPV. Absorption maxima of polyCPV and CSCM are at
339 nm (Table 1). PolyCPV also shows an absorption
shoulder at 448 nm. This indicates that the absorption maxi-
mum at 339 nm is due to p–p* transition of p-distyrylben-
zene moiety in the CSCM unit, and the shoulder at 448 nm
of polyCPV is due to p–p* transition of the main chain.
Although absorption maxima of polyCPV and CSCM are
located at the same wavelength, polyCPV shows an emission
maximum at longer wavelengths than that of CSCM. There-
fore, polyCPV displays the emission from the conjugated
main chain rather than from the conjugated side chain.
These results indicate that polyCPV harvests photon energy
from the conjugated side chains and emits fluorescence from
the conjugated main chain. That is, energy conduction from
the conjugated side chain to the main chain can be occurred
Integrals of the proton NMR spectrum of polyCPV show
good agreement with theoretical values (Supporting Informa-
tion Fig. S6). This result indicates that the polycondensation
reaction afforded the desired polymer. PolyCPV is red, while
CSCM is yellow (Supporting Information Fig. S7). Gel perme-
ation chromatography (GPC) measurements indicated the
number average molecular weight (Mn) of 8600, the weight
average molecular weight (Mw) of 19,700, and the polydis-
persity (Mw/Mn) of 2.29.
Generally, conjugated polymers having conjugated side
chains show low solubility as compared to polymers with
alkyl side chains because of their bulky structure.24,25
PolyCPV, however, dissolves in chloroform, tetrahydrofuran
(THF), and toluene probably due to a flexibility of conjugated
structure of phenylenevinylene. Furthermore, chirality of
alkyl groups in the side chains can provide a further good
film-forming property.26
Atomic force microscopy (AFM) observation for polyCPV film
reveals surface of the film showing pebbles like structure, as
shown in Figure 1. Differential scanning calorimeter meas-
urements were examined for polyCPV (Supporting Informa-
tion Fig. S8). No phase transition was observed in the range
FIGURE 2 UV–vis absorption (solid) and fluorescence emission
(dashed) spectra of PolyCPV (gray) and CSCM (black).
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TABLE 1 Maximum Absorption, Emissiona, and Absolute
TABLE 2 Electrochemical Onset Potentials, Optical Absorption
Onset Wavelengths, and Electronic Energy Levels of PolyCPV
and CSCM
Quantum Yields of PolyCPV and CSCM
b
c
kmax (nm)
Emmax (nm)
Ufe
Ufi
Eox/onset
EHOMO
konset
Eogpt
ELUMO
PolyCPV
CSCM
339/448 (sh)
339
537
0.23
0.11
0.10
0.02
(V)
(eV)
(nm)
(eV)
(eV)
434, 458
PolyCPV
CSCM
0.52
0.47
ꢀ5.27
ꢀ5.22
521
443
2.38
2.80
ꢀ2.89
ꢀ2.42
aExcitation wavelength is 360 nm.
b
Ufe ¼external quantum efficiency.
c
Ufi ¼ internal quantum efficiency.
Electron Spin Resonance Measurements
in polyCPV. Excitation spectrum of polyCPV illustrated a sim-
ilar shape with the absorption spectrum of polyCPV (Sup-
porting Information Fig. S9). Absolute fluorescent quantum
yields of CSCM and polyCPV solution in chloroform were
estimated (Table 1). The results showed improvement of the
internal and external quantum efficiencies due to so-called
polymer effect. Visual images of fluorescence emissions of
the polyCPV and CSCM derivative (Compound 6) are shown
in Figure 3 (Supporting Information Fig. S10).
Next, we discuss generation of charge species of polyCPV in
both main chain and the side chains. In situ doping property
of polyCPV was examined by electron spin resonance (ESR)
spectroscopy. Conjugated polymers before doping are insula-
tors because p-electrons of the polymers have almost no
mobility along the backbone. In this condition, no charge car-
riers, such as holes and excess electrons, exist in the polymer.
A doping process allows a generation of charge carriers for a
p-conjugated system of the conjugated polymers. This doping
process produces a pair of a free radical and a positive charge
along the polymer chain, and this pair behaves as a charge
carrier (Supporting Information Fig. S10). This pair is referred
to as polarons for conducting polymers. The ESR spectroscopy
can detect free radicals of the polarons and allows us to dis-
cuss the charged states of conjugated polymers.30
Cyclic voltammetry measurements for monomer CSCM and
PolyCPV (cast film on Pt) were carried out in acetonitrile so-
lution containing 0.1 M tetrabutylammonium perchlorate at
a scan rate of 100 mV/s. An oxidation peak of polyCPV with
an onset of Eox/onset ¼ 0.52 V (vs. Fc/Fcþ) was observed.
The HOMO level (EHOMO) of polyCPV was estimated to be
ꢀ5.27 eV. The lowest unoccupied molecular orbital (LUMO)
is polyCPV is estimated to be ꢀ2.89 eV, calculated from the
highest occupied molecular orbital (HOMO) energy level and
optical bandgap Eg (¼ 2.38 eV). Electrochemical onset poten-
tials, optical absorption onset wavelengths, and electronic
energy levels of CSCM and polyCPV are summarized in Table
2. These values are well matched with the previously
reported results of alkoxyl-substituted poly(p-phenyleneviny-
lene) derivatives.27–29
Figure 4(aꢀd) shows ESR spectra for polyCPV with in situ
vapor-phase doping of iodine. Line shape of the ESR signal
changed drastically with time. During the initial stage of dop-
ing, a sharp and almost symmetric signal grew with doping
time [Fig. 4(b)]. This stage is designated to be Phase I in this
study. g-Value of a signal at the initial stage Phase I was
2.0032. This value is somewhat low for a conjugated poly-
mer. During the next stage, determined to as Phase II, the
symmetrical signal shape gradually changed [Fig. 4(c)]. In-
tensity of the upward peak decreased and the peak shifted
to low magnetic fields with the doping time, although the
trough remained in the same position. During the Phase II,
g-value of the doped polyCPV also increased to 2.0043 in 60
min. In the next stage, the peak height increased again after
the doping time of 60 min [Fig. 4(d), Phase III] suggesting
generation of a new signal in the entire ESR signal due to
generation of an another charge carrier. After 300 min of the
iodine doping, the ESR signal appeared to be saturated.
g-Value of the signal was 2.0049 after 300 min of the doping
time. This value matched well the reported values for po-
laron states of normal poly(p-phenylenevinylene) deriva-
tives.31,32 Figure 5 shows g-value, ESR intensity, and peak
width plots versus doping time which describe the distinct
behavior of paramagnetic properties of polyCPV. This is a
unique example of the doping behavior observed in the ESR.
To verify this unique behavior on doping of polyCPV, we con-
ducted ESR measurements for compound 6 as a reference
under the same conditions, as shown in Figure 6. This com-
pound exhibited a sharp signal after vapor-phase doping of io-
dine. Peak position of the ESR signals shows no change during
the iodine doping, and g-value of compound 6 was constant
FIGURE 3 Fluorescent emissions of PolyCPV (cast film on
quartz substrate) (a) and compound 6 (cast film on quartz sub-
strate) (b).
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FIGURE 4 ESR spectra of polyCPV after vapor-phase iodine doping for (a) 0ꢀ300 min, (b) 0ꢀ15 min, (c) 16ꢀ60 min, and (d)
61ꢀ300 min.
(g ¼ 2.0035). This value was close to that of polyCPV at the
Phase I. From these results, two different types of unpaired
electrons can be generated in the entire polymer system of
polyCPV. The signals observed by the ESR measurements in
the Phase I for polyCPV may be explained by generations of
radicals in the conjugated side chains, while the ESR signal in
the heavily doped state may be associated with the charge car-
riers in the main chain of the polyCPV. The conjugated side
chains of polyCPV are initially doped during early stages of the
iodine doping, and then, the main chain doping occurs in a
subsequent stage. This side chain doping and main chain dop-
ing behavior can be referred to as ‘‘double doping process.’’
Overlaps between the two ESR signals produce the apparent
asymmetric shapes of the observed spectra during the transi-
tion between these two phases.
FIGURE 5 g-Value, ESR intensity, and peak width plots of
polyCPV as a function of vapor-phase iodine doping time.
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polyCPV, the main chain is characterized by a long conjuga-
tion length as compared to the conjugated side chain.
Therefore, the main chain may be first doped preferentially
before the doping of the side chain. However, the experi-
mental results of ESR measurements suggested a different
conclusion. Therefore, the entire shape of the individual
polymer chain needs to be considered for explanation of
this result.
Bulky side chains in polyCPV wrap around the main chain
as shown in Figure 7. In this arrangement, iodine could
not easily penetrate space between the side chains. Iodine
is not accessible to the main chains in the early stage of
doping because of a mechanical shielding by the side
chains. On the other hand, the conjugated side chains are
located on outside of the main chain, which can have good
contact with vapor-phase iodine. Consequently, the side
chains are doped first and the main chains are gradually
doped next. The two charge carriers may exist independ-
ently in the side-chain/main-chain-conjugated system.
Therefore, two dimensionally spread polarons in both
main chain and side chains directions can be generated by
the heavy doping.
FIGURE 6 ESR spectra of the CSCM derivative (6) after vapor-
phase iodine doping for 0ꢀ90 min.
Generally, a highly developed p-conjugated polymers dis-
play low ionization potential.33 As a result, long effective
conjugation allows good dopable property. In the case of
FIGURE 7 Double doping model of iodine. (a) Restriction of iodine access to the conjugated main chain of polyCPV due to bulky
side chain pseudolayers during the early doping stage (Phase I). (b) Main chain and side chain polarons generated by double-
doping during the heavy doping stage (Phases II and III).
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EXPERIMENTAL
desired material was purified by recrystallization from n-hex-
ane to afford a white solid (0.751 g, 1.78 mmol, 31% yield).
Materials and Instruments
All reagents were purchased from Kanto, Tokyo Kasei, and
Wako and used as received. H NMR spectra of low molecu-
1H NMR (400 MHz, d from TMS (ppm), CDCl3): d 4.54 (s, 4H,
ACH2Br), 7.66 (s, 2H, 3,6H).
1
lar compounds were taken on ECS 400 spectrometer (JEOL)
with chloroform-d1 at room temperature. A1H NMR spec-
trum of polyCPV was taken by AVANCE-600 NMR spectrome-
Synthesis of 1,4-Dibromo-2,5-bis-(diethylphosphinoylme-
thyl)benzene (3)
1
ꢁ
ter (Bruker) with chloroform-d at 60 C. Chemical shifts are
reported in ppm downfield from tetramethylsilane (TMS),
using the solvent’s residual signal as an internal reference.
Matrix-assisted laser desorption ionization time of flight
(MALDI-TOF) mass spectra were recorded on a TOF/TOF
5800 (AB Sciex). Molecular weights of the polymers were
determined by GPC with 5 lm-MIXED-D column (Polymer
Laboratories), PU-980 HPLC pump (Jasco), and MD-915 mul-
tiwavelength detector (Jasco), with THF used as the solvent,
with the instruments calibrated by polystyrene standard.
UV–vis absorption spectra were recorded on a V-630 UV–vis
optical absorption spectrometer (Jasco). Photoluminescence
spectra were recorded on F-4500 fluorescence spectropho-
tometer (Hitachi). Absolute fluorescent quantum yields of
compounds were measured with FP8500 (Jasco). ESR spec-
tra were taken at room temperature using JES-TE200 ESR
spectrometer (JEOL) during in situ vapor-phase doping pro-
cess with iodine.
A
solution of 1,4-dibromo-2,5-bis-bromomethylbenzene
(0.749 g, 1.78 mmol) and triethyl phosphite (0.61 mL, 3.56
mmol) was refluxed for 12 h at 160 ꢁC, then unreacted
triethyl phosphite was removed by evaporation under
reduced pressure. The desired material was purified by
recrystallization from ethyl acetate to afford a pale yellow
solid (0.854 g, 1.59 mmol, 90% yield).
1H NMR (400 MHz, d from TMS (ppm), CDCl3): d 1.28 (t,
12H, AOCH2CH3, J ¼ 7.1 Hz), 3.33 (d, 4H, Ar-CH2APA, JpAH
¼ 20.6 Hz), 4.07 (sept, 8H, AOACH2ACH3, J ¼ 7.1 Hz), 7.64
(d, 2H, 3,6H, J ¼ 1.8 Hz).
Synthesis of CSCM
Sodium methoxide (0.812 g, 15.0 mmol) was added in a so-
lution of 1,4-dibromo-2,5-bis-(diethylphosphinoylmethyl)ben-
zene (0.796 g, 1.48 mmol) in DMF (5 mL) under N2 atmos-
phere at 0 ꢁC and stirred for 30 min. After the color of the
mixture changed from red to green, 4-(3,7-dimethyloctylox-
y)benzaldehyde (0.790 g, 3.01 mmol) was added dropwise
to the mixture and stirred for 2 h at rt. The reaction was
monitored by TLC. Then, the mixture was washed with
water, extracted by dichloromethane, and dried over MgSO4.
After filtration, the solvent was removed in vacuo, and the
crude product was purified by column chromatography
(silica gel, chloroform). The compound was dried in vacuo to
afford a yellow solid (0.778 g, 1.03 mmol, 70% yield).
Synthesis
Synthesis of 4-(3,7-Dimethyloctyloxy)benzaldehyde (1)
A solution of 4-hydroxybenzaldehyde (0.704 g, 5.76 mmol),
18-crown-6-ether (0.099 g, 0.38 mmol), potassium carbonate
(0.797 g, 5.77 mmol), N,N-dimethylformamide (DMF) (3 mL)
was stirred. Then, 1-chloro-3,7-dimethyloctane (1.15 g, 6.49
mmol) was added to the reaction mixture and refluxed for
16 h at 120 ꢁC. The reaction was monitored by thin layer
chromatography (TLC). The mixture was dissolved in
dichloromethane, washed with water thoroughly, extracted
by dichloromethane, and dried over MgSO4. After filtration,
the solvent was removed in vacuo and the crude material
was purified by column chromatography (silica gel, ethyl ac-
etate). The product was dried in vacuo and isolated as a col-
orless liquid (1.20 g, 4.57 mmol, 79% yield).
1H NMR (400 MHz, d from TMS (ppm), CDCl3): d 0.88 (d,
12H, ACH(CH3)2, J ¼ 6.6 Hz), 0.95 (d, 6H, ACH(CH3)ACH2A,
J ¼ 6.4 Hz), 1.13–1.88 (m, 20H, OACH2ACH2ACH(CH3)
A(CH2)3ACH(CH3)2), 4.02 (t, 4H, AOACH2AC9H19, J ¼ 6.8
Hz), 6.90 (d, 4H, 3,5H (side chain benzene) J ¼ 8.7 Hz), 6.99
(d, 2H, Ar-CH¼¼CHAAr-OA, J ¼ 16.0 Hz), 7.21 (d, 2H, Ar-
CH¼¼CHAAr-OA, J ¼ 16.0 Hz), 7.47 (d, 4H, 2,6H (side chain
benzene), J ¼ 8.7 Hz), 7.83 (s, 2H, 3,6H).
1H NMR (400 MHz, d from TMS (ppm), CDCl3): d 0.87 (d,
6H, ACH(CH3)2, J ¼ 6.6 Hz), 0.95 (d, 3H, ACH(CH3)-CH2A, J
¼ 6.4 Hz), 1.18 (m, 6H, ACH(CH3)A(CH2)3A), 1.53 (m, 1H,
ACH(CH3)A), 1.65 (m, 2H, OACH2ACH2A), 1.84 (m, 1H,
ACH(CH3)2), 4.07 (t, 2H, AOACH2A, J ¼ 6.8 Hz), 6.99 (d,
2H, 3,5H, J ¼ 8.7 Hz), 7.82 (d, 2H, 2,6H, J ¼ 8.7 Hz), 9.87 (s,
1H, ACHO).
13C NMR (100 MHz, d from TMS (ppm), CDCl3): d 19.7, 22.6,
24.6, 28.0, 29.8, 36.2, 37.3, 39.2, 66.4, 114.8, 123.4, 128.2,
129.1, 129.2, 129.9, 131.6, 137.2, 159.4.MALDI-TOF MASS:
calcd for C42H56Br2O2, 752.70; found, 752.27.
Synthesis of 1,2-Bis-(tributylstannyl)ethylene (Vinylene
Monomer)
Synthesis of 1,4-Dibromo-2,5-bis-bromomethylbenzene (2)
A solution of 1,4-dibromo-2,5-dimethylbenzene (2.01 g, 7.60
mmol), N-bromosuccinimide (2.70 g, 15.2 mmol), and tetra-
chloromethane (18 mL) was stirred. Then, benzoyl peroxide
(0.017 g, 0.071 mmol) was added, and the reaction mixture
A solution of tributylstannyl acetylene (3.90 g, 11.9 mmol),
tributylstannyl hydride (3.46 g, 11.9 mmol), and azobisisobu-
tylonitrile (0.039 g, 0.24 mmol) was refluxed for 6 h at 100
ꢁC. The reaction was monitored by TLC. Then, the crude
product was washed with water, extracted by dichlorome-
thane, and dried over MgSO4. After filtration, the solvent was
removed in vacuo. Unreacted materials were removed by
evaporation under reduced pressure to obtain pure product.
ꢁ
was refluxed for 24 h at 70 C. The reaction was monitored
by TLC. The crude product was washed with water several
times, extracted by dichloromethane, and dried over MgSO4.
After filtration, the solvent was removed in vacuo, and the
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The product was afforded a colorless liquid (6.58 g, 10.9
mmol, 91.7% yield).
color from red to green, 4-(3,7-dimethyloctyloxy)benzalde-
hyde (0.389 g, 1.48 mmol) was added dropwise to the mix-
ture and stirred for 2 h at rt. The reaction was monitored by
TLC. Then, the mixture was washed with water, extracted by
dichloromethane, and dried over MgSO4. After filtration, the
solvent was removed in vacuo, and the crude product was
purified by column chromatography (silica gel, chloroform).
The compound was dried in vacuo to afford a light yellow
solid (0.355 g, 0.57 mmol, 78% yield).
1H NMR (400 MHz, d from TMS (ppm), CDCl3): d 0.80–096
(m, 30H, Sn-CH2CH2CH2CH3), 1.31 (sext, 12H, Sn-
CH2CH2CH2CH3,
CH2CH2CH2CH3, J ¼ 7.9 Hz), 6.87 (s, 2H, HAC¼¼CAH).
J
¼
7.3 Hz), 1.50 (quint, 12H, Sn-
PolyCPV
A solution of CSCM (0.149 g, 0.198 mmol) and VM (0.124 g,
0.204 mmol) in toluene (3 mL) are stirred for 30 min at 50
ꢁC. Then, tetrakis(triphenylphosphine)palladium (0.009 g,
0.008 mmol) was added to the solution and refluxed for 2
days at 90 ꢁC. After cooling, the mixture was poured into
methanol (50 mL) and washed. The washing procedure was
repeated in three times. The precipitates were isolated by
suction filtration, and dried in vacuo to afford a red solid
(0.071 g, 0.115 mmol, 58% yield).
1H NMR (400 MHz, d from TMS (ppm), CDCl3): d 0.87 (d,
12H, ACH(CH3)2, J ¼ 6.8 Hz), 0.95 (d, 6H, ACH(CH3)ACH2A,
J ¼ 6.8 Hz), 1.15–1.89 (m, 20H, OACH2ACH2ACH(CH3)A
(CH2)3ACH(CH3)2), 2.41 (s, 6H, Ar-CH3), 4.01 (td, 4H,
AOACH2AC9H19, J ¼ 6.8 Hz), 6.88 (d, 4H, 3,5H (side chain ben-
zene) J ¼ 6.9 Hz), 6.92 (d, 2H, Ar-CH¼¼CHAAr-OA, J ¼ 16.0
Hz), 7.15 (d, 2H, Ar-CH¼¼CHAAr-OA, J ¼ 16.0 Hz), 7.39 (s, 2H,
3,6H), 7.44 (d, 4H, 2,6H (side chain benzene), J ¼ 8.7 Hz).
MALDI-TOF MASS: calcd. for C44H62O2, 622.96; found, 622.46.
1H NMR (600 MHz, d from TMS (ppm), CDCl3): d 0.87 (brs,
12H, ACH(CH3)2), 0.95 (m, 6H, ACH(CH3)ACH2A), 1.09–
1.81 (br, m, 20H, OACH2ACH2ACH(CH3)A(CH2)3ACH(CH3)2),
3.97 (brs, 4H, AOACH2AC9H19), 6.00–7.90 (brm, 16H, Ar-
CH¼¼CHAAr (main chain), Ar-CH¼¼CHAAr (side chain), 3,6H
(main chain benzene), 3,5H (side chain benzene), 2,6H (side
chain benzene)).
CONCLUSIONS
We prepared PPV bearing p-conjugated side chains by
Migita-Kosugi-Stille type polycondensation. The polymer
exhibited broad optical absorption bands. The ESR measure-
ments of the polymer during vapor-phase iodine doping
revealed three phases of doping process. Charge carriers
(polarons in the main chain and polarons in the side chains)
are considered to be delocalized over the conjugated side
chains and the main chains. This result implies two dimen-
sionally directed polarons for the p-conjugated polymers.
Synthesis of 1,4-Bis-bromomethyl-2,5-dimethylbenzene (4)
A solution of p-xylene (1.84 g, 17.4 mmol), paraformalde-
hyde (1.02 g), hydrogen bromide (5.1 M of acetic acid solu-
tion, 10 mL, 51.0 mmol), and acetic acid (8 mL) was stirred
for 24 h at 60 ꢁC. The reaction was monitored by TLC. The
solution was neutralized with NaOH aqueous solution and
washed with water several times, extracted by dichlorome-
thane, and dried over MgSO4. Then, the solvent was removed
in vacuo, and the desired material was purified by recrystal-
lization from n-hexane to afford a white solid (0.907 g, 3.11
mmol, 18% yield).
The authors thank Chemical Analysis Division, Research Facil-
ity Center for Science and Technology, University of Tsukuba,
and Glass Work Shop of University of Tsukuba. PL quantum
efficiency measurements were carried out in Jasco (Japan).
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