Synthesis and properties of polyacetylenes having pendant carbazole groups

Article abstract of DOI:10.1021/ma021686d

Five novel carbazole-containing polymers, i.e., poly(3,6-di-tert-butyl-9-prop-2-ynylcarbazole) [poly(t-Bu₂CzPr)], poly(9-but-2-ynylcarbazole) [poly(CzBu)], poly(3,6-di-tert-butyl-9-but-2-ynylcarbazole) [poly(t-Bu₂CzBu)], poly(9-(4-et

Full text of DOI:10.1021/ma021686d

2224
Macromolecules 2003, 36, 2224-2229
Synthesis and Properties of Polyacetylenes Having Pendant Carbazole
Groups
F u m io Sa n d a , Ta k a a k i Ka w a gu ch i, a n d Tosh io Ma su d a *
Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University,
yoto 606-8501, J apan
Nor ih isa Koba ya sh i
Department of Information and Image Sciences, Chiba University, Chiba 263-8522, J apan
Received November 14, 2002; Revised Manuscript Received J anuary 22, 2003
ABSTRACT: Five novel carbazole-containing polymers, i.e., poly(3,6-di-tert-butyl-9-prop-2-ynylcarbazole)
[poly(t-Bu2CzPr)], poly(9-but-2-ynylcarbazole) [poly(CzBu)], poly(3,6-di-tert-butyl-9-but-2-ynylcarbazole)
[poly(t-Bu2CzBu)], poly(9-(4-ethynylphenyl)carbazole) [poly(p-CzPA)], and poly(9-(4-prop-1-ynylphenyl)-
carbazole) [poly(p-CzPPr)] were synthesized by the polymerization of the corresponding carbazole-
containing acetylene monomers using [(norbornadiene)RhCl]2-Et3N, WCl6, MoCl5, TaCl5, and NbCl5 in
conjunction with Sn, Bi, Sb, and Si cocatalysts and W(CO)6-hν/CCl4 catalysts. The UV-vis absorption
band edge wavelengths of poly(t-Bu2CzPr) and poly(p-CzPA) were longer than those of the corresponding
polymers substituted by methyl group at the main chain, poly(t-Bu2CzBu) and poly(p-CzPPr), respectively.
The band edge wavelengths of phenylene-spacer-containing polymers, poly(p-CzPA) and poly(p-CzPPr),
were longer than those of methylene-spacer-containing polymers, poly(t-Bu2CzPr) and poly(t-Bu2CzBu),
respectively. Poly(p-CzPA) obtained by WCl6-n-Bu4Sn-catalyzed polymerization exhibited UV-vis
absorption apparently at a longer wavelength than the MoCl5-n-Bu4Sn-based counterpart did. Poly-
(t-Bu2CzPr) showed photoconductivity. The temperatures for 5% weight loss of the polymers were around
300-350 °C under air.
In tr od u ction
them with an Rh-based catalyst to obtain the corre-
sponding substituted poly(phenylacetylene)s.13 Con-
trolled electrochemical oxidation leads to oxidative
polymerization-cross-linking of the carbazole units
without causing decomposition of the poly(phenylacety-
lene) backbone. The UV-vis spectra of the cross-linked
polymers show two absorption peaks at 350 and 560 nm,
wherein the latter is assignable to cross-linked carbazole
units. The redox potential decreases with increasing the
length of the alkyl chain; i.e., longer alkyl chains tend
to weaken electron-withdrawing effects. Tabata et al.
have reported the synthesis and Rh-catalyzed polym-
erization of several N-alkyl-3-ethynylcarbazole mono-
mers and found that the resulting polymers take a
pseudohexagonal columnar structure in the solid phase.14
Carbazole is a well-known hole-transporting and
electroluminescent unit. Polymers containing carbazole
moieties in the main chain or side chain have attracted
much attention because of their unique properties,
which allow various photonic applications such as
photoconductive, electroluminescent, and photorefrac-
tive materials.1 Recent examples of the polymers con-
taining carbazole moieties in the main chains include
poly(carbazole),2 poly(carbazolylenevinylene),3 and poly-
(carbazolyleneethynylene).4 9-Phenylcarbazoleethynylene-
based dendrimer has been also synthesized.5 On the
other hand, there have been many reports concerning
photoconductive polymers having carbazole moieties in
the side chain such as poly(N-vinylcarbazole) (PVK),
polymethacrylate,6 polymethacrylamide,7 poly(p-phen-
ylenevinylene),8 poly(biphenylenevinylene),9 and poly-
(organophosphazene).10
Polyacetylene derivatives exhibit unique properties
such as semiconductivity, high gas permeability, helix
inversion, and nonlinear optical properties.11 It is
expected that incorporation of carbazole into polyacety-
lene will lead to the development of novel functional
polymers based on synergistic actions of carbazole and
main-chain conjugation. Tang et al. have synthesized
acetylenic monomers containing carbazole chromophores
and polymerized them with WCl6-, WOCl4-, MoCl5-,
MoOCl4-, and NbCl5-Ph4Sn catalysts to obtain the
corresponding polyacetylenes with carbazolyl side groups,
which show photoluminescence and photoconductivity.12
Advincula et al. and we have synthesized carbazole-
substituted phenylacetylene monomers and polymerized
We have previously polymerized N-carbazolylacety-
lene (CzA) with WCl6-based catalysts to obtain the
polymer in good yields.15 The polymers produced with
W catalysts are dark purple solids and mostly soluble
in toluene and chloroform. Poly(CzA) exhibits an ab-
sorption maximum around 550 nm and a band edge
wavelength at 740 nm, showing a large red shift
compared with that of poly(phenylacetylene) [poly(PA)].
Poly(CzA) shows a third-order susceptibility of 18 ×
10-12 esu, which is 2 orders larger than that of poly-
(PA). On the other hand, poly(CzA) obtained by the
polymerization with MoCl5, [(nbd)RhCl]2 (nbd ) nor-
bornadiene), and Fe(acac)3 catalysts is insoluble in any
solvent. We have also polymerized 3-(N-carbazolyl)-1-
propyne with MoCl5- and WCl6-based catalysts to obtain
the polymer in high yields, but the polymer is insoluble
in any solvent.16 We have further polymerized 1-(p-N-
carbazolylphenyl)-2-phenylacetylene with TaCl5-based
catalysts to obtain a yellowish-orange solid polymer,
which is partly soluble in toluene and chloroform. This
* Corresponding
adv.polym.kyoto-u.ac.jp.
author.
E-mail:
masuda@
10.1021/ma021686d CCC: $25.00 © 2003 American Chemical Society
Published on Web 02/27/2003

Macromolecules, Vol. 36, No. 7, 2003
Polyacetylenes 2225
IR (KBr, cm-1): 3049, 2918, 2210 (νCtC), 1597, 1453, 1325,
1325, 1211, 1055, 722. Anal. Calcd for C16H13N: C, 87.64; H,
5.98; N, 6.39. Found: C, 87.85; H, 6.25; N, 6.37.
polymer forms a tough film by solution casting and
shows photoconductivity and redox activity.17
As described above, polyacetylenes with pendant
carbazole are expected to show unique electronic and
photonic functions. However, most of these polymers are
poorly soluble, resulting in difficult elucidation of their
properties. This article deals with the synthesis of novel
soluble carbazole-containing polyacetylenes and their
characterization.
3,6-Di-ter t-bu tyl-9-bu t-2-yn ylcar bazole (t-Bu 2CzBu ). The
title compound was synthesized from 3,6-di-tert-butylcarbazole
and 1-bromo-2-butyne in 40% yield in a manner similar to
t-Bu2CzPr. Mp 170-173 °C. 1H NMR (400 MHz, δ in ppm,
CDCl3): 1.45 (18H, s, -C(CH3)3), 1.73 (3H, s, tC-CH3), 4.93
(2H, s, -CH2-), 7.37-7.54 (4H, m, Ar), 8.09 (2H, s, Ar). 13C
NMR (100 MHz, δ in ppm, CDCl3): 3.50 (tC-CH3), 32.03
(-C(CH3)3), 32.63 (-CH2-N ), 34.66 (-C(CH3)3), 73.60 (tC-
CH3), 79.60 (-CtC-CH3), 108.14, 116.30, 122.97, 123.38,
138.47, 141.98. IR (KBr, cm-1): 3049, 2957, 2226 (νCtC), 1632,
1611, 1478, 1298, 804, 613. Anal. Calcd for C24H29N: C, 86.96;
H, 8.82; N, 4.23. Found: C, 86.71; H, 8.82; N, 4.23.
9-(4-Eth yn ylp h en yl)ca r ba zole (p-CzP A). A solution of
(trimethylsilyl)acetylene (3.14 g, 32 mmol), (Ph3P)2PdCl2 (56
mg, 0.08 mmol), CuI (92 mg, 0.40 mmol), Ph3P (84 mg, 0.32
mmol), and Et3N (40 mL) was stirred at 50 °C for 1 h. A
solution of 9-(4-iodophenyl)carbazole (10 g, 27 mmol) in Et3N
(50 mL) was added, and the resulting solution was stirred at
room temperature overnight. Et3N was removed from the
solution by evaporation to obtain yellow powder. THF (200 mL)
and aqueous 0.5 mol/L NaOH (200 mL) were added to the
residue, and the resulting mixture was stirred at room
temperature overnight. The mixture was concentrated by
rotary evaporation, and ether was added to the residue. The
ether solution was washed subsequently with 5% HCl and
water. The organic layer was dried over anhydrous Na2SO4
and concentrated by rotary evaporation to obtain orange
powder. It was purified by silica gel column chromatography
eluted with n-hexane/ethyl acetate ) 40/1 (volume ratio) and
recrystallization from n-hexane. Yield 5.84 g (81%); mp 102-
103 °C. 1H NMR (400 MHz, δ in ppm, CDCl3): 3.17 (1H, s,
tCH), 7.26-8.19 (12H, Ar). 13C NMR (100 MHz, δ in ppm,
CDCl3): 78.10 (tCH), 82.91 (-CtCH), 109.68, 120.25, 120.36,
121.02, 123.54, 126.07, 126.80, 133.68, 138.10, 140.46. IR (KBr,
cm-1): 3264 (νtC-H), 2100 (νCtC), 1603, 1559, 1451, 1227, 837,
754, 723. Anal. Calcd for C20H13N: C, 89.86; H, 4.90; N, 5.24.
Found: C, 89.77; H, 5.06; N, 4.94.
Exp er im en ta l Section
Mea su r em en ts. 1H and 13C NMR spectra were recorded
on a J EOL EX-400 spectrometer in chloroform-d (CDCl3) using
tetramethylsilane as an internal standard. IR and UV-vis
spectra were measured on a Shimadzu FTIR-8100 and a
J ASCO UV-2200 spectrophotometer, respectively. Melting
points (mp) were measured by a Yanaco micro melting point
apparatus. Elemental analyses were carried out at the Kyoto
University Elemental Analysis Center. The number-average
molecular weights (Mn) of polymers were determined by gel
permeation chromatography (GPC) on a J ASCO GULLIVER
system (PU-980, CO-965, RI-930, and UV-1570) equipped with
polystyrene gel columns (Shodex columns K804, K805, and
J 806), using tetrahydrofuran (THF) as an eluent at a flow rate
of 1.0 mL/min, calibrated by polystyrene standards at 40 °C.
Thermal gravimetric analysis (TGA) was carried out with a
Perkin-Elmer TGA-7.
Eva lu a tion of P h otocon d u ctivity. A 1% w/v solution of
polymer in CHCl3 was coated on an ITO electrode using a spin-
coater at 100 rpm for a period of 30 s. The thickness of the
film coated was 5-7 µm. Au was sputtered on the coated layer
to prepare a counter electrode for the ITO electrode. The
relationships between current and applied voltage for the ITO/
poly(t-Bu2CzPr)/Au cells (effective electrode area 0.06 cm2,
thickness 6 µm) were measured at room temperature under
reduced pressure of ca. 10-2 Torr in the dark and under
photoirradiation (2.5 mW/m2) with a Xe lamp using a ther-
moabsorption filter.
Ma ter ia ls. Unless otherwise stated, reagents were com-
mercially obtained and used without further purification. 3,6-
Di-tert-butylcarbazole18 and 9-(4-iodophenyl)carbazole17 were
synthesized according to the literature. The solvents for
polymerization were purified before use by the standard
methods.
9-(4-P r op -1-yn ylp h en yl)ca r ba zole (p-CzP P r ). n-BuLi
(1.59 M solution in n-hexane, 7.98 mL, 12.6 mmol) was added
slowly to a solution of p-CzPA (2.80 g, 10.5 mmol) in THF (10
mL) at -78 °C under nitrogen, and the resulting solution was
stirred at the temperature for 1 h. A solution of MeI (0.76 mL,
12.6 mmol) in THF (10 mL) was slowly added to the solution
at -78 °C, and the resulting mixture was stirred at room
temperature overnight. Water was added to the mixture to
quench the reaction, and the mixture was extracted with ether.
The organic layer was washed with water, dried over anhy-
drous Na2SO4, and concentrated by rotary evaporation to
obtain a viscous brown liquid. The liquid was purified by silica
gel column chromatography eluted with n-hexane and recrys-
tallization from n-hexane. Yield 350 mg (12%); mp 107-111
°C. 1H NMR (400 MHz, δ in ppm, CDCl3): 2.10 (3H, s, -CH3),
7.27-8.13 (12H, m, Ar). 13C NMR (100 MHz, δ in ppm,
CDCl3): 4.43 (-CH3), 77.20 (tC-CH3), 86.93 (-CtC-CH3),
109.74, 120.07, 120.25, 120.31, 123.45, 125.98, 126.80, 123.96,
137.10, 140.62. IR (KBr, cm-1): 2250 (νCtC), 1601, 1512, 1451,
1231, 835, 749, 723. Anal. Calcd for C21H15N: C, 89.65; H, 5.37;
N, 4.98. Found: C, 89.85; H, 5.63; N, 4.94.
3,6-Di-ter t-bu tyl-9-p r op -2-yn ylca r ba zole (t-Bu 2CzP r ). A
solution of 3,6-di-tert-butylcarbazole (3.0 g, 11 mmol) in
benzene (100 mL) was added to NaH (60%, 0.56 g, 14 mmol,
washed with benzene three times before use) and then
dimethyl sulfoxide (DMSO) (4 mL) at room temperature. The
reaction mixture was stirred for 1 h, and propargyl bromide
(1.31 g, 11 mmol) was added to the mixture. The resulting
mixture was stirred at 50 °C for 3 h. Ether was then added to
the mixture, and the organic phase was washed with water
and aqueous NaCl and dried over anhydrous Na2SO4. It was
concentrated by rotary evaporation, and the residue was
purified by silica gel column chromatography eluted with
n-hexane/ethyl acetate ) 10/1 (volume ratio). Yield 1.37 g
(39%); mp 163-165 °C. 1H NMR (400 MHz, δ in ppm, CDCl3):
1.45 (18H, s, -CH3), 2.22 (1H, s, tCH), 4.98 (2H, s, -CH2-),
7.36-7.53 (4H, m, Ar), 8.09 (2H, s, Ar). 13C NMR (100 MHz,
δ in ppm, CDCl3): 32.01 (-CH3), 32.34 (-CH2-), 34.68
(-C(CH3)3), 71.97 (tCH), 78.17 (-CtCH), 108.07, 116.43,
123.16, 123.51, 138.38, 142.33. IR (KBr, cm-1): 3279 (νtC-H),
2953, 2122 (νCtC), 1632, 1610, 1478, 1298, 806, 677, 613. Anal.
Calcd for C23H27N: C, 87.02; H, 8.57; N, 4.41. Found: C, 86.73;
H, 8.42; N, 4.39.
P olym er iza tion . All the polymerizations were carried out
in a Schlenk tube equipped with a three-way stopcock under
dry nitrogen. The polymerization mixture was poured into a
large amount of methanol to precipitate a polymer. It was
separated from the supernatant by filtration and dried under
reduced pressure.
Sp ectr oscop ic Da ta of th e P olym er s. Poly(t-Bu2CzPr) 1H
NMR (400 MHz, δ in ppm, CDCl3): 0.99 (18H, broad s, -CH3),
3.16 (2H, broad s, -CH2-), 4.71 (1H, broad s, -CHdC ), 7.02
(2H, broad s, Ar), 7.40 (4H, broad s, Ar). IR (KBr, cm-1): 2959,
1717, 1534. Poly(CzBu) IR (KBr, cm-1): 3050, 1485, 1325,
1211, 1154, 1121, 747, 722. Poly(t-Bu2CzBu) 1H NMR (400
MHz, δ in ppm, CDCl3): 1.43 (9H, broad s, -C(CH3)3), 2.29
(3H, broad s, CH3), 5.52 (2H, broad s, -CH2-), 6.87-7.41 (4H,
9-Bu t-2-yn ylca r ba zole (CzBu ). The title compound was
synthesized from carbazole and 1-bromo-2-butyne in 31% yield
in a manner similar to t-Bu2CzPr. Mp 84-87 °C. 1H NMR (400
MHz, δ in ppm, CDCl3): 1.74 (3H, s, -CH3), 4.99 (2H, s,
-CH2-), 7.20-8.15 (8H, m, Ar). 13C NMR (100 MHz, δ in ppm,
CDCl3): 3.48 (-CH3), 32.62 (-CH2-), 73.25 (tC-CH3), 79.91
(-CtC-CH3), 108.80, 119.26, 120.34, 123.10, 125.74, 139. 93.

2226 Sanda et al.
Macromolecules, Vol. 36, No. 7, 2003
Sch em e 1
Sch em e 2
and W catalysts (runs 1-3). The addition of cocatalysts,
Ph3SiH, n-Bu4Sn, Ph4Sn, Ph3Bi, and Ph3Sb, was also
effective to increase the yield and Mn, when toluene and
PhCl were used as the solvents (runs 5-10). Combina-
tion of MoCl5 with Ph4Sn and Ph3Bi was the most
satisfactory to form high-molecular-weight polymers
(runs 7 and 8), but it exhibited multimodal GPC. This
may be due to incomplete solubility of the cocatalysts
in toluene, which may cause formation of plural active
species. Use of 1,4-dioxane as solvent resulted in the
decrease of polymer yield (run 11), presumably because
the monomer was partly insoluble in the solvent under
the condition and/or because the catalyst was deacti-
vated by donor effect of the oxygen of 1,4-dioxane. No
polymer was obtained when cyclohexane was used as
solvent (run 12).
m, Ar), 8.07-8.11 (2H, m, Ar). IR (KBr, cm-1): 2963, 2867,
1
1492, 1296, 880, 803, 612. Poly(p-CzPA) H NMR (400 MHz,
δ in ppm, CDCl3): 6.0-8.2 (broad m). IR (KBr, cm-1): 1509,
1
1451, 747, 722. Poly(p-CzPPr) H NMR (400 MHz, δ in ppm,
CDCl3): 1.4-2.4 (3H, broad m, CH3), 6.4-8.2 (broad m, 12H,
Ar). IR (KBr, cm-1): 1509, 1453, 1316, 747, 723.
Resu lts a n d Discu ssion
Mon om er Syn th esis. Scheme 1 illustrates the syn-
thetic routes for the substituted carbazole-containing
acetylene monomers. t-Bu2CzPr, CzBu, and t-Bu2CzBu
were prepared by alkylation of 3,6-di-tert-butylcarbazole
or carbazole with propargyl bromide or 1-bromo-2-
butyne in 31-40% yields. p-CzPA was synthesized by
Pd-Cu-catalyzed coupling of 9-(4-iodophenyl)carbazole
with (trimethylsilyl)acetylene, followed by desilylation
using aqueous NaOH in 81% yield. p-CzPPr was syn-
thesized by methylation of p-CzPA in 12% yield. All the
monomers were obtained as yellowish-orange powder
after purification by silica gel column chromatography
and successive recrystallization. The structures were
confirmed by 1H and 13C NMR and IR besides elemental
analysis.
P olym er iza tion . Scheme 2 and Table 1 summarize
the conditions and results of the polymerization of the
carbazole-containing novel acetylene monomers, cata-
lyzed by [(nbd)RhCl]2, WCl6, MoCl5, TaCl5, NbCl5, and
W(CO)6-hν in toluene, chlorobenzene (PhCl), 1,4-di-
oxane, cyclohexane, and CCl4 at 30-80 °C for 24 h. The
polymerization of t-Bu2CzPr proceeded homogeneously
to afford the corresponding polymer with Mn ranging
from 1600 to 163 000, except in the case when CCl4 was
used as the solvent (runs 1-12). When [(nbd)RhCl]2-
Et3N was used as the catalyst (run 1), the Mw/Mn ratio
was larger than the values with WCl6 and MoCl5 (runs
2-11). The yield and Mn of the polymer obtained by
WCl6-catalyzed polymerization were very low (run 2).
The addition of n-Bu4Sn was effective to increase the
yield and Mn of the polymer formed (run 3) in a fashion
similar to monosubstituted acetylene polymerization.16,19
The yield and Mn of the polymer obtained by MoCl5-
catalyzed polymerization tended to be high (runs 4-11)
compared with those of the polymer obtained with Rh
The polymerization of CzBu and t-Bu2CzBu was
carried out with TaCl5 and NbCl5 using n-Bu4Sn as
cocatalyst (runs 13-15), because it has been reported
that these metal halides effectively catalyze the polym-
erization of disubstituted acetylenes such as internal
octynes, 1-phenyl-1-propyne, and 1,2-diphenylacetylene
derivatives to give the corresponding polymers with Mn
of ca. 1 000 000.20 The polymer of CzBu was insoluble
in common organic solvents such as MeOH, n-hexane,
toluene, benzene, acetone, ether, THF, CHCl3, DMSO,
and DMF (run 13). On the other hand, the polymer of
t-Bu2CzBu obtained by the polymerization with TaCl5-
n-Bu4Sn was soluble in toluene, benzene, THF, and
CHCl3 (run 14). Incorporation of tert-butyl groups onto
the carbazole ring effectively increased the polymer
solubility as expected. However, no MeOH-insoluble
polymer could be obtained when NbCl5-n-Bu4Sn (run
15) and WCl6-n-Bu4Sn were used as catalyst (run 16).
The polymerization of p-CzPA was carried out with
[(nbd)RhCl]2-Et3N, MoCl5, and WCl6 in conjunction
21
with Sn cocatalysts and W(CO)6-hν/CCl4 (runs 17-
22). It is quite interesting that the polymer obtained
with [(nbd)RhCl]2-Et3N catalyst was insoluble in tolu-
ene, benzene, THF, and CHCl3 (run 17), while the
polymers formed with Mo and W catalysts were soluble
in these solvents (runs 18-22). This is probably due to
the difference of the cis-trans configuration of the
polyacetylene main chains based on the catalysts used.

Macromolecules, Vol. 36, No. 7, 2003
Ta ble 1. P olym er iza tion of Ca r ba zole-Con ta in in g Acetylen e Mon om er sa
Polyacetylenes 2227
c
c
run
monomer
cat.
cocat.
Et3Nd
solvent
toluene
temp (°C)
yieldb (%)
Mn
Mw/Mn
d
1
2
3
4
5
6
7
8
t-Bu2CzPr
t-Bu2CzPr
t-Bu2CzPr
t-Bu2CzPr
t-Bu2CzPr
t-Bu2CzPr
t-Bu2CzPr
t-Bu2CzPr
t-Bu2CzPr
t-Bu2CzPr
t-Bu2CzPr
t-Bu2CzPr
CzBu
t-Bu2CzBu
t-Bu2CzBu
t-Bu2CzBu
p-CzPA
p-CzPA
p-CzPA
[(nbd)RhCl]2
WCl6
WCl6
30
30
30
30
30
30
30
30
30
30
30
30
80
80
80
60
30
30
30
30
30
30
30
30
60
47
13
66
46
68
68
68
63
71
70
24
0
9 100
1 600
8 400
3.20
1.93
1.72
1.76
1.69
1.81
1.46
1.37
1.99
1.77
2.04
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
PhCl
1,4-dioxane
cyclohexane
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
1,4-dioxane
CCl4
n-Bu4Sn
MoCl5
MoCl5
MoCl5
MoCl5
MoCl5
MoCl5
MoCl5
MoCl5
MoCl5
TaCl5
TaCl5
NbCl5
WCl6
[(nbd)RhCl]2
MoCl5
WCl6
51 200
92 800
69 400
148 000e
163 000e
95 200
67 800
33 600
Ph3SiH
n-Bu4Sn
Ph4Sn
Ph3Bi
Ph3Sb
Ph3Sb
Ph3Sb
Ph3Sb
n-Bu4Sn
n-Bu4Sn
n-Bu4Sn
n-Bu4Sn
Et3Nd
n-Bu4Sn
n-Bu4Sn
n-Bu4Sn
Ph4Sn
9
10
11
12
13
14
15
16
17
18
19
20g
21h
22i
23
24
25
60
54
0
f
f
30 000
1.78
0
d
92
27
46
23
86
10
78
39
0
f
10 600
67 600
104 000
62 300
10 000
123 000
101 000
f
1.78
2.17
2.13
4.21
2.11
2.48
1.48
p-CzPA
p-CzPA
p-CzPA
p-CzPPr
p-CzPPr
p-CzPPr
WCl6
WCl6
W(CO)6-hν
TaCl5
NbCl5
WCl6
n-Bu4Sn
n-Bu4Sn
n-Bu4Sn
toluene
toluene
toluene
a
b
[M]0 ) 0.2 M, [cat.] ) [cocat.] ) 10 mM, time 24 h. MeOH-insoluble part. c Determined by GPC eluted with THF, polystyrene
calibration. [Cat.] ) 2 mM, [Et3N] ) 20 mM. e Main peak (area ratio 70%) of multimodal GPC traces. The others were low-molecular-
d
weight oligomer peaks [Mn 4000-5000 (25%) and Mn 900 (5%)]. f Insoluble in THF. [M]0 ) 0.5 M, time 6 h. [M]0 ) 0.5 M, [cat.] )
g
h
i
[cocat.] ) 20 mM. [M]0 ) 0.5 M, [cat.] ) 20 mM, catalytic solution was irradiated by a UV lamp for 1 h before polymerization.
In fact, it has been reported that [(nbd)RhCl]2-Et3N
catalysts afford substituted polyacetylenes with cis-Cd
C backbone, while Mo and W catalysts yield trans Cd
C-rich polyacetylenes.20 The polymerization of p-CzPPr
provided the polymer with Mn over 100 000 in the
presence of mixtures of TaCl5 and NbCl5 with n-Bu4Sn
(runs 23 and 24) but gave no polymer with WCl6 (run
25).
P olym er Str u ctu r e. The polymer structures were
1
examined by H NMR and IR spectroscopies. The 1H
NMR spectrum of [RhCl(nbd)]2-Et3N-based poly(t-Bu2-
CzPr) (run 1 in Table 1) clearly exhibited a signal
assignable to the main-chain cis olefinic proton at 4.71
ppm, indicating cis-transoidal structure.22 The cis
content of the polymer was determined to be quantita-
tive from the integrated peak ratio between the cis vinyl
proton and the methylene protons adjacent to the
nitrogen atom. When W and Mo catalysts were used,
1
the H NMR signals of the formed polymers were very
broad, and no signal assignable to the cis olefinic proton
was observed at 4-6 ppm. It is assumed that the W-
and Mo-based polymers take the trans structure, and
the trans olefinic proton signal overlaps the aromatic
proton signals around 7 ppm. The IR spectra of the
polymers exhibited no absorption due to νCtC at 2100-
2250 cm-1, which were observed in the monomers. In a
similar fashion, poly(t-Bu2CzPr) and poly(p-CzPA) ex-
hibited no IR absorption due to νtC-H at 3279 cm-1
F igu r e 1. UV-vis spectra of poly(t-Bu2CzPr), poly(t-Bu2-
CzBu), poly(p-CzPA), and poly(p-CzPPr) measured in THF.
[poly(t-Bu2CzPr)] and 3264 cm-1 [poly(p-CzPA)]. Oth-
erwise, the spectroscopic patterns of the polymers were
similar to those of the corresponding monomers.
that the methyl group substituted on the main chain
decreases the conjugation. Poly(p-CzPA) and poly(p-
CzPPr) exhibited absorption at longer wavelengths than
poly(t-Bu2CzPr) and poly(t-Bu2CzBu) did, because the
phenylene spacer participates in the main-chain con-
jugation. Interestingly, poly(p-CzPA) obtained by WCl6-
n-Bu4Sn-catalyzed polymerization exhibited UV-vis
absorption band edge apparently at a longer wavelength
than the one obtained by MoCl5-n-Bu4Sn-catalyzed
P olym er P r op er ties. Figure 1 depicts the UV-vis
spectra of poly(t-Bu2CzPr), poly(t-Bu2CzBu), poly(p-
CzPA), and poly(p-CzPPr). All the polymers exhibited
absorption peaks at 300 and 350 nm, which are assign-
able to the carbazole moiety. The absorption bands of
poly(t-Bu2CzPr) and poly(p-CzPA) extend toward longer
wavelength region as compared to those of poly(t-Bu2-
CzBu) and poly(p-CzPPr), respectively. This indicates

2228 Sanda et al.
Macromolecules, Vol. 36, No. 7, 2003
F igu r e 3. Relationships between current and applied voltage
for ITO/poly(t-Bu2CzPr)/Au cells (effective electrode area 0.06
cm2, thickness 6 µm) measured at room temperature under
reduced pressure of ca. 10-2 Torr: (A) without photoirradia-
tion; (B) under photoirradiation (2.5 mW/m2) with a Xe lamp
using a thermoabsorption filter.
F igu r e 2. Appearance of the polymer samples.
polymerization, which may indicate the former polymer
has a main-chain conjugation longer than that of the
latter. The UV-vis spectrum of poly(CzBu) could not
be measured because of the insolubility of the polymer.
Figure 2 summarizes the appearance of the polymer
samples. Clearly the polymer color becomes darker as
the UV-vis absorption expands toward longer wave-
lengths as shown in Figure 1, including the difference
between the two poly(p-CzPA) samples obtained by W-
and Mo-catalyzed polymerizations. It seems that the
extent of main-chain conjugation of poly(CzBu) is nearly
the same as that of poly(t-Bu2CzBu) judging from the
color of the polymer samples. Although introduction of
tert-butyl groups onto the carbazole ring is effective in
increasing the polymer solubility, it is likely that the
tert-butyl groups hardly affect the main-chain conjuga-
tion, because the tert-butyl groups are located at the 3-
and 6-positions of the carbazoyl group, which are distant
from the main chain.
Figure 3 depicts the conductivity of ITO/poly(t-Bu2-
CzPr)/Au. The current was 1 order higher under pho-
toirradiation than that without. This proves that poly-
(t-Bu2CzPr) exhibits photoconductivity. The dark
conductivity of poly(t-Bu2CzPr) was calculated to be ca.
5 × 10-15 S/cm under the electric field of 103-104 V/cm.
This value is 2 orders higher than that of PVK,23
presumably due to π-conjugation of the poly(t-Bu2CzPr)
main chain. It has been reported that the photocurrent/
dark current ratio of PVK is less than 100.24 This value
depends on several factors including light intensity,
illumination wavelength, and electric field. It is impos-
sible to directly compare the photoconductivity of poly-
(t-Bu2CzPr) with that of PVK. However, the results in
Figure 3 clearly indicate that the designed polymer
works as an optoelectronic functional polymer. We
hoped that poly(p-CzPA) showed superior electrical
F igu r e 4. TGA curves of poly(t-Bu2CzPr), poly(CzBu), poly-
(t-Bu2CzBu), poly(p-CzPA), and poly(p-CzPPr) measured in air
with a heating rate of 10 °C/min.
properties than that of poly(t-Bu2CzPr), because the
former polymer exhibits absorption band edge at a
longer wavelength than the latter dose. This is spectral
sensitization due to the effect of the phenylene spacer.
Poly(p-CzPA) may also exhibit higher photoconductivity
than that of poly(t-Bu2CzPr). Unfortunately, however,
the photoconductivity of poly(p-CzPA) could not be
measured because the film prepared by solution casting
was too brittle.
Figure 4 depicts the TGA traces of the polymers. The
temperatures for 5% weight loss of the polymers were
around 300-350 °C under air, which are somewhat
higher than that of poly(PA).25 The weight loss of the
present polymers proceeded more slowly than that of
poly(PA), which may be attributable to the bulky
carbazolyl side chains. The polymers completely lost
their weights around 700 °C.
Su m m a r y
In this article, we have demonstrated the synthesis
of carbazole-containing novel polyacetylenes. Poly(t-Bu2-
CzPr) and poly(p-CzPA) exhibited band edge wave-
lengths longer than those of the corresponding polymers
substituted with a methyl group on the main chain, i.e.,
poly(t-Bu2CzBu) and poly(p-CzPPr), respectively. Poly-
(p-CzPA) and poly(p-CzPPr) exhibited band edge wave-
lengths longer than those of poly(t-Bu2CzPr) and poly-
(t-Bu2CzBu), presumably because the phenylene spacer
participates in the main-chain conjugation. The UV-
vis spectroscopic pattern of poly(p-CzPA) depended on
the catalysts used; i.e., W-based poly(p-CzPA) exhibited

Macromolecules, Vol. 36, No. 7, 2003
Polyacetylenes 2229
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A: Polym. Chem. 2000, 38, 679. (k) Maertens, C.; Dubois,
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wavelength than the Mo-based counterpart, which
indicates that the former polymer has main-chain
conjugation longer than the latter. This finding may
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Ack n ow led gm en t. We acknowledge the financial
support by a Grant-in-Aid for Scientific Research on
Priority Areas from the J apanese Ministry of Education,
Culture, Sports, Science and Technology and by KA-
WASAKI STEEL 21st Century Foundation for the
present study. F.S. is grateful to Konica Imaging Science
Foundation, Kinki Region Invention Center, The Society
of Synthetic Organic Chemistry, J apan, and Fuji Photo
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