Synthesis of hydroxyphenylglycine-derived novel poly(silylenevinylenephenyleneethynylene)s

Article abstract of DOI:10.1016/j.polymer.2011.06.010

The hydrosilylation polymerization of d-(-)-p-hydroxyphenylglycine-derived diethynyl monomers 1p and 1m with dihydrosilanes Si1 and Si2 was carried out using RhI(PPh₃)₃ as a catalyst to give optically active novel poly(silylenevinylenephenyleneethynylene)s [(E)-poly(1p-Si1), (E)-poly(1p-Si2), (E)-poly(1m-Si1), (E)-poly(1m-Si2), and (Z)-poly(1p-Si1)] with number-average molecular weights ranging from 2800 to 17,000 in 41-92% yields. Polymers having (E)- and (Z)-olefin moieties were obtained, wherein the (E)-/(Z)-ratios depended on the reaction conditions. The UV-vis absorption edge of (E)-poly(1p-Si1) was positioned at a wavelength longer than that of (Z)-poly(1p-Si1), indicating that (E)-vinylene-linkage extends the conjugation more largely than the (Z)-counterpart. This was also confirmed by fluorescence spectroscopy. Alkaline hydrolysis of ester moieties of these polymers gave the corresponding polymers having carboxy groups. The (E)-polymers showed different solubility in hydrophobic solvents before and after hydrolysis, but the non-hydrolyzed and hydrolyzed (Z)-polymers exhibited the same solubility.

Full text of DOI:10.1016/j.polymer.2011.06.010

Polymer 52 (2011) 3570e3579
Contents lists available at ScienceDirect
Polymer
journal homepage: www.elsevier.com/locate/polymer
Synthesis of hydroxyphenylglycine-derived novel
poly(silylenevinylenephenyleneethynylene)s
*
Tokiko Ueda, Masashi Shiotsuki, Fumio Sanda
Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Katsura Campus, Nishikyo-ku, Kyoto 615-8510, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
The hydrosilylation polymerization of
D
-(ꢀ)-p-hydroxyphenylglycine-derived diethynyl monomers 1p
Received 6 April 2011
Received in revised form
31 May 2011
Accepted 6 June 2011
Available online 14 June 2011
and 1m with dihydrosilanes Si1 and Si2 was carried out using RhI(PPh3)3 as a catalyst to give optically
active novel poly(silylenevinylenephenyleneethynylene)s [(E)-poly(1p-Si1), (E)-poly(1p-Si2), (E)-
poly(1m-Si1), (E)-poly(1m-Si2), and (Z)-poly(1p-Si1)] with number-average molecular weights ranging
from 2800 to 17,000 in 41e92% yields. Polymers having (E)- and (Z)-olefin moieties were obtained,
wherein the (E)-/(Z)-ratios depended on the reaction conditions. The UVevis absorption edge of (E)-
poly(1p-Si1) was positioned at a wavelength longer than that of (Z)-poly(1p-Si1), indicating that (E)-
vinylene-linkage extends the conjugation more largely than the (Z)-counterpart. This was also confirmed
by fluorescence spectroscopy. Alkaline hydrolysis of ester moieties of these polymers gave the corre-
sponding polymers having carboxy groups. The (E)-polymers showed different solubility in hydrophobic
solvents before and after hydrolysis, but the non-hydrolyzed and hydrolyzed (Z)-polymers exhibited the
same solubility.
Keywords:
Conjugated polymer
Hydroxyphenylglycine
Poly(silylenevinylenephenyleneethynylene)
Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction
regarding poly(silylenevinylene)s bearing chiral substituents have
been reported as far as we know. We have recently synthesized
Silicon-containing polymers are expected as photoresist,
conductive materials, photo- and electroluminescent materials [1].
Recently, conjugated polymers containing siliconecarbon bonds
gather interest because of their high solubility originating from the
optically active poly(phenyleneethynylene)s by the Sonogashirae
Hagihara coupling polymerization of -hydroxyphenylglycine-
D
derived diyne monomers with diethynylbenzene. The polymers
adopt helical structures with predominantly one-handed screw
sense consisting of hydrophobic exterior and hydrophilic interior in
organic solvents [11]. If we utilize such diyne monomers as
components of poly(silylenevinylene)s, we can obtain novel opti-
cally active silicon-containing polymers that possibly form higher-
order structures. In this article, we report the hydrosilylation
polymerization of diethynyl monomers 1p and 1m synthesized
rotatable sep conjugated bond [2]. Various poly(silylenevinylene)s
are synthesized by the hydrosilylation polymerization of hydro-
silanes with diethynyl compounds catalyzed by platinum [3],
rhodium [4], ruthenium [5], iridium [6], and palladium [7]. Among
them, RhI(PPh3)3-catalyzed hydrosilylation polymerization enables
control over regio- and stereostructures of poly(silylenevinylene)s
according to the reaction conditions [8]. Masuda and coworkers
including us have synthesized a series of poly(silylenevinylene)s
[9], some of which show photoluminescence, electroluminescence,
redox property, and undergo photo-isomerization.
Meanwhile, optically active conjugated polymers are under hot
pursuit due to their potential applications such as circularly
polarized photo- and electroluminescent materials and chiral
recognition (separation, catalysis, sensory functions) [10]. Although
there are a vast amount of examples of such polymers, no report
from
D
-(ꢀ)-p-hydroxyphenylglycine with dihydrosilanes Si1 and
Si2 catalyzed by RhI(PPh3)3 (Schemes 1 and 2), and examination of
the optical and photoluminescent properties of the obtaining
polymers [(E)-poly(1p-Si1), (E)-poly(1p-Si2), (E)-poly(1m-Si1), (E)-
poly(1m-Si2), and (Z)-poly(1p-Si1)].
2. Experimental
2.1. Instruments
Mass spectra were measured on a JEOL JMS-T100CS AccuTOF
mass spectrometer or a JEOL JMS-HX110A mass spectrometer. 1H
(400 MHz) and 13C (100 MHz) NMR spectra were recorded on
* Corresponding author. Tel.: þ81 75 383 2591; fax:þ81 75 383 2592.
E-mail address: sanda@adv.polym.kyoto-u.ac.jp (F. Sanda).
0032-3861/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.polymer.2011.06.010

T. Ueda et al. / Polymer 52 (2011) 3570e3579
3571
t-BuOCOHN
CO2Me
average molecular weights (Mn and Mw) and polydispersity
indices (Mw/Mn) of polymers were determined by gel permeation
chromatography (GPC) on a JASCO GULLIVER system (PU-980, DG-
980-50, CO-965, UV-1570, RI-930), columns KF-805 (Shodex) ꢁ 3,
molecular weight limit up to 4 ꢁ 106, eluent THF, column temper-
ature 40 ꢂC, flow rate 1 mL/min; calibrated with polystyrene
standards. Cyclic voltammograms were measured on an HCH
Instruments ALS600A-n electrochemical analyzer.
Me
n H Si
Me
Si
Me
n
H
+
Me
OMe
Si1
1p, 1m
RhI(PPh3)3
in toluene
2.2. Materials
t-BuOCOHN
CO2Me
Thionyl chloride (Wako),
D-(ꢀ)-p-hydroxyphenylglycine
(Wako), di-tert-butyl dicarbonate [(BOC)2O, Tokuyama], 1-bromo-
4-ethynylbenzene (SigmaeAldrich), PdCl2(PPh3)2 (SigmaeAldrich),
CuI (SigmaeAldrich), PPh3 (Wako), ethynyltrimethylsilane (Shin-
Etsu), 1,4-bis(dimethylsilyl)benzene (Wako), and diphenylsilane
(Wako) were purchased or gifted, and used without purification.
RhI(PPh3)3 was prepared according to the literature [12]. Toluene
used for polymerization was distilled over Na prior to use.
OMe
Me
Si
Me
Me
Si
Me
n
(E)-poly(1p-Si1)
(E)-poly(1m-Si1)
t-BuOCOHN
CO2Me
2.3. Monomer synthesis
H
Si
Novel diyne monomers 1p and 1m were synthesized from
-(ꢀ)-p-hydroxyphenylglycine by the route illustrated in Scheme 3.
n
n
+
D
H
Si2
OMe
2.3.1. 30,50-Diiodo-N-
a
-tert-butoxycarbonyl- -p-hydroxyphenyl-
D
glycine methyl ester (i)
Thionyl chloride (8.0 mL, 110 mmol) was added to a dispersion
1p, 1m
RhI(PPh3)3
in toluene
of
D
-(ꢀ)-p-hydroxyphenylglycine (10.2 g, 61 mmol) in MeOH
(100 mL) dropwise at 0 ꢂC over 30 min. The resulting solution was
stirred at room temperature overnight. After removing the solvent,
the residual mass was washed with Et2O to obtain white solid. A
portion of the solid (13.1 g, 60.3 mmol) and NaHCO3 (10 g,
119 mmol) were dissolved in distilled water (100 mL). After
checking the solution became basic, a solution of (BOC)2O (16.0 g,
73.5 mmol) in 1,4-dioxane (50 mL) was added to the solution at
t-BuOCOHN
CO2Me
OMe
ꢂC. The resulting solution was stirred at room temperature
Si
0
n
overnight. After neutralizing the solution with 2M HCl, the result-
ing solution was extracted with AcOEt. The organic layer was
washed with saturated aqueous NaHCO3, and saturated aqueous
NaCl. It was dried over anhydrous MgSO4 and concentrated on
(E)-poly(1p-Si2)
(E)-poly(1m-Si2)
Scheme 1. Hydrosilylation polymerization of diethynyl monomers 1p and 1m with
dihydrosilanes Si1 and Si2 giving (E)-polymers.
a
rotary evaporator to obtain N-
hydroxyphenylglycine methyl ester as white powder quantitatively.
N- -tert-butoxycarbonyl- -p-hydroxyphenylglycine methyl ester
a-tert-butoxycarbonyl-D-p-
a JEOL EX-400 or a JEOL AL-400 spectrometer. IR spectra were
measured on a JASCO FTIR-4100 spectrophotometer. Melting points
(mp) were measured on a Yanaco micro melting point apparatus.
a
D
(15.2 g, 54.0 mmol), NaCl (12.6 g, 216 mmol), and NaIO4 (11.6 g,
54.0 mmol) were dissolved in AcOH/H2O [9/1 (v/v), 180 mL]. The
mixture was stirred for 15 min. Then, KI (26.9 g, 162 mmol) was
added to the mixture at 0 ꢂC, and the resulting mixture was stirred
at 40 ꢂC for 6 h. After H2O (500 mL) was added, the solution was
extracted with CHCl3. The organic layer was washed first with 1 M
aqueous Na2S2O3 and saturated aqueous NaCl, dried over anhy-
drous MgSO4, and concentrated on a rotary evaporator. The residue
was purified by silica gel column chromatography eluted with
hexane/AcOEt [4/1 (v/v)] to obtain (i) as white powder in 80% yield
Specific rotations ([a]D) were measured on a JASCO DIP-1000 digital
polarimeter. CD, UVevis and fluorescence spectra were measured
using a quartz cell (path length: 1 cm) on JASCO J-820, V-550 and
FP-750 spectrophotometers, respectively. Number- and weight-
(23.0 g, 43.1 mmol) [13]. 1H NMR (400 MHz, CDCl3):
d 1.43 [s, 9H,
e(CH3)3], 3.74 (s, 3H, eCO2CH3), 5.17 (s, 1H, eNHCHe), 5.61 (s, 1H,
eNHCOe), 5.81 (br, 1H, eOH), 7.66 (s, 2H, Ar).
a-tert-butoxycarbonyl-D
2.3.2. 30,50-Diiodo-N- -40-methoxyphenyl-
glycine methyl ester (ii)
Compound (i) (23.0 g, 43.1 mmol) and K2CO3 (8.93 g, 64.7 mmol)
were dissolved in acetone (150 mL). MeI (3.22 mL, 51.7 mmol) was
added to the solution at 0 ꢂC, and the resulting mixture was heated
with refluxing for 3 h. The mixture was poured into iced water, and
the mixture was extracted with CHCl3. The organic layer was
Scheme 2. Hydrosilylation polymerization of diethynyl monomer 1p with dihy-
drosilane Si1 giving a (Z)-polymer.

3572
T. Ueda et al. / Polymer 52 (2011) 3570e3579
Scheme 3. Synthesis of monomers 1p and 1m.
washed with saturated aqueous NaCl, dried over anhydrous MgSO4,
and concentrated on a rotary evaporator to obtain yellow solid in
dried over anhydrous MgSO4 and concentrated on a rotary evapo-
rator to obtain crude 30,50-bis[(4-bromophenyl)ethynyl]-N-
-tert-
butoxycarbonyl-
-40-methoxyphenylglycine methyl ester as brown
a
95% yield (22.5 g, 41.1 mmol) [12]. 1H NMR (400 MHz, CDCl3):
d
1.43
D
[s, 9H, e(CH3)3], 3.75 (s, 3H, eCO2CH3), 3.84 (s, 3H, eOCH3), 5.23 (s,
1H, eNHCHe), 5.77 (s, 1H, eNHCOe), 7.76 (s, 2H, Ar).
solid. It was dissolved in THF/Et3N [5/11 (v/v), 320 mL], and
PdCl2(PPh3)2 (618 mg, 0.88 mmol), CuI (671 mg, 3.5 mmol), PPh3
(692 mg, 2.64 mmol) and ethynyltrimethylsilane (16.0 mL,
113 mmol) were added to the solution. The resulting mixture was
stirred at 50 ꢂC under nitrogen overnight. After the workup process
with a manner similar to that described above, obtained brown
solid was dissolved in THF/MeOH [1/1 (v/v), 220 mL], then K2CO3
(12.2 g, 88.0 mmol) was added to the solution at 0 ꢂC. This solution
was stirred at room temperature for 1 h. After filtration and
concentration on a rotary evaporator, residual mass was dissolved
in CHCl3. The solution was washed with 1.0 M HCl, saturated
aqueous NaHCO3, then saturated aqueous NaCl. It was dried over
anhydrous MgSO4 and concentrated on a rotary evaporator to
2.3.3. Bis[(4-ethynylphenyl)ethynyl]-N-
a-tert-butoxycarbonyl-D-
40-methoxyphenylglycine methyl ester (1p)
A solution of (ii) (24.1 g, 44.0 mmol), 1-bromo-4-ethynyl-
benzene (16.1 g, 89.1 mmol), PdCl2(PPh3)2 (618 mg, 0.88 mmol),
CuI (671 mg, 3.5 mmol) and PPh3 (692 mg, 2.64 mmol) in THF/Et3N
[2/5 (v/v), 350 mL] was stirred at room temperature under nitrogen
overnight. The resulting mixture was filtered, and the filtrate was
concentrated on a rotary evaporator. The residual mass was dis-
solved in CHCl3. The organic layer was washed with 1.0 M HCl,
saturated aqueous NaHCO3, then saturated aqueous NaCl. It was
Table 1
Synthesis of (E)- and (Z)-rich polymers.a
Run
Method
Monomers
Cat (mM)
Temp (ꢂC)
Time (h)
Polymer
Yieldc (%)
Mn
Mw/Mn
E/Ze
[a
]
d
d
f
(ꢂ)
D
1
2
3
4
5
6
7
8
1
1
1
1
1
1
2
2
2
2
2
1p þ Si1
1p þ Si1
1p þ Si2
1p þ Si2
1m þ Si1
1m þ Si2
1p þ Si1
1p þ Si1
1p þ Si1
1p þ Si1
1p þ Si1
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
0.2
0.1
30
60
60
80
60
80
0
30
60
6
0.5
24
15
1
38
24
6
0.5
38
75
80
59
91
91
90
61
41
79
92
65
12,000
14,000
6600
2.8
2.6
2.1
3.5
5.5
3.8
100/0
97/3
ꢀ6.0
ꢀ3.5
e g
100/0
100/0
79/21
100/0
100/0
94/6
100/0
29/71
25/75
11,000
10,000
6300
þ3.5
ꢀ3.7
ꢀ4.8
e g
e
e
g
g
g
6500
1.8
3.4
4.4
2.7
e
9
17,000
12,000
2800
þ2.3
ꢀ9.9
eg
10b
11
25/50
0
25 days
a
[1p or 1m]0 ¼ [Si1 or Si2]0 ¼ 0.1 M in toluene.
[1p]0 ¼ [Si1]0 ¼ 0.2 M in toluene.
MeOH-insoluble part.
b
c
d
e
f
Estimated by GPC, eluent THF, PSt standards.
Determined by 1H NMR.
Measured in THF, c ¼ 0.1 g/dL.
Not determined.
g

T. Ueda et al. / Polymer 52 (2011) 3570e3579
3573
obtain brown solid. The residue was purified by silica gel column
chromatography eluted with hexane/AcOEt [4/1 (v/v)] and recrys-
tallization twice to obtain 1p as slightly yellow powder in 29% yield
161.6, 170.9. HRMS. Calcd for C35H29NO5 (m/z) [M þ NH4]þ
561.2384. Found: 561.2397.
(6.99 g, 12.9 mmol). Mp 126e127 ꢂC [
a]
ꢀ1.2ꢂ (c ¼ 0.100 g/dL in
2.3.4. 30,50-Bis[(3-ethynylphenyl)ethynyl]-N-
-40-methoxyphenylglycine methyl ester (1m)
a-tert-butoxycarbonyl
D
THF at room temperature). 1H NMR (400 MHz, CDCl3):
d
1.44 [s, 9H,
-D
e(CH3)3], 3.20 (s, 2H, eChCH), 3.75 (s, 3H, eCO2CH3), 4.13 (s, 3H,
eOCH3), 5.27 (s,1H, eNHCHe), 5.66 (s,1H, eNHCOe), 7.41e7.49 (m,
The title compound was synthesized in a manner similar to 1p.
Yield 28% (white solid). Mp 136e137 ꢂC [
a]
D þ2.0ꢂ (c ¼ 0.100 g/dL in
10H, Ar). 13C NMR (100 MHz, CDCl3):
d
28.3, 53.0, 56.6, 61.4, 79.1,
THF at room temperature). 1H NMR (400 MHz, CDCl3):
d 1.46 [s, 9H,
80.4, 83.2, 86.7, 93.8, 117.6, 122.2, 123.3, 131.3, 132.0, 132.3, 154.5,
e(CH3)3], 3.14 (s, 2H, eChCH), 3.78 (s, 3H, eCO2CH3), 4.13 (s, 3H,
eOCH3), 5.28 (s, 1H, eNHCHe), 5.68 (s, 1H, eNHCOe), 7.28e7.69
(m, 10H, Ar). 13C NMR (100 MHz, CDCl3):
d 28.3, 53.0, 56.6, 61.4,
78.0, 80.4, 82.6, 85.4, 93.3, 117.6, 122.5, 123.3, 128.5, 131.8, 132.1,
132.4, 135.0, 154.7, 161.7, 171.0. HRMS. Calcd for C35H29NO5 (m/z)
[M þ Na]þ 566.1943. Found: 566.1932.
2.4. Hydrosilylation polymerization
2.4.1. Synthesis of (E)-polymers [(E)-poly(1p-Si1), (E)-poly(1p-Si2),
(E)-poly(1m-Si1), and (E)-poly(1m-Si2)]: typical procedure
All the polymerizations were carried out under nitrogen in
a glass tube equipped with a three-way stopcock. A typical exper-
imental procedure for the polymerization of 1p with 1,4-
bis(dimethylsilyl)benzene (Si1) is given below. A solution of 1p
(163.3 mg, 0.300 mmol), RhI(PPh3)3 (6.10 mg, 6.00
mmol) and 1,4-
bis(dimethylsilyl)benzene (Si1, 66.3 L, 0.300 mmol) in toluene
m
(3 mL) was stirred at 60 ꢂC for 0.5 h. After that, the resulting
mixture was poured into MeOH (250 mL) to precipitate a polymer.
It was separated by filtration using a membrane filter (ADVANTEC
T300A047A) and dried under reduced pressure.
2.4.2. Synthesis of (Z)-poly(1p-Si1): typical procedure
All the polymerizations were carried out under nitrogen. A
solution of RhI(PPh3)3 (1.1 mg, 1.0 mmol) and 1,4-bis(dimethylsilyl)
benzene (Si1, 1.0 mmol) in toluene (1.0 mL) was stirred for 1 h. A
portion of this solution (0.1 mL) was fed into a screw-capped glass
tube, and the solution was further stirred at 0 ꢂC for 1 h. Then 1p
(54.5 mg, 0.1 mmol) and toluene (0.5 mL) were added to the
solution at 0 ꢂC. The resulting mixture was allowed to warm to
room temperature over a period of 2 h, and then stirring was
continued at room temperature for 14 h, at 40 ꢂC for 4 h, and at
50 ꢂC for 20 h. The polymer was isolated in a manner similar to (E)-
polymers.
Fig. 1. UVevis spectra of 1p, 1m, and the polymers measured in THF (c ¼ 6.44e7.59
ꢁ 10ꢀ6 M).
Fig. 2. Photograph of THF solutions of 1p (left), (Z)-poly(1p-Si1) (center) and (E)-
poly(1p-Si1) (right) (c ¼ 1 mg/mL).

3574
T. Ueda et al. / Polymer 52 (2011) 3570e3579
2.5. Alkaline hydrolysis of ester groups of the polymers: typical
procedure
2H, eCH ¼ CHe), 7.04 (d, J ¼ 18.8 Hz, 2H, eCH ¼ CHe), 7.36e7.64
(m, 20H, Ar). IR (cmꢀ1, KBr): 3423, 2977, 1747, 1718, 1591, 1245, 1163,
999, 780, 700.
Aqueous NaOH (1 M, 0.17 mL) was added to a solution of (E)-
(Z)-Poly(1p-Si1) (run 10 in Table 1) 1H NMR (400 MHz, CDCl3):
poly(1p-Si1) (40 mg, 54
m
mol) in THF (1.25 mL) dropwise at 0 ꢂC, and
d 0.30e0.45 [br, 12H, eSi(CH3)2e], 1.44 [s, 9H, e(CH3)3], 3.73 (s, 3H,
then the resulting mixture was stirred at 50 ꢂC for 12 h. The reaction
mixture was poured into 0.5 M aqueous citric acid (100 mL) to
precipitate a polymer. It was separated by filtration using a membrane
filter (ADVANTEC H100A047A) and dried under reduced pressure.
eCO2CH3), 4.12 (s, 3H, eOCH3), 5.25 (s, 1H, eNHCHe), 5.63 (s, 1H,
eNHCOe), 6.05 [d, J ¼ 14.8 Hz, 2H, eCH ¼ CHe, (Z)-vinyl protons],
6.62 [d, J ¼ 19.0 Hz, 2H, eCH ¼ CHe, (E)-vinyl protons], 6.92 [d,
J ¼ 19.0 Hz, 2H, eCH ¼ CHe, (E)-vinyl protons], 7.23e7.59 [m, 16H,
Ar and (Z)-vinyl protons]. IR (cmꢀ1, KBr): 3432, 2957, 1746, 1719,
1602, 1507, 1250, 1162, 1132, 816.
2.6. Spectroscopic data of the polymers
(E)-Poly(1p-Si1)-hydrolyzed 1H NMR (400 MHz, DMSO-d6):
(E)-Poly(1p-Si1) (run 1 in Table 1) 1H NMR (400 MHz, CDCl3):
d
0.22e0.41 [br, 12H, eSi(CH3)2e], 1.37 [s, 9H, e(CH3)3], 4.05 (s, 3H,
eOCH3), 5.14 (s, 1H, eNHCHe), 6.68e6.82 (m, 2H, eCH ¼ CHe),
d
0.30e0.45 [br, 12H, eSi(CH3)2e], 1.44 [s, 9H, e(CH3)3], 3.75 (s, 3H,
6.87e7.09 (m, 2H, eCH ¼ CHe), 7.22e7.55 (m, 14H, Ar). IR (cmꢀ1
,
eCO2CH3), 4.14 (s, 3H, eOCH3), 5.26 (s, 1H, eNHCHe), 5.63 (s, 1H,
eNHCOe), 6.61 [d, J ¼ 18.8 Hz, 2H, eCH ¼ CHe], 6.92 [d, J ¼ 18.8 Hz,
2H, eCH ¼ CHe], 7.45e7.63 (m,14H, Ar). IR (cmꢀ1, KBr): 3423, 2954,
1750, 1718, 1602, 1507, 1250, 1162, 1134, 818.
KBr): 3423, 2955, 1719, 1602, 1507, 1249, 1161, 1133, 817.
(E)-Poly(1p-Si2)-hydrolyzed 1H NMR (400 MHz, DMSO-d6):
d
1.40 [s, 9H, e(CH3)3], 4.10 (s, 3H, eOCH3), 5.16 (s, 1H, eNHCHe),
(E)-Poly(1p-Si2) (run 4 in Table 1) 1H NMR (400 MHz, CDCl3):
1.44 [s, 9H, e(CH3)3], 3.75 (s, 3H, eCO2CH3), 4.15 (s, 3H, eOCH3),
6.94e6.96 (m, 2H, eCH ¼ CHe), 7.09e7.13 (m, 2H, eCH ¼ CHe),
7.42e7.70 (m, 20H, Ar). IR (cmꢀ1, KBr): 3422, 2976, 1718, 1600, 1507,
1243, 1159, 1111, 996, 795, 699.
d
5.26 (s, 1H, eNHCHe), 5.64 (s, 1H, eNHCOe), 6.88 (d, J ¼ 19.0 Hz,
2H, eCH ¼ CHe), 7.01 (d, J ¼ 19.0 Hz, 2H, eCH ¼ CHe), 7.17e7.63
(m, 20H, Ar). IR (cmꢀ1, KBr): 3423, 2975, 1746, 1718, 1599, 1509,
1244, 1161, 1111, 997, 797, 700.
(E)-Poly(1m-Si1)-hydrolyzed 1H NMR (400 MHz, DMSO-d6):
d
1.35 [s, 9H, e(CH3)3], 4.05 (s, 3H, eOCH3), 5.16 (s, 1H, eNHCHe),
6.72e6.82 (m, 2H, eCH ¼ CH-), 6.82e7.08 (m, 2H, eCH ¼ CHe),
7.08e7.87 (m, 20H, Ar). IR (cmꢀ1, KBr): 3423, 2955, 1719,1592, 1475,
1249, 1161, 1133, 987, 845, 780.
(E)-Poly(1m-Si1) (run 5 in Table 1) 1H NMR (400 MHz, CDCl3):
0.29e0.45 [br, 12H, eSi(CH3)2e], 1.43 [s, 9H, e(CH3)3], 3.74 (s, 3H,
d
(E)-Poly(1m-Si2)-hydrolyzed 1H NMR (400 MHz, DMSO-d6):
eCO2CH3), 4.14 (s, 3H, eOCH3), 5.26 (s, 1H, eNHCHe), 5.62 (s, 1H,
eNHCOe), 6.04 [d, J ¼ 14.8 Hz, 2H, eCH ¼ CHe, (Z)-vinyl protons],
6.61 [d, J ¼ 19.2 Hz, 2H, eCH ¼ CH-e (E)-vinyl protons], 6.91 [d,
J ¼ 19.2 Hz, 2H, eCH ¼ CHe, (E)-vinyl protons], 7.19e7.62 (m, 14H,
Ar). IR (cmꢀ1, KBr): 3423, 2953, 1749, 1719, 1591, 1477, 1249, 1161,
1132, 987, 843, 782.
d
1.35 [s, 9H, e(CH3)3], 4.07 (s, 3H, eOCH3), 5.16 (s, 1H, eNHCHe),
6.93e6.99 (m, 2H, eCH ¼ CHe), 7.03e7.15 (m, 2H, eCH ¼ CHe),
7.42e7.82 (m, 20H, Ar). IR (cmꢀ1, KBr): 3422, 2977, 1718, 1591, 1477,
1246, 1161, 998, 778, 700.
(Z)-Poly(1p-Si1)-hydrolyzed 1H NMR (400 MHz, DMSO-d6):
(E)-Poly(1m-Si2) (run 6 in Table 1) 1H NMR (400 MHz, CDCl3):
d
0.23e0.42 [br, 12H, eSi(CH3)2e], 1.38 [s, 9H, e(CH3)3], 4.04 (s, 3H,
eOCH3), 5.28 (s, 1H, eNHCHe), 6.06e6.13 [m, 2H, eCH ¼ CHe, (Z)-
d
1.42 [s, 9H, e(CH3)3], 3.73 (s, 3H, eCO2CH3), 4.13 (s, 3H, eOCH3),
vinyl protons], 6.62e6.86 [m, 2H, eCH ¼ CHe, (E)-vinyl protons],
5.25 (s, 1H, eNHCHe), 5.62 (s, 1H, eNHCOe), 6.93 (d, J ¼ 18.8 Hz,
Fig. 3. UVevis spectra of (E)- and (Z)-model compounds predicted by the DFT (B3LYP/6-31G*) calculation.

T. Ueda et al. / Polymer 52 (2011) 3570e3579
3575
Fig. 5. Photograph of THF solutions (c ¼ 1 mg/mL) of 1p (left), (Z)-poly(1p-Si1)
(center), and (E)-poly(1p-Si1) (right) under irradiation of light (365 nm).
Polymers with Mn’s ranging from 2800 to 17,000 were obtained in
41e92% yields as listed in Table 1. The polymerization was properly
monitored by sampling a small portion of the reaction mixture. The
reaction was continued until a powdery polymer got precipitated
when the sample solution was poured into a large amount of MeOH.
When a diyne, a dihydrosilane, and RhI(PPh3)3 were mixed simul-
taneously (runs 1e6, method 1), diyne 1p gavepolymers with higher
Mn’s in higher yields in shorter reaction times than 1m did. In
a similar fashion, dihydrosilane Si1 was more satisfactory than Si2. It
seems that the higher polymerizabilities of 1p and Si1 than those of
1m and Si2 come from the less steric hindrance around the diyne
and hydrosilane parts, respectively. The polymer yield and Mn
becamehighbyraising temperature. Theregio- andstereostructures
of the polymers were examined by 1H NMR spectroscopy. It was
confirmed that the hydrosilylation took place regioselectively as
illustrated in Scheme 1. No 1H NMR signal assignable to
a-adducts
was observed [14] in the all cases as reported in RhI(PPh3)3-cata-
lyzed hydrosilylation [8d]. Polymers having olefin moieties with (E)-
form were obtained almost exclusively except for run 5.
We tried to obtain polymers with (Z)-form by premixing 1p
with the Rh catalyst (runs 7e11, method 2) according to the
literature [8d]. However, (Z)-polymers did not form but (E)-rich
polymers regardless of the reaction temperature when the catalyst
Table 2
Alkaline hydrolysis of the polymers.a
polymer
yieldb (%)
Mn
Mw/Mn
[a]
D
c
c
d
Fig. 4. Fluorescence spectra of 1p, 1m, and the polymers excited at the lmax wave-
length measured in THF (c ¼ 5.89e7.59 ꢁ 10ꢀ7 M).
(E)-poly(1peSi1)-hydrolyzede
(E)-poly(1peSi2)-hydrolyzedf
(E)-poly(1meSi1)-hydrolyzedg
(E)-poly(1meSi2)-hydrolyzedh
(Z)-poly(1peSi1)-hydrolyzedi
88
91
91
96
74
9100
6600
8500
5300
8300
3.7
3.6
4.0
3.5
2.6
ꢀ13.6
ꢀ1.1
ꢀ0.9
þ4.9
ꢀ6.1
6.86e7.07 [m, 2H, eCH ¼ CHe, (E)-vinyl protons], 7.25e7.52 (m,
14H, Ar). IR (cmꢀ1, KBr): 3423, 2954, 1746, 1719, 1602, 1507, 1249,
1161, 1132, 817.
a
Conditions : in THF, 50 ꢂC, 2e12 h.
b
c
Insoluble part in 0.5 M aqueous citric acid.
Estimated by GPC, eluent THF, PSt standards, where the carboxy groups in the
3. Results and discussion
polymers were transformed into methyl ester groups using TMSCHN2.
d
Measured in THF, c ¼ 0.1 g/dL.
e
Sample: run 2 in Table 1.
3.1. Hydrosilylation polymerization
f
Sample: run 4 in Table 1.
Sample: run 5 in Table 1.
Sample: run 6 in Table 1.
g
h
The hydrosilylationpolymerization of 1p and 1mwith Si1 and Si2
was carried out using RhI(PPh3)3 as a catalyst at 0e80 ꢂC in toluene.
i
Sample: run 10 in Table 1.

3576
T. Ueda et al. / Polymer 52 (2011) 3570e3579
concentration was 2.0 mM (runs 7e9). On the other hand, (Z)-rich
polymers formed when the catalyst concentrations were
decreased to 0.2 and 0.1 mM (runs 10 and 11). The possible reason
for the formation of (Z)-rich polymers is suppression of isomeri-
zation from (Z)-form to (E)-form [15]. Since the Rh complex
catalyzes the olefin isomerization as well as hydrosilylation, it is
considered that decreasing the Rh concentration enabled the
isolation of (Z)-rich polymers. (Z)-Selectivity was somewhat
improved by decreasing the reaction temperature from 25 to 50 to
3.2. Alkaline hydrolysis of the polymers
Poly(phenyleneethynylene)s substituted with polar groups are
amphiphilic. Their backbones are hydrophobic, whereas the polar
side groups control hydrophilic interactions. This amphiphilic
character leads to folding of main chains to adopt helical confor-
mations in polar media. Oligo(m-phenyleneethynylene)s carrying
hydrophilic short ethylene glycol chains fold into helical confor-
mations, which are thermodynamically driven by solvophobic
effects [18]. Amphiphilic poly(m-phenyleneethynylene)s undergo
conformational transition that is consistent with folding of the
main chains into helices [19]. Thus we focused on the methyl ester
part of the present polymers. As mentioned above, it seems that the
polymers do not adopt chiral conformations. By hydrolyzing the
ester moieties into carboxy, it is expected that the polymers
transform into regulated structures based on the increase of
amphiphilicity and possible formation of hydrogen bonding
between the carboxy groups. Table 2 summarizes the results of
hydrolysis of the polymers by NaOH. Polymers bearing carboxy
groups were obtained in 74e96% yields. The molecular weights of
the polymers were measured by transforming the carboxy groups
of the formed polymers into methyl esters again using TMSCHN2,
because the polymers having carboxy groups were not eluted out
from GPC columns presumably due to the high affinity with poly-
styrene gels. The Mn’s of the polymers became 60e85% of those
0
ꢂC. There was no evidence for formation of
cases as well.
Fig. 1 shows the UVevis spectra of the obtained polymers
together with those of diynes 1p and 1m. The max’s of the 1p-based
a-adducts in these
l
(E)-polymers were 12e14 nm red-shifted from that of 1p, indi-
cating the extension of conjugation of the polymers compared to
that of 1p. On the other hand, the lmax’s of the 1m-based polymers
were not red-shifted but rather blue-shifted from that of 1m.
The m-phenylenevinylenesilylene linkage seems to have poor
conjugation.
The lmax of (E)-poly(1p-Si1) was 6 nm more red-shifted than
that of (Z)-poly(1p-Si1). Furthermore, the absorption edge of (E)-
poly(1p-Si1) was positioned at a wavelength approximately 30 nm
longer than that of (Z)-poly(1p-Si1). In fact, the THF solution of (E)-
poly(1p-Si1) was more yellowish than that of (Z)-poly(1p-Si1) as
shown in Fig. 2. It is considered that (E)-vinylene-linkage enhances
the conjugation more largely than the (Z)-counterpart.
Fig. 3 depicts the UVevis spectra of model compounds (chem-
ical structures are also shown) of (E)- and (Z)-polymers, simulated
by the DFT (B3LYP/6-31G*) calculation [16]. The predicted spectra
well agrees with the longer conjugation of the (E)-vinylene-con-
taining polymer than that of (Z)-polymer.
Fig. 4 shows the fluorescence spectra of the obtained polymers
together with those of diynes 1p and 1m. The emission peaks of 1p-
based polymers were broad compared with that of 1p, indicating
the delocalization and conjugation extension [17]. On the other
hand, 1m-based polymers emitted fluorescence with almost the
same pattern as that of 1m, indicating the slight extension of
conjugation. These results support the conclusion that 1p-based
polymers have conjugation lengths longer than those of 1m-based
polymers. In addition, the emission peak of (E)-poly(1p-Si1) was
broad compared with that of (Z)-poly(1p-Si1). It is suggested that
the conjugation length of the (E)-polymer is longer than that of the
(Z)-polymer. These trends agree with the results of UVevis spec-
troscopy. The fluorescence quantum yields of the polymers ranged
from 0.04 to 0.48. Among them, (E)-poly(1p-Si1) and (Z)-poly(1p-
Si1) clearly emitted florescence as shown in the picture in Fig. 5.
The CD spectra of the polymers were also measured in THF/H2O and
THF/hexane mixtures with various compositions (1/9e9/1, v/v), but
no signal was observed. There was no evidence for the polymers to
adopt chiral higher-order structures such as helix.
before hydrolysis. The [
5e10ꢂ larger in the minus direction than those before hydrolysis,
while the [
D values of 1m-based E-polymers became 3e10ꢂ larger
in the plus direction than those before hydrolysis. The absolute [
a]D values of 1p-based E-polymers became
a]
a
]
D
values of the all hydrolyzed polymers were not so large (less than
14ꢂ) similar to those of non-hydrolyzed polymers (less than 10ꢂ).
Table 3 summarizes the solubility of the polymers before and
after hydrolysis. The (E)-polymers tended to become insoluble or
poorly soluble in toluene, CH2Cl2, and CHCl3 after hydrolysis as
predicted from the hydrophilic feature of carboxy group. On the
other hand, the (Z)-polymer exhibited the same solubility in the
solvents listed in Table 3 before and after hydrolysis. It is presumed
that the hydrolyzed (Z)-polymer positions the carboxy groups at
the inner space of the polymer chain to shield the hydrophilic part
from solvents. As a result, it is soluble in hydrophobic solvents like
toluene, CH2Cl2, and CHCl3.
Figs. 6 and 7 show the UVevis and fluorescence spectra of the
polymers before and after hydrolysis. The shapes and intensities
slightly changed upon hydrolysis. It is considered that the substit-
uents affected the way of conjugation of the polymer main chain to
some extent. The CD spectra of the hydrolyzed polymers were also
measured in THF/H2O and THF/hexane mixtures with various
compositions (1/9e9/1, v/v), but no signal was observed unfortu-
nately. It seems that the silylene linkage is not enough rigid for the
polymers to adopt chiral higher-order structures such as helix.
Table 3
Solubility of the polymers.a
Polymer
Hexane
Toluene
CHCl3
CH2Cl2
THF
MeOH
DMF
DMSO
0.1 M NaOH aq.
(E)-poly(1peSi1)
(E)-poly(1peSi1)-hydrolyzed
(E)-poly(1peSi2)
(E)-poly(1peSi2)-hydrolyzed
(E)-poly(1meSi1)
(E)-poly(1meSi1)-hydrolyzed
(E)-poly(1meSi2)
(E)-poly(1meSi2)-hydrolyzed
(Z)-poly(1peSi1)
(Z)-poly(1peSi1)-hydrolyzed
e
e
e
e
e
e
e
e
e
e
þ
e
þ
e
þ
e
þ
e
þ
þ
þ
ꢃ
þ
e
þ
e
þ
e
þ
þ
þ
e
þ
e
þ
e
þ
e
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
e
e
e
e
e
e
e
e
e
e
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
ꢃ
ꢃ
e
e
e
e
e
e
e
e
a
Symbols: þsoluble, ꢃpartly soluble, einsoluble.

T. Ueda et al. / Polymer 52 (2011) 3570e3579
3577
ester moieties. Some of the polymers exhibited two fluorescent
emission peaks. The peaks at shorter wavelengths are assignable to
the emission from the diyne units, because the positions almost
agree with those of the diynes (377 and 369 nm). The emission
peaks at longer wavelengths should come from the conjugated
polymer backbones.
Fig. 8 shows the cyclic voltammograms of (E)-poly(1p-Si1) and
(Z)-poly(1p-Si1). Regardless of the different geometric structures of
the polymers, almost the same shaped voltammograms were
Fig. 6. UVevis spectra of the polymers before and after hydrolysis measured in THF
(6.77e7.59 ꢁ 10ꢀ6 M).
Table 4 summarizes the UVevis absorption and fluorescence
spectroscopic data of the polymers before and after hydrolysis
together with those of 1p and 1m. The fluorescence quantum yields
(F
’s) of the polymers were lower than those of the diynes, but
enough high as photoluminescence materials regarding the 1p-
based polymers. The low ’s of 1m-based polymers seem to be
F
related with the lower conjugation. Intersystem crossing may be
also the reason because the 1m-based polymers are more kinked
than the 1p-based ones. No significant difference of
observed between the polymers before and after hydrolysis of the
F’s was
Fig. 7. Fluorescence spectra (excited at the lmax wavelength) of the polymers
measured in THF (c ¼ 6.77e7.59 ꢁ 10ꢀ7 M).

3578
T. Ueda et al. / Polymer 52 (2011) 3570e3579
Table 4
4. Conclusion
UVevis absorption and fluorescence spectroscopic data of 1p, 1m, and the polymers.
a(cmꢀ1 Mꢀ1
)
emission
Fc
In this paper, we have demonstrated the hydrosilylation poly-
merization of hydroxyphenylglycine-derived diynes 1p and 1m with
dihydrosilanes Si1 and Si2 using RhI(PPh3)3 as a catalyst [21]. (E)-
Stereoregular polymers were obtained in good yields by feeding
a diyne, a dihydrosilane and the catalyst simultaneously. On the other
hand, (Z)-rich polymers were obtained by mixing a disilane and
a smaller amount of catalyst prior to the addition of a diyne. UVevis
and fluorescence spectroscopies revealed that the conjugation
lengths of the (E)-polymers were extended more than those of the
(Z)-counterparts, and those of the polymers containing p-phenylene
linkages were longer than those of the polymers containing no p-
phenylene linkages, which were supported by the DFT calculation of
the model compounds. The (E)-polymers tended to become insoluble
or poorly soluble in hydrophobic solvents after hydrolysis of the ester
groups as predicted from the hydrophilic feature of resulting carboxy
groups. Meanwhile, the (Z)-polymer did not obey this trend
presumably because the arrangement of the carboxy groups at the
inner space of the polymer chain, leading to shielding the hydrophilic
part from solvents. There was no different before and after hydrolysis
of ester moieties of polymers in spectroscopic properties. Unfortu-
nately, we could not observe the evidence for formation of higher-
order structures of the present polymers. It is concluded that the
Compound
UVevis
lmax (nm)
3
a
lmaxb(nm)
1p
1m
306
287
318
310
320
320
271
73,300
52,900
60,000
62,900
65,900
58,400
68,500
66,300
63,900
59,000
55,900
47,800
377 0.87
369 0.26
(E)-poly(1peSi1)
(E)-poly(1peSi1)-hydrolyzed
(E)-poly(1peSi2)
(E)-poly(1peSi2)-hydrolyzed
(E)-poly(1meSi1)
(E)-poly(1meSi1)-hydrolyzed 271
(E)-poly(1meSi2) 277
(E)-poly(1meSi2)-hydrolyzed 277
408 (381) 0.48
408 (382) 0.51
407 (383) 0.43
405 (384) 0.49
369 0.04
370 0.10
370 (382) 0.09
383 (373) 0.09
381 0.46
(Z)-poly(1peSi1)
(Z)-poly(1peSi1)-hydrolyzed
312
311
382 0.53
a
Measured in THF (c ¼ 6.44e7.59 ꢁ 10ꢀ6 M).
b
Measured in THF (c ¼ 5.89e7.59 ꢁ 10ꢀ7 M). Excited at the wavelength of lmax of
the UVevis absorption. Parentheses: emission wavelength of the second maximum.
c
Photoluminescence quantum yield determined using anthracene as a standard.
observed. Since oxidation peaks were not clearly detected, the
HOMO energy levels could not be calculated electrochemically. The
LUMO levels of (E)-poly(1p-Si1) and (Z)-poly(1p-Si1) were esti-
mated to be ꢀ4.98 and ꢀ4.97 eV, respectively [20].
sep
conjugated silylenevinylene units are not enough rigid for the
present polymers to adopt higher-order structures. Further studies
on the synthesis of
D
-(ꢀ)-p-hydroxyphenylglycine-derived chirally
ordered conjugated polymers are under progress.
Acknowledgment
This research was partly supported by a Grant-in-Aid for Science
Research (B) (22350049) from the Ministry of Education, Culture,
Sports, Science, and Technology, Japan and The Kurata Memorial
Hitachi Science and Technology Foundation. We are grateful to Dr.
Fumiaki Iwasaki at Tokuyama Corporation and Mr. Motoo Fukush-
ima at Shin-Etsu Chemical Co., Ltd. for donating reagents.
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