Living anionic polymerization of styrene derivatives containing triphenylamine moieties through introduction of protecting group

Article abstract of DOI:10.1021/ma1014353

We carried out the anionic polymerization of styrene derivatives containing the triphenylamine moieties, 4,4-vinylphenyltriphenylamine (A) and 4,4-vinylphenyl-N,N-bis(4-tert-butylphenyl)benzenamine (B), with a variety of initiators in tetrahydrofuran (THF

Full text of DOI:10.1021/ma1014353

8400 Macromolecules 2010, 43, 8400–8408
DOI: 10.1021/ma1014353
Living Anionic Polymerization of Styrene Derivatives Containing
Triphenylamine Moieties through Introduction of Protecting Group
Beom-Goo Kang, Nam-Goo Kang, and Jae-Suk Lee*
Department of Nanobio Materials and Electronics and School of Materials Science and Engineering,
Gwangju Institute of Science and Technology (GIST), 1 Oryong-dong, Buk-gu, Gwangju 500-712, Korea
Received June 28, 2010; Revised Manuscript Received September 6, 2010
ABSTRACT: We carried out the anionic polymerization of styrene derivatives containing the triphenyl-
amine moieties, 4,40-vinylphenyltriphenylamine (A) and 4,40-vinylphenyl-N,N-bis(4-tert-butylphenyl)-
benzenamine (B), with a variety of initiators in tetrahydrofuran (THF) at -78 °C. The anionic polymerization
of A was performed with sec-butyllithium, sec-butyllithium with additives, and (diphenylmethyl)potassium in
THF at -78 °C. In all cases, an intermolecular side reaction took place between the polymer chains during
polymerization. In contrast, the anionic polymerization of B was carried out successfully with sec-
butyllithium and potassium naphthalenide in THF at -78 °C for 0.5 h without any observed intermolecular
side reaction. Well-defined poly(B)s with predictable molecular weights and narrow molecular weight
distributions (Mw/Mn = 1.05-1.11) were obtained. The sequential block copolymerization of B with styrene
and 2-vinylpyridine was attempted subsequently, and the well-defined block copolymers, polystyrene-b-
poly(B) and poly(B)-b-poly(2-vinylpyridine), were synthesized quantitatively. The solubilities as well as the
thermal and optical properties of the resulting poly(B) were investigated.
Introduction
under different anionic conditions.16,17 However, it was con-
firmed from polymerization results that the polymerization was
Polymers containing triphenylamine and its derivatives have
received significant attention in numerous applications of organic
electronic devices, such as organic light-emitting diodes (OLEDs)
and photovoltaic cells, because they are materials that have an
excellent ability to transport and inject hole.1-5 In recent years,
side-chain polymers with triphenylamine moieties and polymeric
hole-transporting materials, in which the triphenylaminemoieties
are incorporated in the main chain, have attracted much interest
because they are highly thermally stable and are suitable for low-
cost fabrication processes such as spin-coating and inkjet printing
for large areas and flexible displays.6-13
To date, a variety of polymerization methods have been used
to prepare side-chain polymers containing triphenylamine moieties.
The methods include anionic,14-19 free or living radical,9,20-26 and
ring-opening methathesis polymerization.27-29 Among these
polymerization methods, anionic polymerization is the best
methodology to synthesize polymers with predictable molecular
weights and narrow molecular weight distributions (MWDs).
Additionally, the well-controlled block copolymers with precise
molecular architectures such as star-shaped, graft, comblike, and
cyclic-shaped polymers can be prepared through this polyme-
rization method.30-35 Many polymeric hole-transporting materials,
in which triphenylamine moieties are introduced in the side chain,
have been studied widely by anionic polymerization.
not controlled because the undesirable side reaction occurred in
both polymerization systems.
During the past 2 years, there have been two advanced reports
on the living anionic polymerization of 4-vinyltriphenylamine.
The anionic polymerization of 4-vinyltriphenylamine was at-
tempted by Natori et al. in toluene at 25 °C under dry argon
using the initiator system of tert-butyllithium/N,N,N0,N0-tetra-
methylethylenediamine (TMEDA) (Chart 1a).18 In the presence
of TMEDA, the proton removal resulting from the reaction of
toluene and tert-butyllithium produced tolyllithium, which was
the real initiator in the polymerization. They could prepare high
molecular weight polymers (∼56 K), but the MWDs were rela-
tively broad (Mw/Mn = 1.10-1.27), and it took 24 h to complete
the polymerization with 100% yield. Very recently, Higashihara
et al. achieved living anionic polymerization of 4-vinyltriphenyl-
amine with sec-butyllithium in tert-butylbenzene at 25 °C for
24 h or with sec-butyllithium and lithium naphthalenide in THF
at -78 °C for 12 h without any additives (Chart 1b).19 The
resulting poly(4-vinyltriphenylamine) with predictable high
molecular weights (∼30K) and narrow MWDs (Mw/Mn
=
1.04-1.10) was synthesized quantitatively.
In our group, we have been studying the living anionic poly-
merization and block copolymerization of isocyanate, methacry-
late, and styrene derivatives with various functional groups and
established their anionic polymerization behaviors.36,37 In parti-
cular, we have reported that methacrylate and styrene derivatives
containing carbazole moieties, which show good hole-transport-
ing properties, successfully undergo living anionic polymeriza-
tion by controlling polymerization conditions such as time,
initiator, and temperature.37
Se et al. carried out a living anionic polymerization of
N,N-dimethyl-4-vinylphenylamine using cumylpotassium as an
initiator in tetrahydrofuran (THF) at -78 °C under high-vacuum
conditions (10-6 Torr).14 They reported that the well-defined
poly(N,N-dimethyl-4-vinylphenylamine) with high molecular
weights (<260 K) and narrow MWDs, which were less than
1.10, has been obtained. Feast et al. and Tew et al. have tried to
perform the anionic polymerization of 4-vinyltriphenylamine
In this study, we have synthesized functional styrene deriva-
tives containing triphenylamine moieties, 4,40-vinylphenyltriphenyl-
amine (A) and 4,40-vinylphenyl-N,N-bis(4-tert-butylphenyl)-
benzenamine (B), because triphenylamine derivatives show good
*Corresponding author: Tel þ82-62-715-2306; Fax þ82-62-715-2304;
e-mail jslee@gist.ac.kr.
pubs.acs.org/Macromolecules
Published on Web 09/21/2010
r 2010 American Chemical Society

Article
Macromolecules, Vol. 43, No. 20, 2010 8401
Chart 1. Summary of Anionic Polymerization of (a, b) 4-Vinyltriphe-
nylamine and (c) 4,40-Vinylphenyltriphenylamine and 4,40-Vinylphenyl-
N,N-bis(4-tert-butylphenyl)benzenamine
containing 2% triethylamine as the eluent at 40 °C and calibrated
withpolystyrene standards (American Polymer Standards Corp.).
Thermal properties were characterized using thermogravimetric
analysis (TGA, TA2050) and differential scanning calorimetry
(DSC, TA2010) at a heating rate of 10 °C/min under nitrogen.
UV-vis absorption and photoluminescence (PL) spectra were
obtained using an Agilent 8453 UV-vis spectrophotometer and a
Hitachi F-7000 fluorescence spectophotometer, respectively.
Initiators. (Diphenylmethyl)potassium (Ph2CHK) was syn-
thesized by the reaction of potassium naphthalenide (K-Naph)
and a 1.5 M excess of diphenylmethane in dry THF at 25 °C
for 3 days. Commercially available sec-butyllithium (sec-BuLi,
1.0 M in cyclohexane, Kanto Chemical Co., Inc.) was used
without purification and was diluted with dry n-heptane. The
diluted Ph2CHK and sec-BuLi solutions were stored at -30 °C
in ampules equipped with break-seals prior to anionic poly-
merization. The efficiency of initiators was determined by
titration with octyl alcohol in a sealed reactor under vacuum.
4,40-Vinylphenyltriphenylamine (A). 4-Bromotriphenylamine
(8.40 g, 26.0 mmol), 4-vinylphenylboronic acid (5.00 g, 33.8
mmol), and tetrakis(triphenylphosphine)palladium(0) (1.10 g)
were stirred in 100 mL of THF. After adding 30 mL of aqueous
2 M K2CO3, the reaction mixture was reacted at 80 °C for 24 h
(Scheme 1). The crude mixture was cooled to ambient tempera-
ture. The solvent was removed by evaporation under reduced
pressure, and the reaction mixture was poured into water and
extracted with methylene chloride three times. The combined
organic solution was dried over anhydrous Na2SO4 and filtered.
After evaporation of the solvent, the residue was purified by
silica column chromatography with n-hexane and methylene
chloride (9.5:0.5) to give a white solid (7.20 g, 20.7 mmol, 80%,
hole-transporting properties, and it has been reported that
hole-transporting materials with high glass transition tempera-
tures (Tgs) improve the thermal and long-term stability necessary
for high efficiency of organic EL devices.38 Therefore, it is
expected that poly(A) and poly(B), which possess structurally
bulky and rigid moieties, may show higher Tgs and better hole-
transporting properties than those of poly(4-vinyltriphenyl-
amine). Particularly, their anionic polymerization behaviors,
strongly influenced by the introduction of a protecting tert-
butyl group to the triphenylamine moiety, are mainly descri-
bed in this paper (Chart 1c). Furthermore, the block co-
polymerization of B with styrene and 2-vinylpyridine was
carried out to investigate the nucleophilicity of living poly(B)
and its living nature.
1
mp = 119 °C). H NMR (400 MHz, CDCl3): δ = 5.24-5.27
(d, 1H, CH2= trans, J = 11.0 Hz), 5.75-5.80 (d, 1H, CH2= cis,
J = 17.6 Hz), 6.71-6.78 (dd, 1H, =CH trans, J = 11.0 and 17.6
Hz), 7.03-7.55 (m, 18H, aromatic). 13C NMR (100 MHz,
CDCl3): δ = 113.6 (CH2=), 123.0, 123.8, 124.4, 126.6, 126.7,
127.6, 129.3, 134.5, 136.1, 136.4 (=CH), 140.0, 147.2, 147.6.
FT-IR (KBr, cm-1): 3038, 1592, 1526, 1488, 1333, 1279, 990,
908, 826, 748. Anal. Calcd for C26H21N: C, 89.88; H, 6.09;
N, 4.03. Found: C, 90.03; H, 5.89; N, 4.08. MS (EI): m/z
347.05 (Mþ).
N,N-Bis(4-tert-butylphenyl)-4-bromobenzenamine. To a stirred
solution of bis(4-tert-butylphenyl)amine (10.0 g, 35.5 mmol),
1-bromo-4-iodobenzene (15.1 g, 53.3 mmol), and potassium
carbonate (20.0 g, 145 mmol) in 1,2-dichlorobenzene (200 mL)
under nitrogen was added copper powder (10.2 g, 160 mmol), and
the reaction mixture was stirred continuously at 190 °C for 24 h
(Scheme 1). The crude mixture was cooled to ambient tempera-
ture and filtered to remove inorganic solids. The combined
organic phase was poured into water and extracted with methy-
lene chloride three times. The organic solution was dried over
anhydrous Na2SO4 and filtered. After removal of the solvent, the
residue was purified by silica column chromatography with n-
hexane to give a white solid (8.20 g, 18.8 mmol, 53%). 1H NMR
(400 MHz, CDCl3): δ = 1.31 (s, 18H, tert-butyl), 6.90-7.30
(m, 12H, aromatic). 13C NMR (100 MHz, CDCl3): δ = 31.4
(C(CH3)3), 34.3 (C(CH3)3), 113.7, 124.0, 124.3, 126.1, 131.9,
144.6, 146.1, 147.3. MS (EI): m/z 435.75 (Mþ).
Experimental Section
Materials. 4-Bromotriphenylamine (97%), 1-bromo-4-iodo-
benzene (98%), 1,2-dichlorobenzene (99%), copper powder (99%),
4-vinylphenylboronic acid, and tetrakis(triphenylphosphine)-
palladium(0) (99%) were purchased from Aldrich Chemical Co.
and used without further purification. Bis(4-tert-butylphenyl)-
amine (>90%) was supplied from Tokyo Chemical Industry
Co. Ltd. and was purified by repeated recrystallization from
ethanol. Styrene (St), 2-vinylpyridine (2VP), and R-methylstyrene
(R-MeSt) were passed through an alumina column, washed with
an aqueous 5% sodium hydroxide (NaOH) solution, and then
dried over anhydrous sodium sulfate (Na2SO4) for 24 h. These
were distilled from calcium hydride (CaH2) under vacuum and
then further distilled from CaH2 on a vacuum line. Lithium
chloride (LiCl) was dried for 24 h at 150 °C under vacuum. All of
the monomers and additives were diluted with tetrahydrofuran
(THF) and divided in ampules with break-seals on a vacuum
line. THF used in the polymerization reactions was refluxed
over sodium for 5 h and then distilled on a vacuum line from a
sodium naphthalenide solution.
1
Measurements. H and 13C NMR spectra were recorded at
25 °C using CDCl3 as a solvent (JEOL JNM-ECX400). Chemical
shifts were referred to tetramethylsilane (TMS) at 0 ppm. FT-IR
spectroscopy was carried out from 4000 to 400 cm-1 using KBr
pellets (Perkins-Elmer Spectrum 2000). Elemental analyses were
performed by the Seoul Branch Analytical Laboratory of the
Korea Basic Science Institute (Flash EA 1112series, CE In-
struments). Mass values were detected by a gas chromatograph
mass spectrometer (GCMS, Shimadzu, GCMS-QP2010). The
polymers were characterized by size exclusion chromatography
(SEC, Waters M 77251, M510). Molecular weights of the poly-
mers were measured by SEC with four columns (HR 0.5, HR 1,
HR 3, and HR 4, Waters Styragel columns run in series; the pore
4,40-Vinylphenyl-N,N-bis(4-tert-butylphenyl)benzenamine (B).
The same procedure was followed, as described above for A,
using N,N-bis(4-tert-butylphenyl)-4-bromobenzenamine (8.00 g,
18.3 mmol), 4-vinylphenylboronic acid (4.10 g, 27.5 mmol),
tetrakis(triphenylphosphine)palladium(0) (1.00 g), THF (120 mL),
and aqueous 2 M K2CO3 (40 mL). The coupling reaction was
continued at 80 °C for 24 h under a nitrogen atmosphere
(Scheme 1). The residue was purified by silica column chromatog-
raphy with n-hexane and methylene chloride (9.5:0.5) to give a
1
white solid (5.10 g, 11.1 mmol, 61%, mp = 195 °C). H NMR
3
4
˚
size of the columns is 50, 100, 10 , and 10 A, respectively) with a
refractive index detector at a flow rate of 1.0 mL/min using THF
(400 MHz, CDCl3): δ = 1.31 (s, 18H, tert-butyl), 5.23-5.26 (d,
1H, CH2= trans, J = 11.0 Hz), 5.74-5.79 (d, 1H, CH2= cis,

8402 Macromolecules, Vol. 43, No. 20, 2010
Kang et al.
Scheme 1. Synthesis of 4,40-Vinylphenyltriphenylamine (A) and 4,40-Vinylphenyl-N,N-bis(4-tert-butylphenyl)benzenamine (B)
Table 1. Anionic Polymerization of 4,40-Vinylphenyltriphenylamine (A) and 4,40-Vinylphenyl-N,N-bis(4-tert-butylphenyl)benzenamine (B)
in Tetrahydrofuran at Various Temperatures
Mn ꢀ 10-3
b
run
monomer (mmol)
initiator type (mmol)
sec-BuLi, 0.0142
sec-BuLi, 0.0112
temp (°C)
time (h)
calcda
obsdb
Mw/Mn
yield (%)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
A, 1.10
A, 0.741
A, 2.23
A, 2.05
A, 1.23
A, 2.14
B, 0.722
B, 1.15
B, 0.623
B, 1.13
B, 1.94
B, 1.03
B, 0.558
B, 1.04
B, 0.465
-78
-78
-78
-78
-78
-78
-78
-78
-78
-78
-78
-78
-78
25
5 min
0.5
1
1
1
1
0.5
0.5
0.5
0.5
0.5
0.5
19.0
23.0
7.8
14.0
7.1
22.3
4.7
14.4
6.4
16.2
23.1
29.5
12.0
14.7
6.7
21.4
29.2
6.2
16.1
9.8
21.6
4.8
14.1
6.2
16.3
23.3
30.0
13.2
14.3
6.9
g
g
g
g
g
g
1.05
1.11
1.10
1.09
1.06
1.09
1.06
g
70.6
100
100
100
100
100
100
100
100
100
100
100
73.9
100
100
sec-BuLi, 0.0995
sec-BuLi, 0.0541/R-MeSt,c 0.370
sec-BuLi, 0.0601/LiCl,d 0.0609
Ph2CHK,e 0.0334
sec-BuLi, 0.0701
sec-BuLi, 0.0368
K-Naph,f 0.0895
K-Naph, 0.0642
K-Naph, 0.0771
K-Naph, 0.0321
K-Naph, 0.0317
K-Naph, 0.0650
K-Naph, 0.0638
10 min
10 min
10 min
0
g
aMn(calcd) = (molecular weight of monomer) ꢀ [monomer] ꢀ f/[initiator]; f = 1 or 2, corresponding to the functionality of the initiators. bMn(obsd)
and Mw/Mn were gained by size exclusion chromatography calibration by using polystyrene standards in tetrahydrofuran solution containing 2%
triethylamine as the eluent at 40 °C. cR-Methylstyrene. d Lithium chloride. e(Diphenylmethyl)potassium. f Potassium naphthalenide. g The Mw/Mn was
bimodal, presumably due to the intermolecular side reaction.
Table 2. Block Copolymerization of 4,40-Vinylphenyl-N,N-bis(4-tert-butylphenyl)benzenamine (B) with Styrene (St) and 2-Vinylpyridine (2VP)
with sec-BuLi in Tetrahydrofuran at -78 °Ca
block copolymer (homopolymer)
monomer
Mn ꢀ 10-3
calcdb
obsdc
f (5.0)
22.7 (13.2)
29.7 (12.0)
Mw/Mn
f (1.07)
c
run
initiator, mmol
1st, mmol
2nd, mmol
1
2
3
sec-BuLi, 0.0699
sec-BuLi, 0.0251
sec-BuLi, 0.0461
B, 0.763
St, 2.94
B, 1.19
St,d 3.05
B, 0.601
10.0 (5.0)
24.4 (12.2)
28.3 (11.8)
1.09 (1.13)
1.08 (1.11)
2VP,e 5.90
aPolymer yields were quantitative in all cases. Polymerization times were total 1 h, 0.5 h for B, and 0.5 h for St and 2VP. bMn(calcd) = (molecular
weight of monomer) ꢀ [monomer]/[initiator]. cMn(obsd) and Mw/Mn were gained by size exclusion chromatography calibration by using polystyrene
standards in tetrahydrofuran solution containing 2% triethylamine as the eluent at 40 °C. dStyrene. e2-Vinylpyridine. f The initiation efficiency was not
quantitative, forming a mixture of homopolymer and resulting block copolymer.
J = 17.6 Hz), 6.70-6.77 (dd, 1H, =CH trans, J = 11.0 and 17.6
Hz), 7.04-7.54 (m, 16H, aromatic). 13C NMR (100 MHz, CDCl3):
δ = 31.4 (C(CH3)3), 34.3 (C(CH3)3), 113.4 (CH2=), 122.9, 124.1,
126.1, 126.5, 126.6, 127.4, 133.7, 135.9, 136.5 (=CH), 140.2, 144.9,
145.8, 147.6. FT-IR (KBr, cm-1): 3034-2871, 1598, 1506, 1497,
1364, 1324, 1299, 985, 879, 827, 741. Anal. Calcd for C34H37N: C,
88.84; H, 8.11; N, 3.05. Found: C, 88.69; H, 8.26; N, 2.96. MS (EI):
m/z 459.20 (Mþ).
Purification of Monomers. After silica column chromatogra-
phy of A and B, the monomers were freeze-dried from their
benzene solutions under reduced pressure for 12 h and then
dried over phosphorus(V) oxide (P2O5) at 25 °C for 24 h in an
glass apparatus equipped with break-seals on a vacuum line.
The resulting monomers were diluted with dry THF and stored
at -30 °C in glass ampules under high vacuum prior to anionic
polymerization.

Article
Anionic Polymerization of A. The anionic polymerization of A
Macromolecules, Vol. 43, No. 20, 2010 8403
Anionic Polymerization of B. The same polymerization pro-
cedure was followed, as described above for anionic polymeri-
zation of A, using sec-BuLi and K-Naph in THF at -78 °C for
0.5 h. The color of polymerization solution was deep violet. The
resulting polymer was characterized by 1H NMR, SEC, ele-
mental analysis (EA), and FT-IR spectroscopy with the follow-
ing results. Poly(B) (Mn(obsd) = 30 000, Mw/Mn = 1.09 (Table 1,
was carried out with sec-BuLi, sec-BuLi with some additives,
and Ph2CHK in THF at -78 °C under high vacuum (10-6 Torr)
in all-glass reactors equipped with break-seals. The additives
included R-MeSt and LiCl. The reactor was prewashed with the
initiator solution after sealing from the vacuum line. The poly-
merization was usually performed by addition of monomer into
the initiator solution. The reaction mixture immediately turned to
deep violet after A was added to the initiator solution. The
polymerization was terminated with methanol, and the reaction
solution was poured into a large excess of methanol to precipitate
the polymer. The polymer was purified by reprecipitationinTHF/
methanol and freeze-dried from a benzene solution under
vacuum. The polymers were characterized by SEC.
1
run 12)). H NMR (400 MHz, CDCl3): δ = 1.23 (18H, tert-
butyl), 1.32-2.30 (3H, CH2-CH), 6.45-7.46 (16H, aromatic).
FT-IR (KBr, cm-1): 3033-2868, 1602, 1511, 1496, 1365, 1322,
1296, 1190, 1112, 1015, 822, 746. Anal. Calcd for (C34H37N)n: C,
88.84; H, 8.11; N, 3.05. Found: C, 87.89; H, 8.03; N, 2.84.
Block Copolymerization. The first-stage polymerization of
St was performed with sec-BuLi in THF at -78 °C for 0.5 h in
an all-glass apparatus equipped with break-seals under high
vacuum (10-6 Torr). After a portion of the living poly(St) was
sampled to characterize the poly(St), B was poured into the
living poly(St) solution and the mixture reacted at -78 °C for
0.5 h. After termination with methanol, the reaction solutions
were poured into a large excess of methanol to obtain both
poly(St) and poly(St)-b-poly(B). The block copolymerization of
B with 2VP was carried out by addition of 2VP into living
poly(B) solution at -78 °C for 0.5 h. The resulting block
1
polymers were characterized by means of H NMR and SEC
with the following results. Poly(St)-b-poly(B) (Mn(obsd) =
22 700, Mw/Mn = 1.09 (Table 2, run 2)). 1H NMR (400 MHz,
CDCl3): δ = 1.05-2.25 (CH2-CH of poly(St) and poly(B), tert-
butyl of poly(B)), 6.25-7.38 (phenyl of poly(St) and triphenyl-
amine of poly(B)). Poly(B)-b-poly(2VP) (Mn(obsd) = 29 700,
Mw/Mn = 1.08 (Table 2, run 3)). 1H NMR (400 MHz, CDCl3):
δ = 1.19 (tert-butyl of poly(B)), 1.30-2.11 (CH2-CH of poly-
(B) and poly(2VP)), 2.15-2.40 (CH2-CH of poly(2VP)),
6.10-7.25 (triphenylamine of poly(B) and pyridine of poly-
(2VP)), 8.08-8.35 (CHdN of poly(2VP)).
Results and Discussion
Figure 1. SEC curves of (a) poly(4,40-vinylphenyltriphenylamine) pre-
pared with sec-BuLi at -78 °C for 5 min (Table 1, run 1), (b) poly(4,40-
vinylphenyltriphenylamine) prepared with sec-BuLi at -78 °C for 0.5 h
(Table 1, run 2), (c) poly(4,40-vinylphenyl-N,N-bis(4-tert-butylphenyl)-
benzenamine) prepared with sec-BuLi at -78 °C for 0.5 h (Table 1, run 8),
Mn(obsd) = 14 100 and Mw/Mn = 1.11, and (d) poly(4,40-vinylphenyl-N,
N-bis(4-tert-butylphenyl)benzenamine) prepared with K-Naph at -78 °C
for 0.5 h (Table 1, run 10), Mn(obsd) = 16 300 and Mw/Mn = 1.09.
Anionic Polymerization of A. The results of the anionic
polymerization of A are summarized in Table 1. First, the
polymerization of A was carried out with sec-BuLi for 0.5 h.
The yield of the polymer was quantitative, but the size
exclusion chromatography (SEC) curve of the resulting
polymer showed a bimodal peak and the molecular weight
distribution (MWD) was relatively broad, as shown in Figure 1b.
Scheme 2. Proposed Anionic Polymerization Behaviors of (a) 4,40-Vinylphenyltriphenylamine and (b) 4,40-Vinylphenyl-N,N-bis(4-tert-
butylphenyl)benzenamine

8404 Macromolecules, Vol. 43, No. 20, 2010
Kang et al.
In the SEC curve, there was a shoulder in the higher Mn
region that matched well with the double Mn of the main
peak. For the 5 min reaction time, the results from SEC curve
(Figure 1a) were identical with those of the polymerization
performed for 0.5 h, although the polymer yield was 70.6%.
Next, additives (R-MeSt and LiCl), introduced to lower the
reactivity of sec-BuLi, and Ph2CHK were used to synthesize
the well-defined poly(A) with predictable molecular weight
and narrow MWD. In all cases, however, the analysis of SEC
curve showed identical results to that of the polymerization
using sec-BuLi, even though the resulting polymer was
obtained quantitatively.
These results suggest that the intermolecular side reaction
probably took place between the polymer chains during the
course of the polymerization of A under the conditions
employed here, as shown in Scheme 2a.39 Accordingly, this
undesirable side reaction, which does not occur in the anionic
polymerization of 4-vinyltriphenylamine in THF at -78 °C
for 12 h with sec-BuLi,19 may support that electron-with-
drawing nature, possibly indicated by the chemical shifts of
the vinyl β-carbon in their 13C NMR spectra of 4-vinyl-
triphenylamine (112.4 ppm)17 and A (113.6 ppm), greatly
affects their anionic polymerization behaviors.40
Living Anionic Polymerization of B. In the previous study,
it was found that the living anionic polymerization of A was
not successful when carried out at -78 °C due to the
intermolecular side reaction. Thus, monomer B was pre-
pared for the protection against the unwanted intermolec-
ular side reaction. In monomer B, the site (Scheme 2a)
attacked by the propagating chain-end carbanion at -78 °C
was protected by the introduction of a tert-butyl group. The
polymerization of B was carried out successfully with sec-
BuLi and K-Naph at -78 °C, and the results are summarized
in Table 1. The yields of polymers were always quantitative.
As shown in Figure 2, the 1H NMR spectrum of the mono-
mer and resulting polymer clearly shows that polymerization
proceeded exclusively because the signal of vinyl group of
monomer disappeared, and the broad signal of the main
polymer chain and the broad characteristic singlet of the tert-
butyl group (1.23 ppm) appeared. Therefore, the study of the
polymer using 1H NMR spectroscopy proves the success of
the anionic polymerization of B and the structure of poly(B).
As illustrated in Figure 1c,d, SEC measurements clearly
showed unimodal curves with narrow MWDs for the result-
ing poly(B)s. The MWDs of the resulting polymers, Mw/Mn
values, were around 1.10. Moreover, the observed Mn values
agreed well with calculated molecular weights based on
monomer-to-initiator ratios. These results mean that no
intermolecular side reaction took place during the polymer-
ization. For instance, the polymerization proceeded quanti-
tatively with sec-BuLi (Table 1, run 8). The molecular weight
(Mn = 14 100) detected from SEC was in good agreement
with the calculated molecular weight (14 400), and the
Mw/Mn ratio was 1.11. Thus, these results, as shown in
Table 1 and Figure 1c,d, indicate strongly that the anionic
polymerizations of B with sec-BuLi and K-Naph at -78 °C
proceed without intermolecular side reactions, suggesting
that the site attacked by propagating chain-end carbanion
corresponds with the one shown in Scheme 2a. In other
words, it is demonstrated that the nucleophilic attack of
propagating chain-end carbanion of the living poly(B) on
1
Figure 2. H NMR spectra of (a) 4,40-vinylphenyl-N,N-bis(4-tert-
butylphenyl)benzenamine and (b) poly(4,40-vinylphenyl-N,N-bis(4-
tert-butylphenyl)benzenamine) in CDCl3.
Figure 3. Plot of the feed ratio of 4,40-vinylphenyl-N,N-bis(4-tert-
butylphenyl)benzenamine to K-Naph vs Mn and Mw/Mn.
Figure 4. SEC curves of (a) poly(4,40-vinylphenyl-N,N-bis(4-tert-butylphenyl)benzenamine) prepared with K-Naph at 25 °C for 10 min (Table 1, run
14), (b) poly(4,40-vinylphenyl-N,N-bis(4-tert-butylphenyl)benzenamine) prepared with K-Naph at 0 °C for 10 min (Table 1, run 15), and (c) poly-
(4,40-vinylphenyl-N,N-bis(4-tert-butylphenyl)benzenamine) prepared with K-Naph at -78 °C for 10 min (Table 1, run 13): Mn(obsd) = 13200 and
Mw/Mn = 1.06.

Article
Macromolecules, Vol. 43, No. 20, 2010 8405
the triphenylamine moiety (para position) can be entirely
suppressed at -78 °C by the introduction of a tert-butyl
protecting group, as proposed in Scheme 2b.
In addition, poly(B)s were synthesized by using diverse
molar ratios of B to K-Naph to substantiate the living nature
of poly(B) (Table 1, runs 9-12). As shown in Figure 3, the
MWDs were less than 1.10, and the Mn values were increased
with increasing feed ratio of B to K-Naph. Such a good linear
relationship between Mn and the feed ratio of B to K-Naph
highlights the living nature of poly(B).
Effect of Polymerization Temperature. The anionic poly-
merization of B has been carried out with K-Naph in THF at
25, 0, and -78 °C for 10 min to investigate the temperature
dependence of the anionic polymerization. The polymeriza-
tion results are summarized in Table 1. The yields of poly-
mers were quantitative after termination. It was confirmed
from SEC analysis, however, that the resulting polymer
prepared at 25 °C showed a bimodal SEC curve with
relatively broad MWD, as shown in Figure 4a. There was a
shoulder at the high-Mn region with the main peak having a
narrow MWD. The observed Mn of the main peak agreed
fairly well with the calculated molecular weight, and the
double Mn of the main peak matched well with the peak in
the higher Mn region. These results are probably due to an
intermolecular side reaction between the polymer chains
after the polymerization. For the possible side reaction, we
now consider that the nucleophilic attack of propagating
chain-end carbanion of the living poly(B) on the triphenyl-
amine moiety (ortho position) might take place to some
extent,39 as shown in Scheme 3. This intermolecular side
reaction could not be suppressed completely at 0 °C, even
though the shape of the shoulder at the high-Mn region was
very small (Figure 4b). At -78 °C, the polymerization of B
was not complete within 10 min, and the yield of polymer was
73.9%. The SEC curve of the resulting polymer showed
unimodal shape with narrow MWD (Mw/Mn = 1.06), and
the observed Mn was in agreement with calculated molecular
weight based on monomer-to-initiator ratio, indicating that
there was no intermolecular side reaction. This result also
supports that the side reaction might occur not during
propagation but after the polymerization.41 The results
obtained here indicate that the polymerization temperature
should be -78 °C for controlled anionic polymerization of B.
Block Copolymerization of B with Styrene (St) and 2-Vi-
nylpyridine (2VP). From the synthetic viewpoint, the living
anionic polymerization by sequential addition of comono-
mers is one of the best methods to create block copolymer
because it offers a well-defined block copolymer with pre-
dictable molecular weight and narrow MWD. The results
summarized in Table 1 highlight the living character of B in
THF at -78 °C. Therefore, the achievement of the living
anionic polymerization of B enables the well-defined block
copolymer possessing poly(B) block to be produced by the
sequential block copolymerization. Additionally, the relative
reactivity of B and the terminal carbanion of the resulting living
Scheme 3. Proposed Anionic Polymerization Behavior of 4,40-
Vinylphenyl-N,N-bis(4-tert-butylphenyl)benzenamine with K-Naph
in Tetrahydrofuran at 25 and 0 °C
Figure 5. SEC curves of (a) poly(4,40-vinylphenyl-N,N-bis(4-tert-butylphenyl)benzenamine) (poly(B)) at the first-stage polymerization and copoly-
merization product at the second-stage polymerization with styrene (St) (Table 2, run 1): poly(B), Mn(obsd) = 5000 and Mw/Mn = 1.07, (b) poly-
(4,40-vinylphenyl-N,N-bis(4-tert-butylphenyl)benzenamine) at the first-stage polymerization and copolymerization product at the second-stage
polymerization with 2-vinylpyridine (2VP) (Table 2, run 3): poly(B), Mn(obsd) = 12 000 and Mw/Mn = 1.11; poly(B)-b-poly(2VP), Mn(obsd) =
29700 and Mw/Mn=1.08, and (c) reactivity order of 4,40-vinylphenyl-N,N-bis(4-tert-butylphenyl)benzenamine.

8406 Macromolecules, Vol. 43, No. 20, 2010
Kang et al.
Scheme 4. Block Copolymerization of 4,40-Vinylphenyl-N,N-bis(4-tert-butylphenyl)benzenamine with 2-Vinylpyridine in Tetrahydrofuran
at -78 °C with sec-BuLi
Table 3. Solubility of Poly(4,40-vinylphenyl-N,N-bis(4-tert-butylphenyl)-
benzenamine) (Poly(B))a
solvent
poly(B)
solvent
poly(B)
n-hexane
benzene
toluene
diethyl ether
ethyl acetate
chloroform
acetone
I
tetrahydrofuran
1,2-dichloroethane
1,2-dichlorobenzene
N,N-dimethylformamide
dimethyl sulfoxide
ethanol
S
S
S
I
I
I
S
S
S
S
S
I
methanol
water
I
I
1,4-dioxane
a Key: S, soluble; I, insoluble.
S
Figure 6. Thermogravimetric analysis (TGA) and differential scanning
calorimetry (DSC) thermograms of poly(4,40-vinylphenyl-N,N-bis(4-tert-
butylphenyl)benzenamine) (Mn = 30 000) under nitrogen with a heating
rate of 10 °C/min.
polymer can be provided by the results of the block copolymer-
zation. As shown in Table 2, two traditional comonomers,
styrene (St) and 2-vinylpyridine (2VP), were selected for the
block copolymerization to evaluate the reactivity of B.
The block copolymerization of St with B was carried out
successfully by sequential addition of St as the first monomer
and B as the second monomer. As listed in Table 2, the block
copolymer with predictable molecular weight and narrow
MWD was obtained quantitatively. The observed Mn values
of poly(St) and poly(St)-b-poly(B) detected from SEC were
13 200 (Mw/Mn=1.13) and 22 700 (Mw/Mn=1.09), respec-
tively, were similar to the calculated values of 12 200 and
24 400. The SEC curve of block copolymer was sharp and
symmetrical, and completely shifted from elution volume of
poly(St) toward higher Mn. This result means that the
propagating carbanion of St is stable at -78 °C for 0.5 h
and propagating chain end derived from St can certainly
polymerize B under the polymerization condition employed
here. In contrast, a well-defined block copolymer was not
synthesized by the reverse addition of two monomers. As
shown in Figure 5a, the SEC curve in the polymerization of
St with living poly(B) showed that the bimodal peak con-
sisted of poly(B) and the block copolymer possessing Mn
value much higher than predicted one because of partial
initiation with rapid consumption of St by the newly formed
polystyryl anion.41 This result suggests that living poly(B) is
not nucleophilic enough to polymerize St quantitatively,
meaning that living poly(B) cannot be used to prepare
well-defined block copolymers with St.
We were also able to synthesize the block copolymer,
poly(B)-b-poly(2VP), with sec-BuLi without any additives
(Scheme 4). The polymerization result is summarized in
Table 2. The well-defined block copolymer with controlled
molecular weight and narrow MWD was synthesized quan-
titatively. Figure 5b shows the SEC curves of poly(B) and
poly(B)-b-poly(2VP). The SEC curve of the resulting block
copolymer was unimodal and symmetrical and shifted from
the starting poly(B) toward the higher molecular side. Ac-
cordingly, it can be demonstrated that the polymerization of
2VP was carried out successfully by living poly(B) without
any side reaction. From the results of sequential block
Figure 7. Absorption (a) and photoluminescence (PL) (b) spectra of
4,40-vinylphenyl-N,N-bis(4-tert-butylphenyl)benzenamine and poly-
(4,40-vinylphenyl-N,N-bis(4-tert-butylphenyl)benzenamine) (4,40-vinyl-
phenyl-N,N-bis(4-tert-butylphenyl)benzenamine in toluene (0), poly-
(4,40-vinylphenyl-N,N-bis(4-tert-butylphenyl)benzenamine) in toluene
(O), and film of poly(4,40-vinylphenyl-N,N-bis(4-tert-butylphenyl)-
benzenamine) (Δ)).
copolymerization of B with St and 2VP, the reactivity of
living poly(B) was found to be between that of St and 2VP, as
shown in Figure 5c.
Solubility. The test of solubility of poly(B) was carried out
using the various organic solvents at 25 °C and is summarized in
Table 3. The polymer was soluble in benzene, toluene, diethyl

Article
Macromolecules, Vol. 43, No. 20, 2010 8407
Table 4. Photophysical Properties of 4,40-Vinylphenyl-N,N-bis-
the intermolecular side reaction was completely suppressed by the
introduction of the tert-butyl protecting group to the tripheny-
lamine moiety without any additives. The block copolymeriza-
tion of B with styrene and 2-vinylpyridine was performed
sequentially to estimate the reactivity of B and to find its living
nature. The well-defined polystyrene-b-poly(B) and poly(B)-b-
poly(2-vinylpyridine) with predictable molecular weights and
narrow MWDs were synthesized, and it was confirmed that
reactivity of living poly(B) was between that of styrene and
2-vinylpyridine. The poly(B) (Mn = 30 000) showed good solu-
bility and excellent thermal stability for potential applications in
electronic devices.
(4-tert-butylphenyl)benzenamine (B) and Poly(4,40-vinylphenyl-N,
N-bis(4-tert-butylphenyl)benzenamine) (Poly(B))
solutiona
film
UV-vis λmax
(nm)
PL λmax
(nm)
UV-vis
PL λmax
(nm)
material
λ
max (nm)
B
poly(B)
311, 352
332
415
395
314
412
a In toluene dilute solution.
ether, ethyl acetate, chloroform, 1,4-dioxane, tetrahydrofuran,
1,2-dichloroethane, and 1,2-dichlorobenzene. On the other
hand, it was not soluble in n-hexane, cyclohexane, acetone,
N,N-dimethylformamide, dimethyl sulfoxide, ethanol, metha-
nol, and water. Poly(B) was spin-coated successfully from
the toluene solution. Consequently, this thin film can be a
potential candidate for practical applications of organic
electronic devices.
Acknowledgment. This work was supported by the Program
for Integrated Molecular System (PIMS) and the World Class
University (WCU) Program (Project No. R31-20008-000-10026-0).
We thank the Korea Basic Science Institute (KBSI) for EA
measurements.
Thermal Properties. The thermal stability of poly(B) (Mn =
30 000) was investigated by thermogravimetric analysis (TGA)
under nitrogen. The TGA thermogram and the value of the
10% weight loss temperature (T10) of poly(B) are shown in
Figure 6. Poly(B) exhibited good thermal stability with decom-
position temperature at 399 °C. We next observed the glass
transition temperatures (Tg) of poly(B) (Mn = 30 000) using
differential scanning calorimetry (DSC). The Tg value of
poly(B) was estimated as high as 216 °C, as shown in Figure 6.
This temperature is almost 110 °C higher than the Tg value of
polystyrene (∼100 °C). The large improvement in Tg for
poly(B) may result from the incorporation of the bulky triphe-
nylamine moiety with tert-butyl group, causing the reduction in
chain mobility. Therefore, this relatively high Tg value can be
a thermal advantage for material used in organic electronic
devices.
Photophysical Properties. The absorption and emission
spectra of B and poly(B) (Mn = 30 000) are shown in Figure 7,
and their photophysical properties are summarized in
Table 4. For poly(B) in toluene solution, the maximum
absorption peak was observed at 332 nm, which is slightly
blue-shifted compared to its monomer B, presumably due to
reduction in π-conjugation caused by the twisted conforma-
tion of vinyl backbone.42 This absorption spectrum is as-
cribed to the π-π* transition of the triphenylamine moiety.
The absorption spectrum of poly(B) in the solid state was
almost identical to that in toluene solution.
References and Notes
(1) Shirota, Y.; Kageyama, H. Chem. Rev. 2007, 107, 953–1010.
(2) Walzer, K.; Maennig, B.; Pfeiffer, M.; Leo, K. Chem. Rev. 2007,
107, 1233–1271.
(3) Thelakkat, M. Macromol. Mater. Eng. 2002, 287, 442–461.
(4) Deng, L.; Furuta, P. T.; Garon, S.; Li, J.; Kavulak, D.; Thompson,
ꢀ
M. E.; Frechet, J. M. J. Chem. Mater. 2006, 18, 386–395.
(5) Yeh, K. M.; Lee, C. C.; Chen, Y. Synth. Met. 2008, 158, 565–571.
(6) Li, Y.; Xue, L.; Xia, H.; Xu, B.; Wen, S.; Tian, W. J. Polym. Sci.,
Part A: Polym. Chem. 2008, 46, 3970–3984.
(7) Liou, G. S.; Lin, H. Y.; Hsieh, Y. L.; Yang, Y. L. J. Polym. Sci.,
Part A: Polym. Chem. 2007, 45, 4921–4932.
(8) Lee, S. K.; Ahn, T.; Cho, N. S.; Lee, J. I.; Jung, Y. K.; Lee, J.; Shim,
H. K. J. Polym. Sci., Part A: Polym. Chem. 2007, 45, 1199–1209.
(9) Mutaguchi, D.; Okumoto, K.; Ohsedo, Y.; Moriwaki, K.; Shirota,
Y. Org. Electron. 2003, 4, 49–59.
(10) Park, M. H.; Huh, J. O.; Do, Y.; Lee, M. H. J. Polym. Sci., Part A:
Polym. Chem. 2008, 46, 5816–5825.
(11) Park, J. H.; Yun, C.; Park, M. H.; Do, Y.; Yoo, S.; Lee, M. H.
Macromolecules 2009, 42, 6840–6843.
(12) Jiang, X. Z.; Liu, S.; Liu, M. S.; Herguth, P.; Jen, A. K. Y.; Fong,
H.; Sarikaya, M. Adv. Funct. Mater. 2002, 12, 745–751.
(13) Liu, S.; Jiang, X.; Ma, H.; Liu, M. S.; Jen, A. K. Y. Macromolecules
2000, 33, 3514–3517.
(14) Se, K.; Kijima, M.; Fujimoto, T. Polym. J. 1988, 20, 791–799.
(15) Bellmann, E.; Shaheen, S. E.; Grubbs, R. H.; Marder, S. R.;
Kippelen, B.; Peyghambarian, N. Chem. Mater. 1999, 11, 399–407.
(16) Feast, W. J.; Peace, R. J.; Sage, I. C.; Wood, E. L. Polym. Bull.
1999, 42, 167–174.
(17) Tew, G. N.; Pralle, M. U.; Stupp, S. I. Angew. Chem., Int. Ed. 2000,
39, 517–521.
(18) Natori, I.; Natori, S.; Usui, H.; Sato, H. Macromolecules 2008, 41,
3852–3858.
(19) Higashihara, T.; Ueda, M. Macromolecules 2009, 42, 8794–8800.
(20) Behl, M.; Hattemer, E.; Brehmer, M.; Zentel, R. Macromol. Chem.
Phys. 2002, 203, 503–510.
(21) Lindner, S. M.; Thelakkat, M. Macromolecules 2004, 37, 8832–8835.
(22) Tsutsumi, N.; Murano, T.; Sakai, W. Macromolecules 2005, 38,
7521–7253.
In the solid state, the maximum emission peak of poly(B) was
observed at 412 nm, as shown in Figure 7b. This emission
spectrum was red-shifted by 17 nm from the corresponding
solution spectrum. Such a phenomenon probably occurred due
to intermolecular interactions between polymer chains leading
to better conjugation in solid state than in solution. More studies
on the luminescence properties will be undertaken in the near
future.
(23) Lindner, S. M.; Thelakkat, M. Macromol. Chem. Phys. 2006, 207,
2084–2092.
(24) Deng, L.; Furuta, P. T.; Garon, S.; Li, J.; Kavulak, D.; Thompson,
Conclusions
ꢀ
M. E.; Frechet, J. M. J. Chem. Mater. 2006, 18, 386–395.
The anionic polymerization of the styrene derivatives contain-
ing triphenylamine moieties, 4,40-vinylphenyltriphenylamine (A)
and 4,40-vinylphenyl-N,N-bis(4-tert-butylphenyl)benzenamine
(B), was carried out with various initiators in THF at -78 °C, but
an intermolecular side reaction took place between the polymer
chains during the course of the polymerization of A. In contrast,
the anionic polymerization of B, in which the site where propa-
gating chain-end carbanion attacks was protected by the intro-
duction of a tert-butyl group, was carried successfully out with
sec-BuLi and K-Naph as initiators in THF at-78 °C without any
intermolecular side reaction. These results indicate strongly that
(25) Peter, K.; Thelakkat, M. Macromolecules 2003, 36, 1779–1785.
(26) Bacher, E.; Bayerl, M.; Rudati, P.; Reckefuss, N.; Muller, C. D.;
€
Meerholz, K.; Nuyken, O. Macromolecules 2005, 38, 1640–1647.
(27) Hreha, R. D.; Haldi, A.; Domercq, B.; Barlow, S.; Kippelen, B.;
Marder, S. R. Tetrahedron 2004, 60, 7169–7176.
(28) Bellmann, E.; Shaheen, S. E.; Thayumanavan, S.; Barlow, S.;
Grubbs, R. H.; Marder, S. R.; Kippelen, B.; Peyghambarian, N.
Chem. Mater. 1998, 10, 1668–1676.
(29) Kimyonok, A.; Domercq, B.; Haldi, A.; Cho, J. Y.; Carlise, J. R.;
Wang, X. Y.; Hayden, L. E.; Jones, S. C.; Barlow, S.; Marder, S. R.;
Kippelen, B.; Weck, M. Chem. Mater. 2007, 19, 5602–5608.
(30) Nakahama, S.; Hirao, A. Prog. Polym. Sci. 1990, 15, 299–335.

8408 Macromolecules, Vol. 43, No. 20, 2010
Kang et al.
(31) Hirao, A.; Nakahama, S. Prog. Polym. Sci. 1992, 17, 283–317.
(32) Hirao, A.; Loykulnant, S.; Ishizone, T. Prog. Polym. Sci. 2002, 27,
1399–1471.
(33) Hirao, A.; Hayashi, M.; Loykulnant, S.; Sugiyama, K.; Ryu, S. W.;
Haraguchi, N.; Matsuo, A.; Higashihara, T. Prog. Polym. Sci.
2005, 30, 111–182.
4132–4133. (i) Kang, N. G.; Changez, M.; Lee, J. S. Macromolecules
2007, 40, 8553–8559.
(37) (a) Cho, Y. S.; Lee, J. S. Macromol. Rapid Commun. 2001, 22, 638–
642. (b) Cho, Y. S.; Ihn, C. S.; Lee, H. K.; Lee, J. S. Macromol. Rapid
Commun. 2001, 22, 1249–1253. (c) Cho, Y. S.; Ihn, C. S.; Kim, S. W.;
Lee, J. S. Polymer 2001, 42, 7611–7616. (d) Cho, Y. S.; Lee, H. K.; Lee,
J. S. Macromol. Chem. Phys. 2002, 203, 2495–2500. (e) Cho, Y. S.;
Lee, J. S.; Cho, G. Polymer 2002, 43, 1197–1202.
(34) Hirao, A.; Tsunoda, Y.; Matsuo, A.; Sugiyama, K.; Watanabe, T.
Macromol. Res. 2006, 14, 272–286.
(35) Higashihara, T.; Inoue, K.; Nagura, M.; Hirao, A. Macromol. Res.
2006, 14, 287–299.
(38) (a) Thelakkat, M.; Schmidt, H.-W. Adv. Mater. 1998, 10, 219–223.
(b) Katsuma, K.; Shirota, Y. Adv. Mater. 1998, 10, 223–226.
(39) (a) McMurry, J. Organic Chemistry, 5th ed.; Thomson Learning:
New York, 1999; pp 605-616. (b) Streitwieser, A.; Heathcock, C. H.;
Kosower, E. M. Introduction to Organic Chemistry, 4th ed.; Macmillan:
New York, 1992; pp 702-705.
(36) (a) Lee, J. S.; Ryu, S. W. Macromolecules 1999, 32, 2085–2087.
(b) Shin, Y. D.; Kim, S. Y.; Ahn, J. H.; Lee, J. S. Macromolecules 2001,
34, 2408–2410. (c) Shin, Y. D.; Ahn, J. H.; Lee, J. S. Macromol. Rapid
Commun. 2001, 22, 1041–1045. (d) Shin, Y. D.; Ahn, J. H.; Lee, J. S.
Polymer 2001, 42, 7979–7985. (e) Ahn, J. H.; Lee, J. S. Macromol.
Rapid Commun. 2003, 24, 571–575. (f) Ahn, J. H.; Shin, Y. D.; Kim,
S. Y.; Lee, J. S. Polymer 2003, 44, 3847–3854. (g) Shin, Y. D.; Han,
S. H.; Samal, S.; Lee, J. S. J. Polym. Sci., Part A: Polym. Chem. 2005,
43, 607–615. (h) Ahn, J. H.; Shin, Y. D.; Nath, Y. G.; Park, S. Y.;
Rahman, M. S.; Samal, S.; Lee, J. S. J. Am. Chem. Soc. 2005, 127,
(40) Ishizone, T.;Sugiyama, K.;Hirao,A.;Nakahama, S.Macromolecules
1993, 26, 3009–3018.
(41) Ishizone, T.; Uehara, G.; Hirao, A.; Nakahama, S.; Tsuda, K.
Macromolecules 1998, 31, 3764–3774.
(42) Sugiyama, K.; Hirao, A.; Hsu, J. C.; Tung, Y. C.; Chen, W. C.
Macromolecules 2009, 42, 4053–4062.