Synthesis and characterization of new poly(silole-fluorene) copolymers

Article abstract of DOI:10.1166/jnn.2015.9289

New poly(silole-fluorene) copolymers were designed and synthesized. Copolymers were obtained by Suzuki coupling reaction with different ratio of fluorene and silole. The obtained copolymers were characterized by the spectroscopic methods such as FT-IR and

Full text of DOI:10.1166/jnn.2015.9289

Article
Journal of
Nanoscience and Nanotechnology
Vol. 15, 1742–1747, 2015
Copyright © 2015 American Scientific Publishers
All rights reserved
Printed in the United States of America
www.aspbs.com/jnn
Synthesis and Characterization of New
Poly(silole-fluorene) Copolymers
1
1
1
1
2ꢀ∗
Yun-Ji Lee , Jeong Cheol Park , Hui-Jun Yun , Jong-Man Park , and Yun-Hi Kim
1
School of Materials Science and Engineering and ERI, Gyeongsang National University, Jinju, 660-701, Korea
2
Department of Chemistry, Gyeongsang National University, Jinju, 660-701, Korea
New poly(silole-fluorene) copolymers were designed and synthesized. Copolymers were obtained
by Suzuki coupling reaction with different ratio of fluorene and silole. The obtained copolymers
1
were characterized by the spectroscopic methods such as FT-IR and H-NMR spectroscopies. The
resulting copolymers were soluble in common organic solvents such as toluene, tetrahydrofurane,
chloroform, chlorobenzene, etc. The obtained copolymers showed thermal stabilities, which were
characterized by TGA and DSC. PLEDs with device configurations of ITO/PEDOT:PSS/Copolymer
2
I∼VI/LiF/Al. The best device performances, with maximum brightness of 231.5 cd/m at a current
2
density (J) of 408.3 mA/cm , and a maximum luminance efficiency of 0.115 cd/A, were achieved in
the composition of fluorene and silole moiety (0.9:0.1).
Keywords: Polyfluorene, Silole Moiety, OLED, PLED.
Delivered by Ingenta to: Nanyang Technological University
IP: 5.62.152.201 On: Thu, 16 Jun 2016 21:15:11
Copyright: American Scientific Publishers
1
. INTRODUCTION
2. EXPERIMENTAL DETAILS
2.1. Material Preparation
All reagents and catalysts were purchased from Aldrich
and UMICORE. Other solvents were purchased from duk-
san and were further purified prior to use. All reagents pur-
chased comercially were used without further purification.
1
Organic light-emitting diodes (OLEDs) have attracted
attention due to their possible applications in flat panel
displays.2 Polymer light-emitting diodes (PLEDs) also
have attracted considerable interest due to their applica-
3
4
tions in large-area flat panel displays with high-efficiency.
For the highly efficient PLED devices, charge injection and
transport from both the anode and cathode should be bal-
anced at the emitting layer to yield high maximum exciton
2
.2. Synthesis
2.2.1. Synthesis of Bisꢃphenylacetylꢄdiphenylsilane ꢃ1ꢄ
5
6ꢀ7
formation. Polyfluorene derivatives are well known for
n-Butyllithium (2.5 M in hexane, 70.8 mL, 0.761 mol)
was slowly added to phenyl acetylene (13.9 g, 0.136 mol)
8
blue light emission.
It is reported that the silole moiteies are able to
transport electrons efficiently. Silole-containg molecules
ꢀ
in anhydrous tetrahydrofuran (THF) (200 mL) at − 78 C.
After 1 h stirring at room temperature, diphenyl dichlorosi-
lane (15 g, 0.059 mol) was slowly dropped into the mixture
∗
∗
have low LUMO energy level by a ꢁ → ꢂ conju-
9
gation and increase their electron affinities and have
been used as electron-transporting with the high electron
mobility.
ꢀ
at − 78 C and stirred at room temperature. After 12 h, the
1
0
reaction was terminated by the addition of ice water and
extracted with ethyl acetate (EA). The crude product was
purified by column chromatography and re-crystallization
with hexane/EA: 20/1 as eluent. Yield: 13 g (57%). m·p:
In this study, we designed the copolymer with fluo-
rene as blue emitting moiety and silole as possessing
high electron transport ability. We studied the physical,
optical, electrochemical properties and performance of
PLED according to the composition of fluorene and silole
moiety.
ꢀ
−1
174 C. FT-IR (KBr) (cm ): 3069–3000 (aromatic C–H),
1
487, 1441, 1426 (aromatic C C), 2148 (C C), 1112
1
(
(
7
Si–C); H NMR (300 MHz , CDCl , ppm) ꢅ = 7ꢆ89∼7ꢆ92
3
dd, 4 H), 7.60∼7.74 (dd, 4 H), 7.35∼7.51 (m, 6 H),
.09∼7.28 (m, 6 H). Anal. Calcd. for C H Si: C, 87.45;
2
8
20
∗
Author to whom correspondence should be addressed.
H, 5.24. Found: C, 86.85; H, 5.30.
1
742
J. Nanosci. Nanotechnol. 2015, Vol. 15, No. 2
1533-4880/2015/15/1742/006
doi:10.1166/jnn.2015.9289

Lee et al.
Synthesis and Characterization of New Poly(silole-fluorene) Copolymers
2
.2.2. Synthesis of 2,5-diꢃbromopyridylꢄ-1,1-diph-enyl-
,4-diphenylsilole ꢃ2ꢄ
Lithium (0.032 g, 0.004 mol) and naphthalene (4.2 g,
.032 mol) in THF (50 mL) were stirred for 6 h.
2.2.3. Synthesis of
2,7-bisꢃethyleneboronateꢄ-9,9 -dihexylfluorene ꢃ3ꢄ
Synthesis was referenced by literature method. Yield:
ꢁ
3
1
1
ꢀ
−1
0
14 g (95%). m·p: 120 C. FT-IR (KBr) (cm ): 3053, 3033
Bis(phenylacetyl)diphenylsilane (3 g, 0.007 mol) in THF
(aromatic C–H), 2964–2842 (aliphatic C–H), 1488, 1472,
ꢀ
1
was dropped to the mixture at − 78 C. After 1 h stir-
1453 (aromatic C C); H NMR (300 MHz , CDCl , ppm)
3
ring at room temperature, 1 M ZnCl was slowly added
ꢅ = 7ꢆ68∼7ꢆ84 (m, 6 H), 4.43 (s, 8 H), 1ꢆ99∼2ꢆ06 (m,
4 H), 1ꢆ01∼1ꢆ27 (m, 12 H), 0ꢆ73∼0ꢆ79 (t, 6 H), 0.58 (br
s, 4 H). Anal. Calcd. for C H B O ; C, 73.44; H, 8.50;
2
ꢀ
to the mixture at 0 C and stirred for further an hour.
2
,6-dibromopyridine (3.8 g, 0.016 mol) and PdCl (PPh )
2 3 2
29 40
2
4
was added and the result solution was refluxed for 16 h
O, 13.44. Found: C, 73.40; H, 8.49; O, 13.55.
ꢀ
at 85∼90 C. Once the reaction was completed, the crude
ꢁ
product was worked up with water. The product was
extracted with EA. The crude product was purified by
column chromatography with hexane/EA: 20/1 as eluent
and re-crystallization with methylene chloride (MC) and
2.2.4. Synthesis of Polyꢃ2,7-ꢃ9,9 -dihexyl fluoreneꢄ -co-
9
9
2,5-ꢃdipyridyl-1,1-diphenyl-3,4-diphenylsilole1ꢄ
ꢃCopolymer Iꢄ ꢃ4ꢄ
2,5-Di(bromopyridyl)-1,1-diphenyl-3,4 diphenyl silole
ꢀ
ꢁ
hexane. Yield: 2 g (36%). m · p: 244∼255 C. FT-IR
(0.01 g, 0.014 mmol), 2,7-dibromo-9,9 -dihexyl fluorene
−
1
ꢁ
(
KBr) (cm ): 3046 (aromatic C–H), 1465, 1427 (aro-
(0.345 g, 0.701 mmol) and 2,7-bis(ethyleneboronate)-9,9 -
matic C C), 1566 (C N), 1116 (Si–C), 1023 (C–Br);
dihexylfluorene (0.33 g, 0.611 mmol) were dissolved in
THF (30 mL) and 2 M K CO (50 mL). After degassing,
1
7
6
H NMR (300 MHz, CDCl , ppm) ꢅ = 7ꢆ9 (d, 4 H),
3
2
3
.3∼7.45 (m, 6 H), 7.12∼7.2 (t, 6 H), 7.09∼6.9 (m, 8 H),
.35∼6.45 (m, 2 H). Anal. Calcd. for C H Br N Si:
Pd(PPh3)4 was added to the mixture and stirred for
ꢀ
72 h at 80 C. Subsequently, phenylboronic acid and
3
8
26
2
2
C, 65.34; H, 3.75; N, 4.01. Found: C, 55.14; H, 3.85,
N, 4.26.
bromobenzene were injected into the reaction mixture
and the reaction was stirred for 6 h. After precipitation
Delivered by Ingenta to: Nanyang Technological University
n-BuLi
H
+
Si
Si
IP: 5.62.152
C
.
l
201 On: Thu, 16 Jun 2016 21:15:11
C
l
THF
Copyright: American Scientific Publishers
(
1)
Br
Br
Br
N
N
LiNaph
THF
Si
ZnCl2
THF
Si
N
PdCl2(PPh3)2
Si
Li
Li
ClZn
ZnCl
+
Br
THF
(2)
ethylene glycol
toluene
O
O
(HO)2B
B(OH)2
B
B
O
O
(3)
Br
Br
N
N
Si
O
O
Br
Br
B
B
+
+
O
O
(3)
N
Si
N
Pd(PPh3)4
M K2CO3, THF
n
m
2
n = 0.01 m = 0.99 (Copolymer I)
0.05
0.10
0.20
0.30
0.50
0.95 (Copolymer II)
0.90 (Copolymer III)
0.80 (Copolymer IV)
0.70 (Copolymer V)
0.50 (Copolymer VI)
Figure 1. Synthetic routes of copolymer.
J. Nanosci. Nanotechnol. 15, 1742–1747, 2015
1743

Synthesis and Characterization of New Poly(silole-fluorene) Copolymers
Lee et al.
ꢁ
from methanol, the desired polymer was obtained. Yield: 2.2.9. Synthesis of Polyꢃ2,7-ꢃ9,9 -dihexylfluoreneꢄ -co-
5
0
−1
0
.58 g (50%). FT-IR (KBr) (cm ): 3059 (aromatic C–H),
2,5-ꢃdipyridyl-1,1-diphenyl-3,4-diphenyl-siloleꢄ ꢄ
50
2
907–2854 (aliphatic C–H), 1440 (aromatic C C), 1567
ꢃCopolymer VIꢄ ꢃ9ꢄ
Copolymer VI was synthesized with the same method used
1
(C
N), 1115 (Si–C); H NMR (300 MHz, CDCl , ppm)
3
−1
ꢅ = 7ꢆ87∼7ꢆ81 (m, 9 H), 7ꢆ4∼7ꢆ7 (m, 18 H), 6ꢆ6∼7ꢆ2 (m,
for Copolymer I. Yield: 0.2 g (27%), FT-IR (KBr) (cm ):
3059 (aromatic C–H), 2907–2854 (aliphatic C–H), 1440
(aromatic C C), 1567 (C N), 1115 (Si–C). Anal. Calcd.
for (C H N Si) : C, 86.65; H, 6.93; N, 3.21. Found: C,
5
1
2
1
1
H), 2.1 (br s, 4 H), 1ꢆ16∼1ꢆ58 (s, 12 H), 0ꢆ79∼0ꢆ81 (d,
0 H), 13C NMR (300 MHz, CDCl , ppm) ꢅ = 13ꢆ9, 22.5,
3
3.6, 23.7, 29.1, 29.7, 29.8, 31.4, 31.7, 40.1, 40.4, 55.3,
21.1, 121.4, 126.2, 127.2, 127.5, 128.4, 128.7, 130.1,
34.3, 139.0, 152.5. Anal. Calcd. for (C H N Si) :
6
3
60
2
n
8
5.55: H, 6.81, N, 3.12.
6
3
60
2
n
C, 86.65; H, 6.93; N, 3.21. Found: C, 85.55; H, 6.81,
N, 3.12.
ꢁ
2
.2.5. Synthesis of Poly(2,7-ꢃ9,9 -dihexylfluoreneꢄ -co-
9
5
2
,5-ꢃdipyridyl-1,1-diphenyl-3,4-diphenylsiloleꢄ5ꢄ
ꢃCopolymer IIꢄ ꢃ5ꢄ
Copolymer II was synthesized with the same method
used for Copolymer I. Yield: 0.42 g (35%), FT-
−1
IR (KBr) (cm ꢄ: 3059 (aromatic C–H), 2907–2854
aliphatic C–H), 1440 (aromatic C C), 1567 (C N),
115 (Si–C). Anal. Calcd. for (C H N Si) : C, 86.65;
(
1
6
3
60
2
n
H, 6.93; N, 3.21. Found: C, 85.55; H, 6.81, N,
3
.12.
.2.6. Synthesis of Polyꢃ2,7-ꢃ9,9 -dihexylfluoreneꢄ -co-
ꢁ
2
9
0
2
,5-ꢃdipyridyl-1,1-diphenyl-3,4-diphenylsiloleꢄ ꢄ
10
Delivered by Ingenta to: Nanyang Technological University
IP: 5.62.152.201 On: Thu, 16 Jun 2016 21:15:11
ꢃCopolymer IIIꢄ ꢃ6ꢄ
Copolymer III was synthesized with the same method
Copyright: American Scientific Publishers
used for Copolymer I. Yield: 0.32 g (29%), FT-IR (KBr)
cm ): 3059 (aromatic C–H), 2907–2854 (aliphatic C–H),
440 (aromatic C C), 1567 (C N), 1115 (Si–C). Anal.
Calcd. for (C H N Si) : C, 86.65; H, 6.93; N, 3.21.
−
1
(
1
6
3
60
2
n
Found: C, 85.55; H, 6.81, N, 3.12.
ꢁ
2
.2.7. Synthesis of Polyꢃ2,7-ꢃ9,9 -dihexylfluoreneꢄ -co-
8
0
2
,5-ꢃdipyridyl-1,1-diphenyl-3,4-diphenylsiloleꢄ ꢄ
20
ꢃCopolymer IVꢄ ꢃ7ꢄ
Copolymer IV was synthesized with the same method
used for Copolymer I. Yield: 0.25 g (20%), FT-IR (KBr)
−
1
(
cm ): 3059 (aromatic C–H), 2907–2854 (aliphatic C–H),
440 (aromatic C C), 1567 (C N), 1115 (Si–C). Anal.
Calcd. for (C H N Si) : C, 86.65; H, 6.93; N, 3.21.
1
6
3
60
2
n
Found: C, 85.55; H, 6.81, N, 3.12.
ꢁ
2
.2.8. Synthesis of Polyꢃ2,7-ꢃ9,9 -dihexylfluoreneꢄ -co-
7
0
2
,5-ꢃdipyridyl-1,1-diphenyl-3,4-diphenylsiloleꢄ ꢄ
30
ꢃCopolymer Vꢄ ꢃ8ꢄ
Copolymer V was synthesized with the same method
used for Copolymer I. Yield: 0.32 g (37%), FT-
−1
IR (KBr) (cm ): 3059 (aromatic C–H), 2907–2854
aliphatic C–H), 1440 (aromatic C C), 1567 (C N),
115 (Si–C). Anal. Calcd. for (C H N Si) : C, 86.65;
(
1
6
3
60
2
n
H, 6.93; N, 3.21. Found: C, 85.55; H, 6.81, N,
.12.
Figure 2. 1H-NMR of copolymer (a) copolymer I, (b) copolymer II,
(c) copolymer III, (d) copolymer IV, (e) copolymer V, (f) copolymer VI.
3
1
744
J. Nanosci. Nanotechnol. 15, 1742–1747, 2015

Lee et al.
Synthesis and Characterization of New Poly(silole-fluorene) Copolymers
Table I. The thermal, optical and electrochemical properties of the copolymer.
UV (nm)
PL (nm)
Solution
ꢀ
ꢀ
el
M
Mw
PDI T ( C) T5% ( C) Solution Film
Film
HOMO (eV) LUMO (eV) Eg (eV)
g
Copolymer I
Copolymer II
Copolymer III 8,510 12,650 1.48
Copolymer IV 9,560 14,310 1.49
Copolymer V 11,180 17,660 1.57
10,980 19,900 1.81
8,090 13,120 1.62
88
87
104
115
134
142
280
289
294
312
314
320
384
379
377
373
363
353
380
378
373
369
363
424, 443
448
424, 445
421, 442
419, 444
449, 476
483
484
486
485
−5ꢆ61
−5ꢆ63
−5ꢆ61
−5ꢆ62
−5ꢆ63
−5ꢆ64
−3ꢆ16
−3ꢆ21
−3ꢆ39
−3ꢆ44
−3ꢆ46
−3ꢆ49
2.45
2.42
2.22
2.18
2.17
2.15
Copolymer VI 5,690
8,250 1.45
351 417, 447, 474
488
3
. RESULTS AND DISCUSSION
stability was increased. From the DSC data of the copoly-
3
.1. Synthesis and Characterization of the Copolymer
mers the glass transition temperature (T
g
) was observed
ꢀ
at 88∼134 C. The glass transition temperature was grad-
ually increased as the increasing ratio of silole moiety.
The introduction of rigid silole moiety can lead good to
increase thermal stability. Therefore the drawback of low
The synthesis of Copolymer I∼VI were prepared as
depicted in Figure 1. Copolymer I∼VI were obtained
by Suzuki coupling reaction with different ratio of flu-
orene and silole moiety (0.99: 0.01, 0.95: 0.05, 0.90:
Tg of dialkyl fluorene can be overcome (Fig. 3).
0
.10, 0.80: 0.20, 0.70: 0.30, 0.50: 0.50). The obtained
copolymers were purified by precipitation using methanol.
1
The structure of copolymer was studied by H-NMR.
3.3. Optical and Electrochemical Properties Analysis
1
The copolymer composition was comfirmed by H-NMR
The UV-visible absorption and photoluminescence spec-
−5
integration. As the decreasing ratio of fluorene, the
integration of alkyl protons was decreased (Fig. 2).
The copolymers showed good solubility in common
organic solvents, such as methylene chloride, tetrahydro-
furan, chloro-form, toluene and chlorobenzene. Gel per-
tra of the polymer both in chloroform (1 × 10 M) and
film state are shown in Figure 4. The UV-visible absorp-
tion was blue shift as increasing of mole ratio of silole
moiety from 384 to 363 nm for solution and 380 to
362 nm for film, respectively. It can be explained by the
meation chromatography (GPC) analysis determined the
introduction of kinked structure of meta pyridine-silole as
Delivered by Ingenta to: Nanyang Technological University
weight average molecular weig hI Pt :( 5M .6 2) .1t 5o 2 .b2e 0 1a rOo un n: dT hu, w1 e6 llJ ua sn i 2n 0h i1b 6i t e2 d1 :i 1n 5t e: r1 m1 olecular interaction. In general, it
W
Copyright: American Scientific Publishers
8
1
,200∼19,900 with a polydisoersity index (PDI) of around
is reported that poly-fluorene have low color purity due
to the excimer formaion in the long wavelength range.
In the new developed copolymers, the excimer emission
doesn’t represent because the ramdomly introduced meta-
.45∼1.81, against polystyrene standards. The molecular
weights and polydis persity indexes of the copolymers
were summarized in Table I.
1
2
kinked silole moiety is able to prevent the intermolecular
interaction.
3
.2. Thermal Analysis
The thermal properties of the polymers were evaluated
by thermal gravimetric analysis (TGA) and differential
scanning calorimetry (DSC). The 5% weight loss of the
copolymers was observed around from 280 C to 314 C.
As the increasing ratio of the silole moiety, the thermal
The electrochemical behaviors of these polymers were
investigated by cyclic voltammetry (CV). Their HOMO,
LUMO and band gap were summarized in Table I. HOMO
energy level of the copolymers were −5ꢆ61∼−5ꢆ64 eV
and LUMO energy level were −3ꢆ16∼−3ꢆ49 eV.
ꢀ
ꢀ
(
a)
(b)
Figure 3. The thermal properties of copolymer (a) TGA and (b) DSC curve.
J. Nanosci. Nanotechnol. 15, 1742–1747, 2015
1745

Synthesis and Characterization of New Poly(silole-fluorene) Copolymers
Lee et al.
Figure 4. The optical properties of copolymer (a) UV-visible spectra copolymer in solution, (b) UV-visible spectra in film, (c) PL spectra in solution
Delivered by Ingenta to: Nanyang Technological University
and (d) PL spectra in film.
IP: 5.62.152.201 On: Thu, 16 Jun 2016 21:15:11
Copyright: American Scientific Publishers
The copolymer shows the decreased LUMO energy level
as increasing silole ratio because of electron-withdrawing
property of silole moiety.
silole moiety or partial excimer format of fluorene moiety
in the aggregation state.
1
3
4
. CONCLUSION
3
.4. Device Performance
Devices with the configuration of indium tin oxide
ITO)/PEDOT:PSS/Copolymer/LiF/Al were fabricated.
The new blue copolymers with different composition of
silole and dihexyl fluorene were synthesized by Suzuki-
coupling reaction. As the increased composition of silole
moiety, the Tg of copolymers was increased. More-
over, the ꢇmax of UV-vis was blue-shifted, and LUMO
level was decreased due to introduction of non-copolanar
silole electron transporting property. The maximum current
efficiency of 0.115 cd/A and maximum brightness of
(
The CIE chromaticity coordinates and device perfor-
mance are summarized in Table II. The maximum lumi-
nance efficiency of 0.115 cd/A and maximum brightness
2
of 231.5 cd/m with CIE (0ꢆ24ꢀ0ꢆ38) was observed for
copolymer II. Luminance efficiencies of copolymers are
extremely low. That is attributed to imperfect intra- and
intermolecular energy transfer from fluorene moiety to
2
231.5 cd/m with CIE (0ꢆ24ꢀ0ꢆ38) was observed at
copolymer II.
Acknowledgment: This work was supported by the
Industrial Strategic Technology Development Program
Table II. Device performance characteristics of the ITO/
PEDOT:PSS/Copolymer/LiF/Al device in air at room temperature.
[10045269, Development of Soluble TFT and Pixel For-
Luminance
efficiency
(cd/A)
mation Materials/Process Technologies for AMOLED TV]
funded by MOTIE/KEIT.
J
Brightness
(cd/m )
(mA/cm2)
2
CIE (xꢀy)
Von
Copolymer I
Copolymer II
Copolymer IV 11
Copolymer V
Copolymer VI
Copolymer VII
6
8
0ꢆ053
0ꢆ115
0ꢆ011
0ꢆ066
0ꢆ0005
0ꢆ0006
280.4
408.3
523.9
206.2
249.0
355.4
80
231ꢆ5
41
22
0ꢆ23
2ꢆ21
(0ꢆ16ꢀ0ꢆ11)
(0ꢆ24ꢀ0ꢆ38)
(0ꢆ26ꢀ0ꢆ38)
(0ꢆ38ꢀ0ꢆ48)
(0ꢆ26ꢀ0ꢆ51)
(0ꢆ34ꢀ0ꢆ41)
References and Notes
1
. S. O. Kim, K. Thangaraju, S. O. Jung, W. Lu, S. M. Park, J. H.
Lee, J. I. Lee, H. Y. Chu, Y. H. Kim, and S. K. Kwon, J. Nanosci.
Nanotechnol. 12, 4375 (2012).
11
4
3
2. H. T. Park, J. H. Lee, I. Kang, H. Y. Chu, J. I. Lee, S. K. Kwon,
and Y. H. Kim, J. Mater. Chem. 22, 2695 (2012).
1
746
J. Nanosci. Nanotechnol. 15, 1742–1747, 2015

Lee et al.
Synthesis and Characterization of New Poly(silole-fluorene) Copolymers
3
4
5
6
. R. Kim, S. H. Lee, K. H. Kim, Y. J. Lee, S. K. Kwon, J. J. Kim,
and Y. H. Kim, Chemcomm. 49, 4664 (2013).
. Y. S. Park, J. W. Kang, D. M. Kang, J. W. Park, Y. H. Kim, S. K.
Kwon, and J. J. Kim, Advanced Mater. 20, 1957 (2008).
. Y. H. Kim, D. C. Shin, and S. K. Kwon, Advanced. Mater. 13, 1690
8. D. H. Oh, Q. Zhao, S. O. Kim, H. T. Park, Y. H. Kim, Y. S. Park, J. J.
Kim, and S. K. Kwon, Macromolecular Research 19, 629 (2011).
9. H. T. Park, D. C. Shin, S. C. Shin, J. H. Kim, S. K. Kwon, and Y. H.
Kim, Macromolecular Research 19, 965 (2011).
10. R. Kim, D. H. Oh, M. C. Hwang, J. Y. Baek, S. C. Shin, S. K.
Kwon, and Y. H. Kim, J. Nanosci. Nanotechnol. 12, 4370 (2012).
11. J. W. Kim, S. J. Park, Y. H. Kim, D. C. Shin, H. You, and S. K.
Kwon, Polymer 50, 102 (2009).
12. R. Kim, D. H. Oh, M. C. Hwang, J. Y. Baek, S. C. Shin, S. K.
Kwon, and Y. H. Kim, J. Nanosci. Nanotechnol. 12, 1533 (2012).
13. F. Wang, J. Luo, K. Yang, J. Chen, F. Huang, and Y. Cao,
Macromolecules 38, 2253 (2005).
(
2001).
. S. H. Jang, T. B. Tai, J. H. Park, H. J. Jeong, E. J. Chun, Y. H. Kim,
S. G. Lee, O. M. J. Singh, Y. J. Yoon, and S. K. Kwon, Macro-
molecular Research 18, 185 (2010).
7. I. Kang, J. A. Hong, R. Kim, J. W. Jang, J. Y. Hwang, J. H. Kim,
S. K. Kwon, and Y. H. Kim, Macromolecular Research 21, 450
(
2013).
Received: 15 June 2013. Accepted: 23 September 2013.
Delivered by Ingenta to: Nanyang Technological University
IP: 5.62.152.201 On: Thu, 16 Jun 2016 21:15:11
Copyright: American Scientific Publishers
J. Nanosci. Nanotechnol. 15, 1742–1747, 2015
1747