Donor-acceptor copolymers containing the phthalazinone-thiophene structure synthesized by classical nucleophilic aromatic polymerization

Article abstract of DOI:10.1039/c5ra03771a

A series of new donor-acceptor copolymers based on a novel monomer containing phthalazinone and thiophene structures, were synthesized by classical nucleophilic displacement step polymerization reaction, and then were fully characterized. Their thermal, optical, electrochemical properties and quantum chemical calculations were investigated in detail. The comparisons between the linkage of ketone/di-ketone/sulfone groups and phenyl/naphthalene groups in the resulting polymer backbone were carried out to explore the relationship of the structure and the properties in the polymer system. The number average molecular weights of the resulting copolymers are 15 kDa-24 kDa. All of the copolymers are stable up to 441 °C, and their 5% weight loss temperatures are higher than 489°C. Their optical band gap and HOMO energy levels vary from 2.36 eV to 2.76 eV and -5.16 eV to -5.51 eV, respectively. The soluble copolymers obtained exhibit blue-fluorescence. Their photoluminescence quantum yield ranges from 0.04 to 0.28 in N-methyl-2-pyrrolidone. These non-ether bond polymers may be potential candidates in photoelectric application.

Full text of DOI:10.1039/c5ra03771a

RSC Advances
View Article Online
View Journal | View Issue
PAPER
Donor–acceptor copolymers containing the
phthalazinone–thiophene structure synthesized by
classical nucleophilic aromatic polymerization†
Cite this: RSC Adv., 2015, 5, 30445
a
a
a
b
Jianhua Han, Kuanyu Yuan, Cheng Liu, Jinyan Wang and Xigao Jianb
*
A series of new donor–acceptor copolymers based on a novel monomer containing phthalazinone and
thiophene structures, were synthesized by classical nucleophilic displacement step polymerization
reaction, and then were fully characterized. Their thermal, optical, electrochemical properties and
quantum chemical calculations were investigated in detail. The comparisons between the linkage of
ketone/di-ketone/sulfone groups and phenyl/naphthalene groups in the resulting polymer backbone
were carried out to explore the relationship of the structure and the properties in the polymer system.
The number average molecular weights of the resulting copolymers are 15 kDa–24 kDa. All of the
copolymers are stable up to 441 ꢀC, and their 5% weight loss temperatures are higher than 489 ꢀC. Their
optical band gap and HOMO energy levels vary from 2.36 eV to 2.76 eV and ꢁ5.16 eV to ꢁ5.51 eV,
respectively. The soluble copolymers obtained exhibit blue-fluorescence. Their photoluminescence
quantum yield ranges from 0.04 to 0.28 in N-methyl-2-pyrrolidone. These non-ether bond polymers
may be potential candidates in photoelectric application.
Received 3rd March 2015
Accepted 13th March 2015
DOI: 10.1039/c5ra03771a
www.rsc.org/advances
poly(phthalazinone ether ketone)s were rst successfully
synthesized in 1993 by classical nucleophilic aromatic substi-
tution reactions as shown in Scheme 1.4 The rigid asymmetric
Introduction
Conjugated polymers have attracted an increasing amount of
attention in recent decades for various organic electronic
devices such as organic light-emitting diodes (OLEDS), organic
eld-effect transistors (OFETs) and polymer solar cells (PSCs),
because of their potential advantages over inorganic and small-
molecule organic semiconductors.1 Polymeric materials usually
have better lm-forming ability, solution process ability, and
mechanical properties.2 Researchers have been devoting
themselves to develop cheap polymer materials having excellent
photoelectric property.
Our group has been focusing on exploring heat resistant
polymers based on the asymmetric monomer 1,2-dihydro-4-(4-
hydrox-yphenyl)-1-(2H)-phthalazinone (DHPZ) (Fig. 1). As
reported in our previous study, the NH group in DHPZ behaves
like a phenolic OH group with the result that DHPZ can react
with activated dihalo compounds to synthesize high molecular
weight polymers via combined C–N and C–O condensation
reactions.3 For example, poly(phthalazinone ether sulfone)s and
phenyl–phthalazinone structures in the polymer main chains
improve the solubility of the resulting polymers with main-
taining excellent thermostability, high glass transition temper-
ature and mechanical properties.5–11 These high performance
polymers have been widely used in industrial applications, such
as optical wave guides lms, ultraltration and nanoltration
membranes, and lithium-ion batteries functional lms, anion
exchange membrane materials used for vanadium redox ow
battery applications, dielectric energy storage thin lms, and
proton exchange membrane materials for fuel cells.12–17 On the
other side, DHPZ can be used as a acceptor due to the C]N
bond and lactam of the phthalazinone structure.18 Also its sp3
hybrid nitrogen atom in DHPZ has better planarity than
aPolymer Science & Materials, Chemical Engineering College, Dalian University of
Technology, Dalian, 116024, China
bState Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian,
116024, China. E-mail: wangjinyan@dlut.edu.cn
† Electronic supplementary information (ESI) available: 1H-NMR and 13C-NMR
spectrum of M2 and polymers, MALDI-TOF, IR, DSC, CV and HPLC-MS
spectrum of M2, DSC and CV curves of polymers, solubility table of monomers
and copolymers in organic solvent. See DOI: 10.1039/c5ra03771a
Fig. 1 Energy-minimized conformation of DHPZ determined using
DFT (calculated by Gaussian 09W at the B3LYP/6-31G**level).
This journal is © The Royal Society of Chemistry 2015
RSC Adv., 2015, 5, 30445–30455 | 30445

View Article Online
RSC Advances
Paper
Scheme 1 Synthetic route of poly(phthalazinone ether)s.
classical triphenylamine structure.19 The special structure of
DHPZ makes it attractive for constructing n-type and donor–
acceptor polymers. However, to our knowledge, few papers
report about the applications of phthalazinone-containing
polymers in optoelectronic materials. One of the main
reasons is that the existence of ether bond in the polymer main
chain interrupts conjugation effect. Thus, to eliminate the ether
bond and prolong the conjugated bond length in the
phthalazinone-containing polymers can broaden their applica-
tion into optoelectronic materials eld. The concept of our
design is summarized in Scheme 1.
In this paper, di-NH end-capped monomer M1 was designed
and then synthesized (Scheme 2). Monomer M1 possesses
several virtues: (1) its NH group can react with various dihalo-
compounds (–F, –Cl, –Br, –I) catalyzed by low costly base
through classical nucleophilic aromatic substitution polymeri-
zation. (2) By virtue of the C]N bond and lactam structure, its
polymers enrich the typical imide- and amide-functionalized
polymer semiconductor family, which has the high electron
deciency and the capability to self-assemble into ordered
structures.20 (3) Its derivative M2 from the reaction of M1 and
1-bromododecane greatly exhibits potential blue light emitting
with 54% of photoluminescence quantum yield (PLQY),
compared to bi(9,9-diaryluorene)s with PLQY ¼ 70% and
biuorene series compound with PLQY ¼ 60%.21 (4)Its polymers
also have excellent thermal and chemical stability. Thus herein
the di-NH group of M1 polymerized with di-halogenated
compounds by classical nucleophilic aromatic substitution
polymerization to produce a series of “non-ether bond” poly-
mers (Scheme 3). In order to comparison with traditional
poly(phthalazinone ether)s and commercial poly(aryl ether)s
synthesized by the same polymerization method,22 the common
monomers used in poly(aryl ether)s like M3 ꢂ M7 were chosen
in our work. Also, weak conjugated groups such as ketone/di-
Scheme 3 Synthetic route and structures of copolymers.
ketone/sulfone groups give polymers, without alkyl substitu-
ents, enough solubility in organic solvent for spin-coating
process. The thermal properties, optical properties, electro-
chemical properties, quantum chemical calculations (B3LYP/6-
31G**) by Gaussian 09 package23 and physical properties of the
resulting polymers were investigated in details. In addition, the
comparisons between the linkage of ketone/di-ketone/sulfone
groups and phenyl/naphthalene groups in the backbone of
the resulting polymers were carried out to explore the rela-
tionship of structure and property in our polymer system.
Experimental
Materials
Unless otherwise indicated, starting materials were obtained
from Aldrich or Alfa Aesar and were used without further
purication. Solvent and other common reagents were obtained
from Shanghai Energy Chemical. THF was distilled from
benzophenone and sodium under an inert N2 atmosphere prior
to use. Quinoline was puried by distillation under vacuum.
Commercial cuprous chloride was dissolved in concentrated
hydrogen chloride and the resulting solution was ltered
through an acid funnel to remove the insoluble substance. The
liquid obtained was then diluted by pure water then to collect
the white precipitate. The white solid was washed by methanol
and ether, respectively, and then kept in a desiccator. CuCl/
quinolone catalyst was prepared as the literature reported.3
Methods instrumentation
1H-NMR (400 Hz) and 13C-NMR (100 Hz) spectra were obtained
with a Brucker spectrometer at an operating temperature of
25 ꢀC using CDCl3 as solvents. HPLC-MS analyses were per-
formed on a HP1100LC/MSD instrument. Gel permeation
chromatography (GPC) analysis was carried out on a HP 1090
HPLC instrument equipped with 5 mm phenogel columns
˚
(linear, 4 ꢃ 500 A) arranged in series with chloroform as solvent
and a UV detector at 254 nm. And the values were calibrated
versus polystyrene standard. Matrix-assisted laser desorption
ionization time-of-ight mass spectroscopy (MALDI-TOF-MS)
analyses were performed on a Micromass GC-TOF CA 156
MALDI-TOF/MS. Infrared measurements were performed on a
Scheme 2 Synthesis of Di-NH capped monomers M1 and M2.
30446 | RSC Adv., 2015, 5, 30445–30455
This journal is © The Royal Society of Chemistry 2015

View Article Online
Paper
RSC Advances
Thermo Nicolet Nexus 470 Fourier transform infrared (FT-IR) hexamethylphosphoric triamide (HMPA) (6 mL) and toluene (10
spectrometer. UV-visible absorption was measured with a Per- mL). The mixture was heated to 145 ꢀC (oil bath) under an argon
kinElmer Lambda 35 UV-vis spectrometer. Fluorescence spectra atmosphere and maintained at this temperature for 4 h to
were obtained using a Hitachi F-4500 spectrouorometer with a remove water produced during the reaction. Aer complete
xenon lamp and 1.0 cm quartz cells. Elemental analysis was dehydration, the reaction temperature was increased to 190–195
measured on a Vario ELIII CHNOS Elementaranalysator from ꢀC (oil bath) and the toluene was distilled. The yellow slurry in
ꢀ
Elementaranalysesyteme GmbH. Thermogravimetric analysis the ask was cooled to 80 C. And 1.6405 g (5 mmol) of 1-bro-
(TGA) of the polymers were performed on a Mettler TGA/ mododecane (498.4 mg, 2 mmol) was carefꢀully added. The
SDTA851 thermogravimetric analysis instrument in a nitrogen reaction mixture was then heated to 190–195 C. The Cu(I) Cl/
atmosphere at a heating rate of 20 ꢀC minꢁ1 from 25 to 800 ꢀC. quinoline catalyst (0.5 mL) was injected into the reaction
Decomposition temperature (Td) in nitrogen was taken as the mixture. The resulting mixture was maintained at this temper-
temperature of 5% weight loss. Char yield (Cy) was calculated as ature for 17 h, aer which time, the color of reaction solution
ꢀ
the percentage of solid residue aer heating from 25 to 800 C became dark red, indicating that the potassium salt of M1 had
in owing nitrogen. The glass transition temperature (Tg) was almost gone into solution. Then the solution was poured into
determined with a Mettler DSC822 differential scanning calo- the water in the presence of some dilute HCl. The organic
rimetry (DSC) in owing nitrogen at a heating rate of 10 ꢀC compounds were extracted with DCM. The organic layer was
minꢁ1 from 25 to 350 C. The Tg value was taken at the inec- dried over Na2SO4 and concentrated in vacuo. The crude product
ꢀ
tion point. Cylic voltammetric experiments were carried out on was puried by column chromatography using n-hexane as the
an electrochemistry workstation with a BAS100W voltammetric eluent. 697.6 mg of brown product was obtained (yield: 81%).
analyzer. A three-electrode setup was performed in a dichloro- 1H-NMR (400 MHz, CDCl3) d 8.56 (dd, J ¼ 7.8, 1.5 Hz, 1H), 7.87–
methane containing 0.1
M
tetrabutylammonium hexa- 7.72 (m, 5H), 7.66 (d, J ¼ 8.3 Hz, 2H), 7.43 (d, J ¼ 11.5 Hz, 1H),
uoroborate as the supporting electrolyte, used employing 4.36–4.25 (m, 2H), 1.91 (dt, J ¼ 14.9, 7.6 Hz, 2H), 1.42–1.21 (m,
platinum working and counter electrodes and an Ag/Ag+ refer- 18H), 0.87 (t, J ¼ 6.8 Hz, 3H). 13C-NMR (101 MHz, CDCl3) d
ence electrode (containing 0.01 M silver nitrate in dichloro- 158.98 (s), 146.24–146.04 (m), 143.42 (s), 134.90 (s), 134.53 (s),
methane). Potentials were recorded relative to the ferrocene/ 132.73 (s), 131.36 (s), 130.14 (s), 128.97 (s), 128.35 (s), 127.31 (s),
ferrocenium (Fc/Fc+) redox couple which occurs at a value of 126.50–126.16 (m), 125.81 (s), 124.84 (s), 51.51 (s), 31.94 (s),
+0.07 V under these conditions. LUMO and HOMO energies 29.56 (dd, J ¼ 16.3, 11.9 Hz), 28.66 (s), 26.83 (s), 22.71 (s), 14.15
were calculated from the onset of the rst reduction peak (s). MALDI-TOF [M + H]+: calc. As: C56H68N4O2S; 861.25 (m/z).
assuming a formal potential of Fc/Fc+ of ꢁ4.80 eV relative to Found: 861.46 (m/z).
vacuum level (scan rate 50 mV sꢁ1). The optical band gap was
calculated from measured at the onset of absorption. Quantum
yield measurements of the polymers, dissolved in organic
General synthesis of poly(phthalazinone ether)s by classical
nucleophilic aromatic substitution reactions
solvent, were performed using quinine sulfate (quantum yield ¼
0.546, excited at 346 nm, in 0.1 N H2SO4) as standards.24 DFT A typical synthetic procedure of PDSK82 was described as
calculations were performed using the Gaussian 09W program follows (shown in Scheme 3). A mixture of M1 (1.0852 g,
at the B3LYP level with a 6-31G(d,p) basis set.23
2 mmol), M3 (0.4594 g, 1.6 mmol), M4 (0.0087 g, 0.4 mmol),
anhydrous Cs2CO3 (0.9775 g, 3 mmol), 20 mL HMPA and 40 mL
toluene was placed in a 100 mL three-necked round-bottomed
ask equipped with a mechanical stirrer, a nitrogen inlet and
Synthesis of monomers and polymers
4,40-(thiophene-2,5-diylbis(4,1-phenylene))bis(phthalazin- outlet. The reaction mixture was constantly stirred and heated
1(2H)-one) (M1). To a mixture of 2,5-bis(tributylstannyl)thio- to 142 ꢀC for 3 h, maintained at this temperature for 4 h to
phene (66.22 mg, 0.1 mmol) and 4-(4-bromophenyl)phthalazin- remove water produced during the reaction. Aer complete
1(2H)-one (60.22 mg, 0.2 mmol) in N-methyl-2-pyrrolidone dehydration, the reaction temperature was increased to 190–
(NMP) 10 mL was added PdCl2(PPh3)2 (2.8 mg, 0.4% mmol) 195 ꢀC (oil bath) and the toluene was distilled. The resulting
ꢀ
under a N2 atmosphere. The mixture was stirred at 110 C for mixture was maintained at this temperature for 17 h. Then the
42 h. A green precipitate was ltered. The resulting solid was reaction mixture was slowly poured into sufficient ethanol at the
washed with hot N,N-dimethyl acetamide (DMAc), NMP and presence of hydrochloric acid in drops. The crude polymer was
water, and subjected to Soxhlet extraction successively with washed for six times with hot distilled water to remove inor-
ethanol and dried under vacuum. 31.0 mg of greyish-green ganic salts. The dried polymer was puried by dissolving in
product was obtained (yield: 75%). Anal. calcd for NMP, being ltered through a 0.45 mm Teon micro lter
C
32H20N4O2S: C, 73.27; H, 3.84; N, 10.68; S, 6.11. Found: C, before pouring into ethanol, and subsequently washed six times
68.73; H. 3.81; N, 10.06; S, 5.88. with hot deionized water. The polymers were puried by Soxhlet
4,40-(thiophene-2,5-diylbis(4,1-phenylene))bis(2-dodecyl- extraction with ethanol and acetone sequentially. The puried
phthalazin-1(2H)-one) (M2).
A
50 mL, 3-necked round- polymer was dried at 120 ꢀC under vacuum for 24 h. The
bottomed ask equipped with a Dean–Stark trap, condenser, product was obtained in yield 74% (1.11 g). 1H-NMR (400 MHz,
inert gas inlet, magnetic stirrer, was charged with M1 (524.6 mg, CDCl3) d 8.59 (s, 1H), 8.12–7.92 (m, 4H), 7.92–7.74 (m, 5H), 7.67
1
mmol), cesium carbonate (325.82 mg,
1
mmol), (s, 2H), 7.43 (t, J ¼ 13.5 Hz, 1H). 13C-NMR (101 MHz, CDCl3) d
This journal is © The Royal Society of Chemistry 2015
RSC Adv., 2015, 5, 30445–30455 | 30447

View Article Online
RSC Advances
Paper
175.04 (s), 158.72 (s), 147.79 (s), 145.81 (s), 143.22 (s), 139.54 (s), M1 was obviously precipitated out from the reactive medium
135.14 (s), 133.67 (s), 132.03 (s), 130.33 (d, J ¼ 40.2 Hz), 130.08 NMP at 110 ꢀC. Unconverted reactants and some by-products,
(s), 129.59 (s), 129.09 (s), 128.67 (s), 128.06 (d, J ¼ 28.3 Hz), detected by HPLC-MS in NMP (Fig. S11†), were removed by
127.92–127.65 (m), 126.84 (s), 125.60 (t, J ¼ 34.6 Hz), 124.98 (s). successively treated with hot DMAC, NMP and water, and then
GPC: Mn ¼ 16.5 kDa, Mw ¼ 54.5 kDa, PDI ¼ 3.3.
Soxhlet extracted with ethanol for 24 h. Unfortunately, the
Others copolymers with different monomers were prepared sufficient characterizations of M1 (1H-NMR, 13C-NMR and
using the similar procedures as outlined above and character- MALDI-TOF) were hard to carry out owing to its insolubility in
ized as follow.
organic solvent. Due to large molecular conjugated structure,
PDS. Yellow product. Yield: 73%. 1H-NMR (400 MHz, CDCl3) d melting point (measured by DSC) of M1 (Fig. S10†) was not
8.59 (s, 1H), 8.11–7.90 (m, 4H), 7.88–7.72 (m, 4H), 7.67 (s, 2H), 7.52 detected from 30 to 350 ꢀC. And only elemental analysis and
(d, J ¼ 1.7 Hz, 1H), 7.41 (d, J ¼ 7.5 Hz, 1H). 13C-NMR (101 MHz, Fourier transform infrared spectrometry (Fig. S8†) were obtained.
CDCl3) d 175.09 (s), 158.74 (s), 147.82 (s), 145.86 (s), 143.20 (s),
For the detailed characterizations of M1, its long-chain alkyl
139.51 (s), 135.11 (s), 133.67 (s), 132.10–131.90 (m), 130.13 (s), substituted derivative M2 was synthesized. As we expected, M2
129.39 (s), 128.64 (s), 128.21 (s), 127.24–126.62 (m), 125.92 (s), has excellent solubility in organic solvent. Thus 1H-NMR,
125.07 (s). GPC: Mn ¼ 24.4 kDa, Mw ¼ 92.7 kDa. PDI ¼ 3.8.
13C-NMR (Fig. S1†) and MALDI-TOF (Fig. S7†) of M2 were
PDSK55. Black product. Yield: 79%. Calc. for easily measured. The 1H-NMR, 13C-NMR spectra of M2 obtained
C
455H300N40O30S15: C, 74.98; H, 4.15; N, 7.69; O, 6.59; S, 6.60. all displayed the expected signals with no discernible peaks
Found: C, 67.61; H, 3.60; N, 6.54; S, 5.68.
corresponding to impurities. Thus the structure of M1 was
PDSKK82. Brown product. Yield: 79%. 1H-NMR (400 MHz, conrmed by the unambiguous spectral characterization of M2.
CDCl3) d 8.57 (s, 1H), 8.13–7.90 (m, 4H), 7.90–7.46 (m, 9H), 7.41 The optical electrochemical properties and quantum chemical
(s, 1H). 13C NMR (101 MHz, CDCl3) d 175.19–175.05 (m), 158.80 calculations (B3LYP/6-31G**) by Gaussian 09 package were also
(s), 145.90 (s), 143.31 (s), 139.78–139.51 (m), 135.46–135.05 (m), investigated as follows.
133.74 (s), 132.11 (s), 129.91 (d, J ¼ 48.9 Hz), 129.63–129.43 (m),
Molecular orbital computation. For further understanding
129.17 (s), 128.51 (d, J ¼ 48.1 Hz), 127.99–127.84 (m), 127.55 (s), electronic structure of M1, quantum chemistry calculations by
126.93 (s), 125.60 (t, J ¼ 44.9 Hz), 111.18 (s). GPC: Mn ¼ 15.5 DFT (B3LYP/6-31G**) method were performed (the hexyl group
kDa, Mw ¼ 60.5 kDa, PDI ¼ 3.9.
replaced the dodecyl group). As shown in Fig. 2, due to the
PDSKK55. Black product. Yield: 74%. Calc. for electron-withdrawing group such as C]N and C]O in phtha-
C
480H320N40O35S15: C, 74.98; H, 4.20; N, 7.29; O, 7.28; S, 6.25. lazinone group, the LUMO orbits of M2 are delocalized along
Found: C, 67.39; H, 5.54; N, 7.24; S, 5.54.
phthalazinone–thiophene axis and mainly localized at the
PDNS. Yellow product. Yield: 70%. 1H-NMR (400 MHz, phthalazinone core. While its HOMO orbits are delocalized on
CDCl3) d 8.80 (t, J ¼ 9.7 Hz, 1H), 8.59 (d, J ¼ 9.9 Hz, 2H), 7.96– the thiophene core because of electron-rich of thiophene unit. If
7.70 (m, 7H), 7.69–7.48 (m, 4H), 7.36 (d, J ¼ 4.1 Hz, 1H). 13C M2 is excited, its electrons will transfer from the thiophene core
NMR (101 MHz, CDCl3) d 175.21 (s), 159.44 (s), 147.99 (s), 144.35 to phthalazinone–thiophene core. The calculated HOMO–
(s), 143.38 (s), 137.30 (s), 135.29 (s), 133.84 (d, J ¼ 27.4 Hz), LUMO gap of M2 was found to be 3.64 eV. In addition, a couple
132.35 (s), 130.48 (d, J ¼ 31.8 Hz), 130.02 (s), 129.60 (s), 129.16 of sensitive and reversible redox peaks were obtained from the
(d, J ¼ 31.3 Hz), 128.35 (d, J ¼ 51.0 Hz), 128.09 (s), 128.09 (s), cyclic voltammograms (CV) (details in Fig. S9†). The CV-
127.26 (s), 125.94 (s), 124.38 (d, J ¼ 37.8 Hz). GPC: Mn ¼ 24.6 calculated HOMO and LUMO were ꢁ5.87 eV and ꢁ2.79 eV,
kDa, Mw ¼ 91.0 kDa, PDI ¼ 3.7.
respectively. This indicates that M1 has the strong electron-
PDNK. Brown product. Yield: 74%. 1H-NMR (400 MHz, withdrawing ability and can be used as acceptor to build
CDCl3) d 8.65 (s, 1H), 8.21 (s, 1H), 8.04–7.86 (m, 5H), 7.73 (t, J ¼ conjugated polymers.
13.4 Hz, 7H), 7.57 (s, 2H), 7.38 (s, 1H). 13C NMR (101 MHz,
Optical properties. UV/vis absorption spectra of M2 were
CDCl3) d 171.58–171.03 (m), 155.08 (s), 144.15 (s), 142.17 (s), studied in different solvent (Fig. 3). The UV/vis absorption of M2
139.58 (s), 136.54–136.11 (m), 135.89 (s), 131.50 (s), 130.03 (s), showed slight bathochromic shi effect with the increase in the
128.39 (s), 126.68 (d, J ¼ 40.2 Hz), 126.44 (s), 125.95 (s), 125.45
(s), 125.02 (s), 124.42 (d, J ¼ 28.3 Hz), 124.28–124.01 (m), 123.20
(s), 121.96 (t, J ¼ 34.6 Hz), 121.34 (s), 121.09–120.82 (m). GPC:
Mn ¼ 16.5 kDa, Mw ¼ 59.4 kDa PDI ¼ 3.6.
Results and discussion
Monomers
Monomers synthesis. For designing “non-ether bond” poly-
(phthalazinone ether) synthesized by classical nucleophilic
aromatic substitution reactions, the monomer M1 was prepared
by Stille coupling as showed in Scheme 2. The reactive monomer
2,5-bis(tributylstannyl) thiophene 1 was synthesized as literature
reported.25 During Stille coupling reaction, the target monomer replaced the dodecyl group).
Fig. 2 Calculated LUMO and HOMO orbits for M2 (the hexyl group
30448 | RSC Adv., 2015, 5, 30445–30455
This journal is © The Royal Society of Chemistry 2015

View Article Online
Paper
RSC Advances
Table 2 Synthetic data of copolymers
Polymer
Mn (kDa)
PDI
N% (cal/found)
Yielda (%)
PDS
24.4
16.5
—
15.5
—
3.8
3.3
—
3.9
—
7.73/7.74
7.75/7.49
7.69/6.54
7.53/8.47
7.29/7.24
6.79/7.47
6.16/6.54
73
74
79
79
74
70
74
PDSK82
PDSK55
PDSKK82
PDSKK55
PDNS
24.6
16.5
3.7
3.6
PDNK
a
Fig. 3 UV-vis absorption spectra for M2 in different solvent.
Isolated aer precipitation and purication.
polarity of solvents. The maximum absorption wavelength of
M2 in solution ranged from 345 nm to 353 nm, and its long
wavelength of the absorption tails reached to 393 nm to 413 nm,
respectively.
Polymer
Polymer synthesis. Ten polymers were then prepared by the
classical nucleophilic aromatic substitution reactions between
di-NH capped monomer M1 and various activated di-
halogenated compounds with the yield being 70–79%
(Table 2). A strong base (Cs2CO3) and strong polar, high boiling
solvent (hexamethylphosphoric triamide: HMPA) were used in
order to obtain high molecular polymers in our polymerization
system. The number-average moleculars (Mn) of the obtained
polymers were varying from 15.0 kDa to 24.6 kDa. Their poly-
dispersity index (PDI), and N% (the N content of the polymers,
measured by elemental analysis) are summarized in Table 2.
The values of N% showed good agreement between calculated
and measured. All resulting polymers had a much broader
distribution of molecular weight, presumably due to mono-
mer's (M1) poor solubility to lead to the rather high viscosity of
the reaction mixture and make the heating and mixing of the
reactants uneven.27 All polymers' solubility in organic solvents
are shown in Table S1.† PDSK55 and PDSKK55 were insoluble in
organic solvent due to the high content of linear rod-like
structure (ketone groups) in the polymer's chain. PDK and
PDKK, prepared from 4,40-diuoro diphenylmethanone
(monomer M4) or 4,40-diuorobenzoyl benzene (monomer M5),
respectively, were precipitated during polymerization. However,
naphthalene series of polymers (PDNS and PDNK) had better
solubility in organic solvent than phenyl series of polymers.
This can be explained by the optimized molecular geometries
obtained by DFT as shown in Table 4. The big twist angle q3 in
the main chain of naphthalene series of the polymers results in
its excellent solubility in organic solvent.
Fluorescence spectra of M2 in different solvent are shown in
Fig. 4. M2 showed two emission peaks, and bathochromic shi
effect was also observed with the increase in the polarity of
solvents. Its second peak intensity increased with the polarity of
solvents. In NMP, the emission peak became broadened by virtue
of intermolecular charge transfer (ICT) effect of donor–acceptor
structure (phthalazinone–thiophene). In addition, M2 exhibited
a strong emissivity (Table 1) and was different from other oli-
gothiophenes' and polythiophenes' weak-to-moderate emitters,
due to the heavy atom effect of sulfur to enhance the intersystem.
We suppose that intercrossed-excited-state (LE and CT) effect of
M2 lead to the strong blue emissivity, which was conrmed by
the DFT calculation below (Table 4) of the obvious twist angle
between the phenyl, phthalazinone and thiophene units.26
The structures of the resulting polymers were analyzed using
1H-NMR (Fig. 5) and 13C-NMR. The single peak splitting and
shiing downeld at 8.59 ppm was attributed to the typical peri-
position signal of the phthalazinone, which is always used as
the reference signal to assign the other atom except PDNS. For
PDNS, the chemical shi of the peri-position proton in the
phthalazinone was shied to lower eld about 8.78–8.80 ppm
due to the sulfone group and naphthalene. The chemical shi
of the protons of the thiophene core appeared at about
7.40 ppm. The spectroscopic dates in Fig. 5 are in agreement
with the proposed structures.
Fig. 4 Emession spectra of M2 in different solvent.
Table 1 Fluorescence property of M2
Excitation
Emission
Solvent
wavelength (nm) wavelength (nm) PLQY
Chloromethane
Diethyl ether
n-Hexane
345
345
345
413.2, 430.4
407.6, 426.6
406.8, 426.0
420.4, 434.6
0.45
0.54
0.52
0.53
Furthermore, their 13C-NMR pictures are shown in Fig. 6. A
detailed chemical shi assignment of our copolymer
Methyl-2-pyrrolidinone 345
This journal is © The Royal Society of Chemistry 2015
RSC Adv., 2015, 5, 30445–30455 | 30449

View Article Online
RSC Advances
Paper
Fig. 5 1H-NMR spectra of polymers.
Fig. 7 FTIR spectra of the different copolymers in powder.
Fig. 6 13C-NMR spectra of polymers.
in Fig. 7. A asymmetric stretching vibration band at 1300 cmꢁ1
to 1350 cmꢁ1 and a symmetrical stretching vibration band at
1120 cmꢁ1 to 1160 cmꢁ1 from O]S]O stretch were observed
for PDS, PDSK and PDSKK polymers containing sulfone
groups, also for PDNS. The ketone groups of the polymers
could be conrmed by C–C stretch on C]O group at
products are gured out. It is revealed that the PDNS and
PDNK can be clearly distinguished from other polymers. For
the PDSK82 and PDSKK82 copolymers, their different signals
from PDS were attributed to M2 and M3 units, which is
successfully in agreement with the copolymer structures as we
designed.
1260 cmꢁ1
.
Other chemical shis of 1H-NMR and 13C-NMR spectra were
also found to be well in accord with the chemical structures of
the polymers, as listed in Experimental sections.
Thermal properties. Thermal stability of all polymers was
investigated by using thermogravimetric analysis (TGA) with a
heating ramp rate of 20 ꢀC minꢁ1 under a N2 atmosphere
(Fig. S12†). The 5% weigh loss temperatures (Td5%) of all soluble
polymers (aer puried) were above 489 ꢀC aer removing a
The structure of the polymers obtained was also conrmed
by Fourier transform infrared (FTIR) spectroscopy as depicted
30450 | RSC Adv., 2015, 5, 30445–30455
This journal is © The Royal Society of Chemistry 2015

View Article Online
Paper
RSC Advances
Table 3 Thermal properties of copolymers
Polymers
Tg (ꢀC)
T5% (ꢀC)
Cy (%)
PDS
>350
326
288
272
261
267
213
—
492
495
441
489
460
496
495
403
63
67
74
68
74
72
75
33
PDSK82
PDSK55
PDSKK82
PDSKK55
PDNS
PDNK
M1
small amount of residual water, HMPA and NMP below 250 ꢀC,
demonstrating the excellent thermal stability of these polymers.
Due to the insolubility of PDSK55 and PDSKK55, they were not
puried (only Soxhlet extracted by ethanol) in the result that the
Td5% of PDSK55 and PDSKK55 was only 441 and 460 ꢀC because
of the residual low molecular weight oligomers. In addition,
naphthalene series of polymers exhibited higher char yield
(72%–75%) than phenyl series of polymers (63%–68%). The
char yield of the investigated polymers in the nitrogen atmo-
ꢀ
sphere was in the range of 63–75% at 800 C, conrming their
excellent thermal stability.
Differential scanning (DSC) was implemented at a scan rate
ꢁ1
ꢀ
of 10 C min to investigate the phase transition of all poly-
mers, as shown in Fig. S14† and Table 3. The glass transition
temperatures (Tg) of these polymers were recorded in exceed
213 ꢀC. Among the investigated polymers, PDS displayed the
highest Tg value exceed 350 ꢀC. The reasonable explains are that
the strongest interaction of the polymer chains of PDS with the
introduction of polar sulfone groups to hinder the movement of
polymer chains. In addition, the Tg values of the detected
polymers decreased gradually with the increasing content of
ketone groups in the main chain of the polymers for the above
reasons.28
Molecular orbital computation. To receive the information
on the electronic states of the synthesized polymers, we per-
formed the theoretical calculation using density-functional
theory (DFT) at the B3LYP/6-31G(d,p)//B3LYP/6-31G(d,p)
(Fig. 8). PDS and PDSK82 have better extension of the conju-
gated system through the polymer main chains than
PDSKK82, PDNS and PDNK. Meanwhile, a big twist angles of
di-ketone and naphthalene unit in the polymer backbone
resulted in weak extension of the conjugated system. This
leads to the limitation of the conjugation effects of PDSKK82,
PDNS and PDNK into only one segment. Also, the LUMO
electrons clouds of the polymers containing ketone groups
were distributed at ketone groups, which are different from
those of PDS and PDNS containing sulfone groups. That
indicates that N–H side in phthalazinone unit has excellent
conjugated effect.
Fig. 8 Calculated dipole moment, HOMO and LUMO orbitals of
polymers. The black arrow shows the magnitude and direction of the
dipole moment.
q3 increased with the increasing steric hindrance from naph-
thalene with benzene rings (phenyl series of polymers) to
naphthalene with naphthalene rings (naphthalene series of
polymers). Also the dipole moment of the polymers is listed out
in Fig. 8. The inuence on optical properties and electro-
chemical properties in more details would be discussed as
follows.
The dihedral angles (deg) along the conjugated backbone for
the optimized molecular geometries are also shown in Table 4.
The dihedral angles between benzene and thiophene rings (q1)
were 19–24ꢀ.Comparing with q2 ¼ 41–44ꢀ, the naphthalene
linked with benzene rings increased steric hindrance. Similarly,
This journal is © The Royal Society of Chemistry 2015
RSC Adv., 2015, 5, 30445–30455 | 30451

View Article Online
RSC Advances
Paper
Table 4 Dihedral angles (deg) along the conjugated backbone for the
optimized molecular geometries obtained by DFT evaluated at B3LYP/
6-31G(d,p) level
Polymer
q1 (deg)
q2 (deg)
q3 (deg)
PDS
22.7
22.9
23.4
19.2
24.6
43.4
42.8
44.4
41.1
43.2
29.3
28.9
30.2
60.0
62.2
PDSK82
PDSKK82
PDNS
PDNK
Fig. 10 Emission spectra of polymer in NMP (a) and thin film (b).
Table 5 Optical properties of polymers
lmax (nm)
lem (nm)
Polymers Solution Film
Solution Film Stokes shi (nm) PLQY
Fig. 9 UV-vis absorption spectra for the polymers in NMP and thin
film.
PDS
PDSK82 356
PDSKK82 349
PDNS
PDNK
348, 354 402
448
443
443
496 94
493 87
496 94
501 86
495 88
0.20
0.28
0.17
0.19
0.04
366
<350
341, 350 365, 377 436
346 364 434
Optical properties. The UV-vis absorption and uorescence
spectra of all polymers were recorded in NMP at a concentration
of 1 mg mLꢁ1 and in drop-coated thin lm. The UV-vis absorp-
tion and uorescence spectra are shown in Fig. 9 and 10. All data
are summarized in Table 5.
nucleophilic displacement polycondensation reaction. In the
solid state, the absorption spectra of all polymers were broad-
ened; red shied and exhibited a distinguishable structure.
Especially, the absorption spectra for sulfone-containing poly-
mers broadened and red shied more than the polymers con-
taining ketone and di-ketone segments. This is attributed to
strong chain interaction of sulfone group than that of ketone
group. Moreover, q3 ¼ 29–30ꢀ for phenyls series of polymers was
smaller than q3 ¼ 60–62ꢀ for naphthalene series of polymers.
Phenyl series of polymers like PDS have stronger intermolecular
interaction than naphthalene series of polymers like PDNS. So
the maximum absorption wavelength of PDS in lm state was
402 nm, longer than that of PDNS (365 nm, 377 nm). All these
above observations are usually associated with possible charge
transport applications.
The maximum absorption wavelength of PDS in solution was
348 nm (354 nm shoulder peak), which is 8 nm blue-shied
relative to PDSK82 (356 nm) and 1 nm blue-shied relative to
PDSKK82 (349 nm). Their dihedral angles had no obvious
change. So the blue shi of absorption for PDS could be
ascribed to weaker electron-withdrawing property of ketone
group in PDSK82 and PDSKK82. From the other side, the ketone
group in PDSK82 and PDSKK82 has stronger electron-donating
ability to DHPZ core. This phenomenon also appeared for PDNS
and PDNK. Moreover, due to the big dihedral angle of two
naphthalene groups (q3 in Table 4), the maximum absorption
wavelength of PDS and PDSK82/KK82 (phenyl series) appeared
at longer wavelength than PDNS and PDNK (naphthalene
series). The maximum absorption peaks of the most polymers
exhibited red shi effect than M2 (346 nm), indicating that the
conjugated length of the polymers could be prolonged along the
polymeric backbones due to cutting off the ether bond in the
main chain of the polymers although prepared by classical
Generally, oligo-, polythiophenes and heteroaromatic poly-
mers are weak-to-moderate emitters owing to the heavy atom
effect of sulfur enhancing the intersystem crossing29 and the
heterocyclic compounds with nitrogen heteroatoms spin-
30452 | RSC Adv., 2015, 5, 30445–30455
This journal is © The Royal Society of Chemistry 2015

View Article Online
Paper
RSC Advances
forbidding n–p*. As a surprise, herein we observed that PDSK82
(PLQY ¼ 28%) containing fused thiophene ring and nitrogen-
heterocyclic structure exhibited a strong photoluminescence,
higher than PDS (PLQY ¼ 20%) and PDSKK82 (PLQY ¼ 17%).
We speculate that PDSK82 containing ketone group has
different localization manners between LUMO and HOMO than
PDS and PDSKK82 in the result of better emission originated
from the intermolecular charge transfer (ICT) states.26,29
However, PDSKK82 and PDNK containing di-ketone group
exhibited weak emissive. The reason can be found that the two
ketone groups interrupt their conjugated structure in the main
chain to hinder the electron transport along the polymer
backbone in Fig. 8. It is worth noting that due to the strong
torsion between phenyl–phthalazinone core and naphthalene
in M6 and M7, phenyl series of polymers show longer wave-
length emission than naphthalene series of polymers in NMP.
Electrochemical properties. The electrochemical properties
of the synthesized polymer are summarized in Table 6. The
frontier molecular orbits determined by CV (Fig. S14†) is
compared to the predict energies using DFT with a 6-31G** basis
set as shown in Fig. 11. M2 showed two reversible oxidation
processes and one irreversible redox processes during negative
scan. Its energy levels were estimated to be ꢁ2.79 eV for the
LUMO and ꢁ5.87 eV for the HOMO. And its energy band was
3.08 eV. All polymers derived from M2 exhibited a narrower
electrical energy band than M2, indicating di-NH end-caped
monomer could prolong conjugated length in the polymeric
backbones. In addition, weak CT effect of sulfone and ketone
groups resulted in the broad electrical energy band of all poly-
mers than most conjugate D–A polymers.30 PDSK82 showed the
most narrow optical energy band among these polymers. The
reasons could be explained by DFT calculation in Fig. 8. It has
been proved that a molecule having different localization
manners between the frontier orbits oen exhibits the broad
emission in the long wavelength region originated from the
intramolecular charge transfer (ICT) states. The optical energy
band of ve soluble polymers were varies from 2.73 eV to 2.88 eV.
As showed in Fig. 11, the sulfone-containing polymer has
deeper LUMO level than the ketone-containing analogue
because of the strong electron-withdrawing ability of sulfone
group. For instance, ꢁ2.75 eV for the LUMO of PDS was deeper
than ꢁ2.64 eV (PDSK82) and ꢁ2.68 eV (PDSKK82). The electron
energy band of naphthalene series of polymers like PDNS
(2.36 eV) and PDNK (2.45 eV) was smaller than that of phenyl
series of polymers like PDS (2.76 eV), PDSK82 (2.71 eV) and
Fig. 11 Frontier molecular orbital energy levels as predicted by DFT
calculation with a 6-31g** basis set and CV.
PDSKK82 (2.67 eV). However, PDNS and PDNK containing
naphthalene segments showed the big dihedral angle in the
polymer backbone, resulting in weak extension of the conju-
gated system. The CV measurement exhibited the narrower
band gap for PDNS and PDNK than that value for other poly-
mers with better co-planarity. As the naphthalene group has
better electron-donating ability than phenyl, and the sulfone
group has electron-drawing ability than ketone group, a strong
donor–acceptor system also led to narrower band gap. We
deduce that the latter plays a major factor under such
circumstances.
From the onset of oxidation and reduction peaks the HOMO
and LUMO values as well as the electrochemical band gaps were
calculated. As shown in Table 6, the electrochemical band gap
values calculated by CV were similar to the values predicted by
DFT. The HOMO energy levels of most polymers were lower
than their air oxidation (ca. ꢁ5.27 eV) indicating good air
stability and a higher Voc in PSCs.31 Moreover, due to the low
HOMO energy level of the polymers, M1 could be a potential
acceptor to build conjugated polymers for solar cells.
Physical properties. X-ray diffraction (XRD) measurement
was used to investigate the physical properties of the polymers
in thin lms. Fig. 12 shows the XRD patterns of the ve poly-
mers casted from NMP. Obviously, no sensitive peaks were
found at the region from 5 to 60ꢀ, indicating that they possess
Table 6 Electrochemical data of polymers
Polymer
LUMO (eV)
HOMO (eV)
Eg (eV)
PDS
PDSK82
ꢁ2.75a ꢁ2.11b ꢁ5.51a ꢁ5.60b 2.76a 2.82c 3.49b
ꢁ2.64
ꢁ2.05
ꢁ2.23
ꢁ2.09
ꢁ2.32
ꢁ5.35
ꢁ5.36
ꢁ5.16
ꢁ5.27
ꢁ5.55
ꢁ5.59
ꢁ5.59
ꢁ5.55
2.71
2.68
2.36
2.54
2.73
2.86
2.75
2.88
3.50
3.36
3.50
3.23
PDSKK82 ꢁ2.68
PDNS
PDNK
ꢁ2.80
ꢁ2.73
a
b
Calculated by cyclic voltammograms. Calculated by Gaussian 09.
Calculated by UV-vis absorption spectra.
c
Fig. 12 The XRD spectra of polymer films.
RSC Adv., 2015, 5, 30445–30455 | 30453
This journal is © The Royal Society of Chemistry 2015

View Article Online
RSC Advances
Paper
¨
some amorphous features without crystalline domains. Only a
widely insensitive diffraction peaks (17ꢀ–30ꢀ) for p–p stacking
of PDS, PDSK82 and PDNK were distinguished. Heeger and co-
workers have put forth that self-assembly could be driven by the
orientation and strength of the molecular dipole moment. As
pointed out in Fig. 8, we can therefore hypothesize that the
change of the molecular dipole moment results in a different
intermolecular packing manner. Furthermore, it has been
demonstrated experimentally and computationally that PDSK82
(dipole moment, m ¼ 5.0669 D) are more advantageous to the
pꢁp stacking than PDSKK82 (dipole moment, m ¼ 2.9069 D).
The different intensity of diffraction peaks (17ꢀ–30ꢀ) of PDSK82
and PDSKK82 can clearly be visible in Fig. 12. However, M6 with
high dipole moment (m ¼ 4.0094 D) had no obvious widely
insensitive diffraction peaks. That can be attributed to highly
twisted backbone of PDNS (Fig. 8).32 In addition, the non-
crystalline feature of polymers shows they could be favorable
for their PLED applications.33
K. Mullen, Prog. Polym. Sci., 2013, 38, 1832–1908; (c) J. You,
L. Dou, Z. Hong, G. Li and Y. Yang, Prog. Polym. Sci., 2013,
38, 1909–1928; (d) A. Sui, X. Shi, H. Tian, Y. Geng and
F. Wang, Polym. Chem., 2014, 5, 7072–7080; (e) C. Gao,
L. Wang and X. Li, Polym. Chem., 2014, 5, 5200–5210.
´
2 (a) J. Hassan, M. Sevignon, C. Gozzi, E. Schulz and
M. Lemaire, Chem. Rev., 2002, 102, 1359–1470; (b)
P. Espinet and A. M. Echavarren, Angew. Chem., Int. Ed.,
2004, 43, 4704–4734; (c) R. Jana, T. P. Pathak and
M. S. Sigman, Chem. Rev., 2011, 111, 1417–1492; (d) B. Liu,
B. Qiu, X. Chen, L. Xiao, Y. Li, Y. He and Y. Zou, Polym.
Chem., 2014, 5, 5002–5008; (e) G. Zhang, J. Guo, J. Zhang,
P. Li, J. Ma, X. Wang and L. Qiu, Polym. Chem., 2015, 6,
418–425; (f) L. Wang, D. Cai, Z. Yin, C. Tang, S. C. Chen
and Q. Zheng, Polym. Chem., 2014, 5, 6847–6856.
3 J. Wang, Y. Gao, A. R. Hlil and A. S. Hay, Macromolecules,
2008, 41, 298–300.
4 N. Berard and A. S. Hay, Polym. Prepr. (Am. Chem. Soc., Div.
Polym. Chem.), 1993, 34, 148–149.
5 (a) S. Yoshida and A. S. Hay, Macromolecules, 1995, 28, 2579–
2581; (b) S. Yoshida and A. S. Hay, Macromolecules, 1997, 30,
2254–2261.
6 X. Li and A. S. Hay, J. Polym. Sci., Part A: Polym. Chem., 2007,
45, 975–979.
Conclusions
In summary, we have designed, synthesized, and characterized
a new di-NH capped monomer and its polymers prepared by
classical nucleophilic aromatic polymerization. Compared with
commercial PEEK, poly(aryl ethers)s and traditional poly-
(phthalazinone ether)s synthesized by the same polymerization
method, these non-ether bond polymers show remarkable
photoelectric properties. To our knowledge, this is the rst
report that the polymers containing phthalazinone–thiophene
structure derived from classical nucleophilic aromatic poly-
merization to apply in the optoelectronic polymer materials.
The polymers exhibit highly thermostability and blue-
uorescence property. The optical band gap and HOMO
7 S. J. Wang, Y. Z. Meng, A. R. Hlil and A. S. Hay,
Macromolecules, 2004, 37, 60–65.
8 (a) L. Cheng, X. G. Jian and S. Z. Mao, J. Polym. Sci., Part A:
Polym. Chem., 2002, 40, 3489–3496; (b) L. Cheng and
X. G. Jian, J. Appl. Polym. Sci., 2004, 92, 1516–1520.
9 (a) J. Y. Wang, X. G. Jian and S. D. Xiao, Chin. Chem. Lett.,
2001, 12, 593–594; (b) J. Y. Wang, G. X. Liao, C. Liu and
X. G. Jian, J. Polym. Sci., Part A: Polym. Chem., 2004, 42,
6089–6097.
energy levels are varying from 2.36 eV to 2.76 eV and ꢁ5.16 eV to 10 Y. R. Gao, J. Y. Wang, C. Liu and X. G. Jian, Chin. Chem. Lett.,
ꢁ5.51 eV, respectively. The effect of ketone/di-ketone, sulfone 2006, 17, 140–142.
group, phenyl and naphthalene groups in the main chain of the 11 X. Li, Y. Gao, Q. Long and A. S. Hay, J. Polym. Sci., Part A:
resulting polymers on the optical properties were investigated Polym. Chem., 2014, 52, 1761–1770.
in details. On the basis of our results, fused di-NH monomer 12 (a) S. Xiao, J. Wang, K. Jin, X. Jian and Q. Peng, Polymer,
and classical nucleophilic displacement reaction method can
narrower the band gap and adjust the wavelength of the lumi-
nescence. Further studies on the polymers based on di-NH
capped monomer by classical nucleophilic aromatic polymeri-
zation are under way.
2003, 44, 7369–7376; (b) Y. Song, J. Wang, G. Li, Q. Sun,
X. Jian, J. Teng and H. Zhang, Polymer, 2008, 49, 724–731;
(c) L. M. Dong, G. X. Liao, C. Liu, S. S. Yang and X. G. Jian,
Surf.Rev. Lett., 2008, 15, 705–709.
13 (a) Y. Dai, X. Jian, S. Zhang and M. D. Guiver, J. Membr. Sci.,
2001, 188, 195–203; (b) P. Y. Qin, X. J. Hong, M. N. Karim,
T. Shintani, J. D. Li and C. X. Chen, Langmuir, 2013, 29,
4167–4175.
Acknowledgements
The present research was nancially supported by National 14 W. Qi, C. Lu, P. Chen, L. Han, Q. Yu and R. Xu, Mater. Lett.,
Natural Science Foundation of China (no. 21074017 and 2012, 66, 239–241.
51273029). The authors acknowledge the High Performance 15 D. Xing, S. Zhang, C. Yin, B. Zhang and X. Jian, J. Membr. Sci.,
Computing Centre of Dalian University of Technology for
2010, 354, 68–73.
providing computational resources which have contributed to 16 J. Pan, K. Li, S. Chuayprakong, T. Hsu and Q. Wang, ACS
the research results.
Appl. Mater. Interfaces, 2010, 2, 1286–1289.
17 (a) X. Ma, C. Zhang, G. Xiao, D. Yan and G. Sun, J. Polym. Sci.,
Part A: Polym. Chem., 2008, 46, 1758–1769; (b) H. G. Chen,
S. J. Wang, M. Xiao and Y. Z. Meng, J. Power Sources, 2007,
165, 16–23.
Notes and references
1 (a) G. Yu, J. Gao, J. C. Hummelen, F. Wudl and A. J. Heeger,
Science, 1995, 270, 1789; (b) X. Guo, M. Baumgarten and
30454 | RSC Adv., 2015, 5, 30445–30455
This journal is © The Royal Society of Chemistry 2015

View Article Online
Paper
RSC Advances
18 (a) H. Zhang and B. Tieke, Polym. Chem., 2014, 5, 6391–6406; 24 C. A. Heller, R. A. Henry, B. A. McLaughlin and D. E. Bliss,
(b) Z. G. Zhang and J. Wang, J. Mater. Chem., 2012, 22, 4178–
J. Chem. Eng. Data, 1974, 19, 214–219.
4187.
25 X. Guo and D. W. Mark, Org. Lett., 2008, 10, 5333–5336.
19 V. A. Naumov, S. Samdal, A. V. Naumov, S. Gundersen and 26 W. Li, D. Liu, F. Shen, D. Ma, Z. Wang, T. Feng and Y. Ma,
H. V. Volden, Russ. J. Gen. Chem., 2005, 75, 1956–1961. Adv. Funct. Mater., 2012, 22, 2797–2803.
20 (a) A. Pron and M. Leclerc, Prog. Polym. Sci., 2013, 8, 1815– 27 (a) L. Fang, Y. Zhou, Y. X. Yao, Y. Lee, W. Y. Diao,
1831; (b) X. Guo, A. Facchetti and T. J. Marks, Chem. Rev.,
2014, 114, 8943–9021.
21 T. C. Chao, Y. T. Lin, C. Y. Yang, T. S. Hung, H. C. Chou,
C. C. Wu and K. T. Wong, Adv. Mater., 2005, 17, 992–996.
A. L. Appleton, R. Allen, J. Reinspach, S. C. B. Mannsfeld
and Z. N. Bao, Chem. Mater., 2013, 25, 4874; (b) Z. Zhao,
F. Zhang, Y. Hu, Z. Wang, B. Leng, X. Gao, C. Di and
D. Zhu, ACS Macro Lett., 2014, 3, 1174–1177.
22 (a) T. Yokozawa and A. Yokoyama, Chem. Rev., 2009, 109, 28 G. P. Yu, C. Liu, J. Y. Wang, T. S. Gu and X. G. Jian, Polym.
5595–5619; (b) P. David, B. Jan, G. T. Hendrik, W. W. Gary, Degrad. Stab., 2009, 94, 1053–1060.
D. Ernst-Ulrich, O. Edgar and R. Klaus, Polymers, High- 29 (a) I. F. Perepichka, D. F. Perepichka, H. Meng and F. Wudl,
Temperature. Ullmann's Encyclopedia of Industrial Chemistry,
Wiley-VCH, Weinheim, 2012, DOI: 10.1002/
14356007.a21_449.pub3.
Adv. Mater., 2005, 17, 2281; (b) J. A. Schneider, A. Dadvand,
W. Wen and D. F. Perepichka, Macromolecules, 2013, 46,
9231–9239.
23 M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, 30 X. Wang, L. Zhao, S. Shao, J. Ding, L. Wang, X. Jing and
M. A. Robb, J. R. Cheeseman, G. Scalmani, V. Barone, F. Wang, Macromolecules, 2014, 47, 2907–2914.
B. Mennucci, G. A. Petersson, H. Nakatsuji, M. Caricato, 31 (a) B. C. Thompson, Y. G. Kim and J. R. Reynolds,
X. Li, H. P. Hratchian, A. F. Izmaylov, J. Bloino, G. Zheng,
J. L. Sonnenberg, M. Hada, M. Ehara, K. Toyota,
R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda,
Macromolecules, 2005, 38, 5359–5362; (b) L. D. M. Simenon,
M. M. J. Brown, A. R. Einerhand and R. E. F. De, Synth.
Met., 1997, 87, 53–59.
O. Kitao, H. Nakai, T. Vreven, J. A. Montgomery Jr, 32 (a) J. S. Wu, J. F. Jheng, J. Y. Chang, Y. Y. Lai, K. Y. Wu,
J. E. Peralta, F. Ogliaro, M. Bearpark, J. J. Heyd,
E. Brothers, K. N. Kudin, V. N. Staroverov, R. Kobayashi,
J. Normand, K. Raghavachari, A. Rendell, J. C. Burant,
S. S. Iyengar, J. Tomasi, M. Cossi, N. Rega, J. M. Millam,
M. Klene, J. E. Knox, J. B. Cross, V. Bakken, C. Adamo,
J. Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev,
C. L. Wang and C. S. Hsu, Polym. Chem., 2014, 5, 6472–
6479; (b) J. F. Jheng, Y. Y. Lai, J. S. Wu, Y. H. Chao,
C. L. Wang and C. S. Hsu, Adv. Mater., 2013, 25, 2445–
2451; (c) C. J. Takacs, Y. Sun, G. C. Welch, L. A. Perez,
X. Liu, W. Wen and A. J. Heeger, J. Am. Chem. Soc., 2012,
134, 16597–16606.
A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, 33 (a) S. Zhang, L. Ye, W. Zhao, D. Liu, H. Yao and J. Hou,
R. L. Martin, K. Morokuma, V. G. Zakrzewski, G. A. Voth,
P. Salvador, J. J. Dannenberg, S. Dapprich, A. D. Daniels,
O. Farkas, J. B. Foresman, J. V. Ortiz, J. Cioslowski and
D. J. Fox, Gaussian 09, Revision A.1, Gaussian Inc.,
Wallingford CT, 2009.
Macromolecules, 2014, 47, 4653–4659; (b) C. W. Ge,
C. Y. Mei, J. Ling, F. G. Zhao, H. J. Li, L. Liang and
W. S. Li, J. Polym. Sci., Part A: Polym. Chem., 2014, 52,
2356–2366.
This journal is © The Royal Society of Chemistry 2015
RSC Adv., 2015, 5, 30445–30455 | 30455