Preparation and characterization of solution processable phthalocyanine-containing polymers via a combination of RAFT polymerization and post-polymerization modification techniques

Article abstract of DOI:10.1002/pola.27051

In this work, a benzenedinitrile functionalized monomer, 2-methyl-acrylic acid 6-(3,4-dicyano-phenoxy)-hexyl ester, was successfully polymerized via the reversible addition-fragmentation chain transfer method. The polymerization behavior conveyed the characteristics of living /controlled radical polymerization: the first-order kinetics, linear increase of number-average molecular weight with monomer conversion, narrow molecular weight distribution, and successful chain-extension experiment. The soluble Zn(II) phthalocyanine (Pc)-containing (ZnPc) polymers were achieved by post-polymerization modification of the obtained polymers. The Zn(II) phthalocyanine-functionalized polymer was characterized by FTIR, UV-vis, fluorescence, atomic absorption spectroscopy, and thermogravimetric analysis. The potential application of above ZnPc-functionalized polymer as electron donor material in bulk heterojunction organic solar cell was studied. The device with ITO/PEDOT:PSS/ZnPc-Polymer/ PC₆₁BM/LiF/Al structure provided a power conversion efficiency of 0.014%, fill factor of 0.24, open circuit voltage (V_oc) of 0.21 V, and short-circuit current (J_sc) of 0.28 mA/cm². Copyright

Full text of DOI:10.1002/pola.27051

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Preparation and Characterization of Solution Processable Phthalocyanine-
Containing Polymers via a Combination of RAFT Polymerization and Post-
Polymerization Modification Techniques
Jian Zhang, Laibing Wang, Chao Li, Yaowen Li, Jiangfei Liu, Yingfeng Tu, Wei Zhang,
Nianchen Zhou, Xiulin Zhu
Jiangsu Key Laboratory of Advanced Functional Polymer Design and Application, Department of Polymer
Science and Engineering, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou
215123, People’s Republic of China
Correspondence to: W. Zhang (E-mail: weizhang@suda.edu.cn) or X. Zhu (E-mail: xlzhu@suda.edu.cn)
Received 22 July 2013; accepted 29 November 2013; published online 17 December 2013
DOI: 10.1002/pola.27051
ABSTRACT: In this work,
a
benzenedinitrile functionalized
and thermogravimetric analysis. The potential application of
above ZnPc-functionalized polymer as electron donor material
in bulk heterojunction organic solar cell was studied. The
device with ITO/PEDOT:PSS/ZnPc-Polymer/PC61BM/LiF/Al struc-
ture provided a power conversion efficiency of 0.014%, fill
factor of 0.24, open circuit voltage (Voc) of 0.21 V, and short-
monomer, 2-methyl-acrylic acid 6-(3,4-dicyano-phenoxy)-hexyl
ester, was successfully polymerized via the reversible addition-
fragmentation chain transfer method. The polymerization
behavior conveyed the characteristics of “living”/controlled
radical polymerization: the first-order kinetics, linear increase
of number-average molecular weight with monomer conver-
sion, narrow molecular weight distribution, and successful
chain-extension experiment. The soluble Zn(II) phthalocyanine
(Pc)-containing (ZnPc) polymers were achieved by post-
polymerization modification of the obtained polymers. The
Zn(II) phthalocyanine-functionalized polymer was characterized
by FTIR, UV–vis, fluorescence, atomic absorption spectroscopy,
circuit current (Jsc) of 0.28 mA/cm2.
2013 Wiley Periodicals,
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Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 691–698
KEYWORDS: functionalization of polymers; living polymeriza-
tion; phthalocyanine; addition-fragmentation chain transfer
(RAFT); solar cell
tramerization reactions of bifunctional monomers. The side-
chain polymeric Pcs/MtPcs were mainly prepared via poly-
merization of Pc/MtPc-containing monomers or “grafting to”
reactions. However, the synthesis of Pc/MtPc containing
monomers or asymmetric Pcs is relatively difficult due to the
relatively low yield.
INTRODUCTION Phthalocyanines (Pcs) and metallophthalo-
cyanines (MtPcs) have recently received considerable atten-
tion due to their unique properties, such as high thermal
and chemical stability, excellent photoconductivity, intense
optical absorptions in visible–near infrared optical region,
and the well-defined coupling of the electronic p-systems.1–5
Because of these special properties, Pcs and MtPcs have
been widely studied as photosensitizer in solar energy con-
version,6–8 photodynamic therapy,9,10 catalysts,11–13 informa-
tion storage,14,15 optically active self-assembly, and so
on.16,17 However, the poor solubility and slippery p–p stacks
limited their applications. To overcome these drawbacks, sev-
eral approaches were explored.18–20 Among them, polymeric
Pcs/MtPcs have been paid much attention recently, which
offers a unique combination of good properties of polymers
and Pcs/MtPcs. Two kinds of polymeric Pcs/MtPcs, main-
chain and side-chain types, have been reported.21–23 The
main-chain polymeric Pcs/MtPcs were mainly synthesized by
the coordination of bidentate ligands with MtPcs and cyclote-
With the development of “living”/controlled radical polymer-
ization (LRP) techniques, such as atom transfer radical poly-
merization
(ATRP),24,25
nitroxide-mediated
radical
polymerization (NMRP),26 reversible addition-fragmentation
chain transfer (RAFT),27–29 reversible chain transfer cata-
lyzed polymerization (RTCP),30 and single-electron-transfer
mediated living radical polymerization (SET-LRP),31 a wide
variety of polymers with precise control over molecular
weights, compositions, and architectures are possible to be
synthesized. As one of the most promising LRP techniques,
RAFT method has been successfully used to prepare the
polymers with various functional groups due to its higher
Jian Zhang and Laibing Wang contributed equally to this work
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tolerance to many functional groups like allyl, amino, epoxy,
hydroxyl, and vinyl groups present in the monomers.32–35
Post-polymerization modification, also known as polymer-
analogous modification, is the other attractive approach for
preparation of functional polymers, allowing incorporation of
functionality incompatible with the polymerization and
greatly facilitates the establishment of structure-property
relationships.36,37 Up to now, several chemical reactions,
such as Michael-type addition, radical thiol addition,
thiol exchange, Huisgen 1,3-Dipolar cycloaddition reactions,
and so on, have been successfully used to prepare
functional polymers via post-polymerization modification
technique.38–41
photometer. FTIR spectra were recorded on a Nicolette-6700
FTIR spectrometer. The fluorescence spectra of polymers in
THF solution were recorded by HITACHI F-2500 fluorescence
spectrophotometer. Atomic absorption spectrometry was
detected by Varian Spectra 220FS atomic absorption spec-
trometer. Thermogravimetric analysis (TGA) was performed
with the PerkinElmer instruments (TGA 7) analyzer well
equipped with a PC at a heating rate of 10 ꢀC/min under
nitrogen atmosphere (20 cm3/min) and in the temperature
range of 30–900 ꢀC. Current–voltage characteristics of the
solar cells in the dark and under illumination of 100 mW/
cm2 white light from a Hg–Xe lamp filtered by a Newport
81094 Air Mass Filter, using a GWinstek SFG-1023 source
meter. Monochromatic light from Hg–Xe lamp (Newport
67005) in combination with monochromator (Oriel, Corner-
stone 260) was modulated with a mechanical chopper. The
response was recorded as the voltage over a 50 X resistance,
using a lock-in amplifier (Newport 70104 Merlin). A cali-
brated Si cell was used as reference. All the measurements
were performed under ambient atmosphere at room
temperature.
In this work, we reported the synthesis of the well-defined
side-chain benzenedinitrile-containing polymers via RAFT
technique. The post-polymerization modification of the above
polymer precursors, by reaction between benzenedinitrile
groups in the polymer chain and the added excess benzene-
dinitrile derivatives, produced Zn(II) phthalocyanine-
functionalized polymer. The potential application of above
ZnPc-functionalized polymer as electron donor material in
Bulk Heterojunction (BHJ) organic solar cell (OSC) was also
investigated.
Synthesis of 4-(6-Hydroxyhexyloxy) Phthalonitrile
The typical synthetic procedures of 4-(6-hydroxyhexyloxy)
phthalonitrile (HHPN) are as following: potassium carbonate
(0.36 g, 2.6 mmol) and 3,4-dicyanophenol (0.29 g, 2.0 mmol)
were dissolved in dry DMF (15 mL). The mixture was stirred
EXPERIMENTAL
Materials
ꢀ
at 80 C for 3 h. Then 6-bromo-1-hexanol (0.29 g, 1.6 mmol)
6-Bromo-1-hexanol (99%, J&K Chemical), 1,8-diazabicy-
clo[5.4.0]undec-7-ene (DBU) (99%, J&K Chemical), 1-
bromooctane (99%, J&K Chemical), and 3,4-dicyanophenol
(99%, J&K Chemical) were used as received. Azobisisobutyr-
onitrile (AIBN, 99%, J&K Chemical) was recrystallized twice
from ethanol before use. 2-Cyanoprop-2-yl 1-dithionaphtha-
late (CPDN) was synthesized according to the reference.42
Unless otherwise specified, all other chemicals were pur-
chased from Shanghai Chemical Reagents and used as
received without any further purification.
and a small amount of potassium iodide were added into
above mixture. The resulting mixture was refluxed for 12 h,
and then was allowed to cool slowly to room temperature.
Then ethyl acetate (100 mL) was added. The mixture was
washed with deionized water (3 3 100 mL). After being
dried over anhydrous MgSO4 overnight, ethyl acetate was
evaporated under reduced pressure and crude product was
purified by column chromatography (silica gel, ethyl acetate/
petroleum ether 5 1/8, v/v) to yield a white solid (0.33 g,
60%). Anal. calcd. for C14H16N2O2: C, 68.83%; H, 6.60%; N,
11.47%. Found: C, 68.55%; H, 6.82%; N, 11.52%.
Characterizations
1H NMR (400 MHz, DMSO-d6, d): 7.99–8.05 (d, 1H, phenyl),
7.70–7.78 (s, 1H, phenyl), 7.40–7.46 (d, 1H, phenyl), 4.32–
4.38 (s, 1H, OH), 4.08–4.16 (t, 2H, OCH2), 3.35–3.42 (t, 2H,
CH2OH), 1.65–1.78 (t, 2H, CH2), 1.28–1.48 (m, 4H, CH2CH2).
13C NMR (100 MHz, CDCl3, d): 162.48, 135.49, 119.93,
119.61, 117.30, 116.08, 115.60, 69.43, 62.65, 32.66, 28.87,
25.81, 25.61.
The number-average molecular weight (Mn) and molecular
weight distribution (Mw/Mn) of the polymer were deter-
mined using a Waters 1515 gel permeation chromatograph
(GPC) equipped with a refractive-index detector (Waters
2412), using HR1 (pore size: 100 Å, 100–5000 Da), HR2
(pore size: 500 Å, 500–20,000 Da), and HR4 (pore size
10,000 Å, 50–100,000 Da) columns (7.8 3 300 mm2, 5 lm
beads size) with molecular weights ranging from 102 to 5 3
105 g/mol. THF was used as the eluent at a flow rate of 1.0
Synthesis of 2-Methyl-acrylic Acid
6-(3,4-Dicyano-phenoxy)-hexyl Ester
ꢀ
mL/min at 40 C. GPC samples were injected using a Waters
717 plus auto sampler and calibrated with poly(methyl
Into THF (10 mL) solution of HHPN (0.24 g, 1.00 mmol) and
triethylamine (1.0 mL) under ice-bath condition, methacry-
loyl chloride (1.05 g, 1.00 mmol) in 10 mL THF was added.
The solution was stirred overnight at room temperature and
ethyl acetate (100 mL) was added to above solution. After
washing with water three times, the mixture was dried with
anhydrous MgSO4 overnight. Then ethyl acetate was evapo-
rated under reduced pressure and crude product was
1
methacrylate) standards. H NMR and 13C NMR spectra were
recorded on an INOVA 400 MHz nuclear magnetic resonance
(NMR) instrument using CDCl3 or DMSO-d6 as the solvent
and tetramethylsilane (TMS) as the internal standard at
ambient temperature. Elemental analysis of C, H, and N was
measured with an EA1110 CHNO-S instrument. The UV–vis
spectra were recorded with a Shimadzu UV-3100 spectro-
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purified by column chromatography (silica gel, ethyl acetate/
petroleum ether 5 1/10, v/v) to yield a white solid (1.10 g,
85%). Anal. calcd. for C18H20N2O3: C, 69.21%; H, 6.45%; N,
8.97%. Found: C, 69.07%; H, 6.20%; N, 8.79%.
tatingꢀtwice from THF to methanol and dried under vacuum
at 30 C until a constant weight.
Synthesis of 4-(Octyloxy) Phthalonitrile
4-(Octyloxy) phthalonitrile (OPN) was prepared with the
similar procedure to that of HHPN. The product was recrys-
tallized from methanol to yield a white solid (0.42 g, 78%).
Anal. calcd. for C16H20N2O: C, 74.97%; H, 7.86%; N, 10.93%.
Found: C, 74.82%; H, 7.92%; N, 11.02%.
1H NMR (400 MHz, CDCl3, d): 7.65–7.76 (d, 1H, phenyl),
7.22–7.30 (s, 1H, phenyl), 7.12–7.21 (d, 1H, phenyl), 6.05–
6.15 (s, 1H, C@CH2), 5.52–5.60 (s, 1H, C@CH2), 4.11–4.22 (t,
2H, OCH2), 3.99–4.10 (t, 2H, OCH2), 1.91–1.98 (s, 3H, CH3),
1.79–1.90 (m, 2H, CH2), 1.65–1.78 (m, 2H, CH2), 1.40–1.58
(m, 2H, CH2). 13C NMR (100 MHz, CDCl3, d): 167.69, 162.43,
136.65, 135.47, 125.54, 119.84, 119.59, 117.54, 116.04,
115.59, 107.15, 69.38, 64.70, 28.87, 28.70, 25.89, 25.74,
18.56.
1H NMR (400 MHz, DMSO-d6, d): 8.02–8.07 (d, 1H, phenyl),
7.74–7.77 (s, 1H, phenyl), 7.41–7.46 (d, 1H, phenyl), 4.08–
4.17 (t, 2H, OCH2), 4.11–4.22 (t, 2H,), 3.99–4.10 (t, 2H,
OCH2), 1.68–1.77 (m, 2H, CH2), 1.34–1.43 (m, 2H, CH2),
1.20–1.32 (m, 6H, CH2CH2CH2CH2), 0.83–0.88 (t, 3H, CH3).
13C NMR (100 MHz, CDCl3, d): 162.49, 135.43, 119.84,
119.55, 117.47, 116.05, 115.59, 106.99, 69.57, 31.95, 29.39,
28.93, 26.00, 22.83.
General Procedures for RAFT Polymerization of 2-
Methyl-acrylic Acid 6-(3,4-Dicyano-phenoxy)-hexyl Ester
2-Methyl-acrylic acid 6-(3,4-dicyano-phenoxy)-hexyl ester
(MADCE) (0.5 g, 1.6 mmol), AIBN (0.60 mg, 0.032 mmol),
and CPDN (1.74 mg, 0.064 mmol) were dissolved in 1 mL
DMF in a 5 mL dried ampoule. The ampoule was bubbled
with argon for 20 min to remove the dissolved oxygen from
the solution. Then the ampoule was flame-sealed and placed
in an oil bath held by a thermostat at the desired tempera-
ture (70 ꢀC). At the desired reaction time, the ampoule was
cooled by immersing it into cold water. Then the ampoule
was opened and the contents were dissolved in 10 mL of
THF, and precipitated into 400 mL of methanol. The polymer
(PMADCE) was obtained by filtration and dried under vac-
Synthesis of Polymeric Zn(II) Phthalocyanine
(PMADCE–ZnPc)
PMADCE (0.09 g, Mn(GPC) 5 9500 g/mol, Mw/Mn 5 1.10), OPN
(0.75 g, 2.93 mmol), and zinc acetate dihydrate (0.1 g, 0.45
mmol) were mixed in 15 mL of dry N,N-dimethylacetamide
(DMAC) and heated at 80 ꢀC. After adding a few drops of
1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), the temperature
ꢀ
ꢀ
was raised to 130 C. The mixture was kept at 130 C over-
night. The contents were dissolved in 10 mL of THF, and
then precipitated into 500 mL of methanol. The polymeric
phthalocyanine (PMADCE–ZnPc) was obtained by filtration.
The crude product was extracted in a Soxhlet Extractor with
ether. The final product was dried under vacuum at 30 ꢀC
until a constant weight to afford a dark green solid.
ꢀ
uum at 30 C until a constant weight. The monomer conver-
sion was determined gravimetrically.
Chain Extension of PMADCE Using PMADCE as
a Macro-CTA
The PMADCE sample prepared by RAFT polymerization
(Mn(GPC) 5 9500 g/mol, Mw/Mn 5 1.10) was used as a macro-
CTA for the chain extension reaction with MADCE. PMADCE
(0.23 g, 0.026 mmol), AIBN (2.05 mg, 0.013 mmol), and
MADCE (0.2 g, 0.64 mmol) were dissolved in 1 mL of DMF
in a 5 mL dried ampoule. The following procedures were
similar to those described above, except that the CPDN was
replaced by PMADCE. The monomer conversion was deter-
mined gravimetrically. The Mn and Mw/Mn values
(Mn(GPC) 5 15,100 g/mol, Mw/Mn 5 1.15) were determined by
GPC with PMMA standards.
Device Fabrication
The active layer contained a blend of PMADCE–ZnPc as elec-
tron donor and PC61BM as electron acceptor was prepared
from weight ratios (1:1, w/w) by solution (15 mg/mL of
PMADCE–ZnPc) in chlorobenzene. After spin coating the
blend from solution at 1000–1400 rpm, the device was com-
pleted by evaporating a 0.8 nm LiF layer protected by 100
nm of Al at a base pressure of 4 3 1024 Pa. The effective
photovoltaic area defined by the geometrical overlap
between the bottom ITO electrode and the top cathode was
12 mm2.
The Pretreatment of PMADCE
RESULTS AND DISCUSSION
To eliminate the possible effect of the thiocarbonylthio
groups on the next post-polymerization modification reac-
tion, thiocarbonylthio groups at the ends of PMADCE chains
were removed using the procedure previously reported by
Perrier et al.43 The obtained PMADCE was treated with a
large amount of AIBN. PMADCE (0.1 mmol) and AIBN (1.5
mmol) (10 times more than the amounts of PMADCE) were
dissolved in dry THF (20 mL). The mixture was stirred at 70
ꢀC for 12 h under nitrogen atmosphere. Then the reaction
solution was precipitated into large amounts of methanol. A
white powder was isolated by filtration along with a pink fil-
trate. Then the processed PMDCHE was purified by precipi-
RAFT Polymerization of MADCE
The synthetic pathways of monomer (MADCE) and corre-
sponding polymer (PMADCE) are presented in Scheme 1.
RAFT polymerization of MADCE was performed with a feed
ratio of [MADCE]0:[AIBN]0:[CPDN]0 5 50:1:2, using CPDN as
the RAFT agent and AIBN as the initiator at 70 ꢀC in DMF
(MADCE/DMF 5 0.5 g/1.0 mL). The results are shown in Fig-
ures 1 and 2. The first-order kinetics was observed in Figure
1, demonstrating the propagating radical concentrations kept
constant during the polymerization process. The linear
increase of number-average molecular weight (Mn(GPC)) with
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SCHEME 1 The synthetic routes of the MADCE and polymeric Zn(II) phthalocyanine.
monomer conversion with the narrow molecular weight dis-
tribution (Mw/Mn < 1.15) was found in Figure 2. Further-
more, the Mn(GPC) values of the obtained polymers are very
close to their corresponding theoretical ones as presented in
Figure 2. The theoretical molecular weight of the polymer
was calculated from the following equation:
results indicated that the polymerization of MADCE can be
well-controlled via a RAFT process.
Analysis of Chain End of Polymer and Chain-Extension
Experiment
The chain end of the PMADCE prepared via RAFT polymer-
ization was characterized by 1H NMR spectrum as given in
Figure 3. The characteristic signals corresponding to the phe-
nyl protons of the benzenedinitrile group were observed
from 7.20 to 8.10 ppm (a, b, c). The signals at 4.0 ppm (d, e)
are assigned to the methylene group of ACH2AOA in
the side chain. The peak at around d 5 8.10–8.20 (f)
(I8.10–8.20 5 1.00) is ascribed to the 8-position proton of the
½MADCEꢁ
½CPDNꢁ0
MnðthÞ
5
0 3MMADCE 3Conversion1MCPDN
;
where [MADCE]0 and [CPDN]0 are the initial concentrations
of the MADCE and the RAFT agent, MMADCE and MCPDN are
the molar mass of the monomer and CPDN. All the above
FIGURE 2 Dependence of the molecular weights and the
molecular weight distributions on the monomer conversions
for the RAFT polymerization of MADCE. The polymerization
conditions are the same as in Figure 1.
FIGURE 1 Ln([M]0/[M]) versus polymerization time for RAFT
polymerization of MADCE. Polymerization conditions: [MADCE]0/
[CPDN]0/[AIBN]0 5 50/2/1, T 5 70 ꢀC, MADCE/DMF 5 0.5 g/mL.
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(Mn(GPC 5 9500 g/mol), indicating that PMADCE was end-
capped by CPDN species with high fidelity.
The living feature of the obtained polymer was further verified
by a chain-extension experiment. As presented in Figure 4, an
apparent peak shift from the macro-CTA with Mn(GPC) 5 9500
g/mol and Mw/Mn 5 1.10 to the chain extended PMADCE with
Mn(GPC) 5 15,100 g/mol and Mw/Mn 5 1.15 was found, respec-
tively. The presence of species of RAFT agent in the polymer
chain and the successful chain extension experiment both
proved the functionality of the obtained polymer and feature
of the “living”/controlled polymerization of MADCE.
Preparation of Polymeric Zn(II) Phthalocyanine
PMADCE–ZnPc Via Post-polymerization Modification
Technique
Post-polymerization modification technique is a powerful tool
for the preparation of functional polymers, which can avoid
the limited functional-group to tolerance of polymerization
methods and difficulty existed in synthesizing corresponding
monomers.21–23 The polymeric Pcs/MtPcs can improve the
solubility and processability of Pc materials.36,37 However, the
synthesis of asymmetric Pc derivatives is relatively difficult
with relatively low yields, which limited the preparation of
side chain Pc-containing polymers. Here, we described the
preparation of side chain Pc-containing polymers via post-
polymerization modification technique. PMADCE–ZnPc was
synthesized via chemical reaction between benzenedinitrile
groups in PMADCE and those in added reagent (M in Scheme
1). The obtained PMADCE–ZnPc was analyzed by UV–vis, fluo-
rescence, FTIR, and TGA as shown in Figures 5–8.
FIGURE 3 1H NMR spectrum of the PMADCE (Mn(GPC) 5 9500 g/
mol, Mw/Mn 5 1.10) with DMSO-d6 as the solvent and TMS as
the internal standard.
naphthalene unit in CPDN units, revealing that the
dithioester units were successfully attached to the polymer
chain ends (x-chain end). The peak at around d 5 7.25–7.41
(c) (I7.25–7.41 5 30.19) corresponds to the aromatic proton of
the benzene unit in MADCE repeat units. Assuming that each
polymer chain was captured by a naphthyl moiety from
CPDN, the molecular weight (Mn(NMR)) of PMAECD can be
1
calculated from the corresponding integrals in H NMR spec-
trum, according to the following equation:
312:36
Photophysical Properties
UV–Vis Absorption and Fluorescence Spectra
MnðNMRÞ ðg=molÞ 5 ðI7:2527:41
Þ
1 271:5;
ðI8:1028:20
Þ
Phthalocyanines consisting of four isoindole units presenting
an 18p-electron heterocyclic aromatic system, their intrinsic
absorption spectra indicate intense Q-bands in the visible–
near infrared optical region, approximately from 600 to 700
nm.44,45 Figure 5 shows the typical UV–vis spectra of the
polymer precursor (PMADCE) and the Zn(II) phthalocyanine-
where 312.36 and 271.5 are the molecular weights of MADCE
and CPDN, respectively. The molecular weight of PMADCE
calculated from H NMR spectrum was 9700 g/mol, which is
1
consistent with that from normal GPC measurement
FIGURE 4 GPC curves of PMADCE before and after chain
extension. Polymerization conditions: [MADCE]0/[PMADCE]0/
[AIBN]0 5 50/2/1, T 5 70 ꢀC, t 5 6 h, MADCE/DMF 5 0.5 g/mL.
FIGURE 5 UV–vis spectra of (a) PMADCE and (b) PMADCE–
ZnPc in THF solution (Cn 5 1.1 3 1025 mol/L ZnPc mesogens).
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FIGURE 6 Fluorescence spectra of (a) PMADCE and (b)
PMADCE–ZnPc in THF solution (Cn 5 1.1 3 1026 mol/L ZnPc
mesogens), kex 5 380 nm.
FIGURE 7 FTIR spectra of (a) PMADCE and (b) PMADCE–ZnPc.
functionalized polymer (PMADCE–ZnPc) in THF. As pre-
sented in Figure 5, the intense p–p bands in the visible
(from 660 to 690 nm, kmax 5 682 nm) and UV (from 330 to
360 nm, kmax 5 350 nm) spectral regions ascribed to the typ-
ical Q-band and B-band of Pc ring were observed after post-
polymerization modification. The fluorescence spectra of
PMADCE and PMADCE–ZnPc in THF are shown in Figure 6.
As compared with the fluorescence spectrum of PMADCE,
PMADCE–ZnPc showed the strong emission with a major
peak between 670 and 700 nm with an excitation wave-
length of 380 nm. As discussed above, we have prepared the
polymeric phthalocyanine (PMADCE–ZnPc) successfully.
heated to 850 ꢀC for 12 h with a constant oxygen gas flow.
After being cooling naturally, the white powder was found
on the combustion boat. The ashed sample was dissolved in
dilute hydrochloric acid (0.05 mol/L, 100 mL). Zinc content
was analyzed by atomic absorption spectroscopy to be 1.05
mg/L, and the zinc content in the PMADCE–ZnPc was calcu-
lated to be 3.6%. Based on the above result, about 64%
molar ratio of cyano groups in PMADCE took part in the
chemical reaction with 4-(octyloxy) phthalonitrile in the
presence of zinc acetate dihydrate, which resulted in cova-
lently bound Zn(II) phthalocyanine-functionalized polymer
(PMADCE–ZnPc) with a loading about 32% of Pc ring.
Infrared Spectra
Photoelectric Property
Further confirmation of the phthalocyanine-forming reaction
can be taken from IR spectra. Figure 7 shows the IR spectra
of the PMADCE (a) and PMADCE–ZnPc (b). The strong signal
at 2230 cm21 assigned to the cyano groups existed in
PMADCE almost disappeared after post-polymerization modi-
fication reaction, which proved the reaction leading to
the covalently bound polymeric phthalocyanine while the
absorptions at 2940 and 1725 cm21 remain. Moreover, the
typical absorptions of Pc ring in PAMDCE-ZnPc at 1330,
1090, 750, and 460 cm21 were observed, respectively.46
Pcs/MtPcs have been widely investigated in BHJ OSC due to
their excellent stability, low bandgap, high hole mobility, and
so on.47–49 Recently, many studies on the phthalocyanine/
fullerene solar cells have been reported.50,51 To investigate
the photovoltaic property of the PMADCE–ZnPc, the bulk het-
erojunction photovoltaic cell, with
PEDOT–PSS/PMADCE–ZnPc:PC61BM/LiF/Al was fabricated,
where the PMADCE–ZnPc was used as donor and PC61BM as
a structure of ITO/
Thermal Properties
Thermal stabilities of the polymers (PMADCE and PMADCE–
ZnPc) were investigated with thermogravimetric analysis
(TGA) under N2 at a heating rate of 10 ꢀC/min and the
results are shown in Figure 8. The TGA analysis showed that
the onset decomposition temperatures with 5% weꢀight loss
ꢀ
of PMADCE and PMADCE–ZnPc are 295 C and 349 C in N2,
respectively. This indicates that the PMADCE–ZnPc had bet-
ter thermostability compared to that of PMADCE.
Atomic Absorption Spectroscopy
Atomic absorption spectroscopy was also used to study the
zinc content of the functionalized polymer PMACDE–ZnPc.
The sample PMACDE–ZnPc (2.9 mg) was placed on the com-
bustion boat in a horizontal quartz tube furnace, and then
FIGURE 8 TGA curves of (a) PMADCE and (b) PMADCE–ZnPc.
696
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reversible addition-fragmentation chain transfer (RAFT) poly-
merization and post-polymerization modification technique.
The polymerization of MADCE was a “living”/controlled proce-
dure and the phthalocyanine-forming reaction was performed
under mild reaction conditions. Reaction of dinitrile groups in
PMADCE with 4-(octyloxy) phthalonitrile in the presence of
zinc acetate dihydrate results in the formation of covalently
bound Zn(II) phthalocyanine-functionalized polymer. The
Zn(II) phthalocyanine-functionalized polymer has good solu-
bility in THF or chlorobenzene and shows good thermal sta-
bility. The Zn(II) phthalocyanine-functionalized polymer has
potential application as electron donor material in solar cell.
ACKNOWLEDGMENTS
The financial support from the Project of International Cooper-
ation of the Ministry of Science and Technology of China
(2011DFA50530), the Suzhou Project of Applied and Funda-
mental Research (SYG201111), the National Nature Science
Foundation of China (21104052 and 21004042), the Qing Lan
Project, the Program of Innovative Research Team of Soochow
University, and the Project Funded by the Priority Academic
Program Development of Jiangsu Higher Education Institutions
(PAPD) are gratefully acknowledged.
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