Synthesis and photoluminescent property of star polymers with carbzole pendent and a zinc porphyrin core by ATRP

Article abstract of DOI:10.1016/j.polymer.2011.07.025

Styrene-type monomer 9-(4-vinylbenzyl)-9H-carbazole (VBCz) and methacrylate-type monomer 2-(9Hcarbazole- 9-yl)-ethyl methacrylate (CzEMA) were polymerized to star polymers respectively via atom transfer radical polymerization (ATRP) using zinc 5,10,15,20-

Full text of DOI:10.1016/j.polymer.2011.07.025

Polymer 52 (2011) 4261e4267
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Polymer
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Synthesis and photoluminescent property of star polymers with carbzole pendent
and a zinc porphyrin core by ATRP
,
,
a
a
Yongxin Tao a b, Qingfeng Xu a, Najun Li a, Jianmei Lu a , Lihua Wang , Xuewei Xia
*
a Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, Jiangsu 215123, PR China
b Key Laboratory of Fine Chemical Engineering of Jiangsu Province, Changzhou University, Changzhou, Jiangsu 213164, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Styrene-type monomer 9-(4-vinylbenzyl)-9H-carbazole (VBCz) and methacrylate-type monomer 2-(9H-
carbazole-9-yl)-ethyl methacrylate (CzEMA) were polymerized to star polymers respectively via atom
transfer radical polymerization (ATRP) using zinc 5,10,15,20-tetrakis(4-(2-methyl-2-bromopropoxy)
phenyl) porphyrin as an initiator. The emission spectra of two star polymers (star poly(VBCz) and star
poly(CzEMA)) in the solid state displayed red light emission, while those of two monomers showed blue
light emission. The result demonstrates that effective energy transfer occurs from the carbazole to the Zn
porphyrin core. However, two star polymers in DMF solution emit week red light and strong UV light
at 350e400 nm, it points that energy transfer cannot occur from the carbazole to the Zn porphyrin
Received 15 March 2011
Received in revised form
1 July 2011
Accepted 19 July 2011
Available online 30 July 2011
Keywords:
Atom transfer radical polymerization (ATRP)
Star polymer
Porphyrin
core effectively. They exhibit good thermal stability with Td poly(VBCz) ¼ 374 ꢀC and Td poly(CzEMA) ¼ 297 ꢀ
C
at 5% weight loss. The DSC curves show that the glass transition temperature of styrene-type
(Tg poly(VBCz) ¼ 177 ꢀC) was better than that of methacrylate-type (Tg poly(CzEMA) ¼ 148 ꢀC).
Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction
architecture, narrow molecular weight distribution, and high
chain-end functionality that allows further chemical modifications
Much attention has been paid to star-shaped derivatives and
dendrimers from porphyrin and metal porphyrin owing to their
special chemical and physical features relevant in various fields
such as red light-emitting dyes [1e7], light harvesting materials [8],
hemoprotein mimic and dioxygen binding [9,10], photodynamic
therapy [11], and oxidation catalysis [12]. A variety of dendrimers
built from porphyrin subunits have been reported [13e20]. Their
regularly layered and symmetrically branched three-dimensional
architecture and accurately controlled placement of functional-
ities made them useful in either photochemically, electrochemi-
cally, or catalytically active [16,20]. As its analogs, star polymers
have recently received particular attention due to less synthetic
steps and many end group functionalities within a single molecule,
which are helpful for various applications. The synthesis of star
polymers from porphyrin has been successful by polymerization of
an epoxide system [21,22], ring opening polymerization [23e28],
Suzuki polycondensation [29] and controlled radical polymeriza-
tion (CRP) [30,31]. Atom transfer radical polymerization (ATRP),
one of the most powerful CRP techniques [32e34], has been
successfully used to prepare star polymers with a controlled
via one of three strategies: (i) “core-first” (ii) “arm-first” and (iii)
“coupling onto” [35e37]. In the “core-first” strategy, a multifunc-
tional initiator is used to initiate the monomers to obtain multiarm
star polymers. Holder et al. first reported that well-defined four-
arm star polymer of styrene and alkyl (meth)acrylates could be
synthesized from tetrabromo porphyrin-based initiators via ATRP
and the coordination of zinc ion and porphyrin initiator could avoid
copper ion as catalyst into porphyrin in star polymers [31].
In addition, it is well-known that carbazole is electron-donor
group and attaching a carbazole moiety to the molecular scaffold
can significantly enhance the thermal stability and HOMO energy
level of light-emitting polymers [38]. The doping of fluorescent red
dye tetraphenylporphyrin into the blue light-emitting polymer can
provides efficient transfer of energy from blue to red [39]. For
efficient Förster energy transfer to the dopant, the spectral overlap
between the photoluminescence band of the host material and the
absorption band of the dopant is indispensable [40]. However, the
emission peak of chromophore in solid state compared to in dilute
solution may appear red-shifted in a certain degree [41].
To the best of our knowledge, only a few literatures have been
found on the properties and functions of the well-defined energy
donoreacceptor star polymers [2,24]. In the present work, we
report the synthesis of two red light-emitting star polymers
* Corresponding author.
E-mail address: lujm@suda.edu.cn (J. Lu).
0032-3861/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.polymer.2011.07.025

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Y. Tao et al. / Polymer 52 (2011) 4261e4267
together with their absorption spectra, fluorescent spectra and
thermal properties. Two star polymers were prepared using
zinc 5,10,15,20-tetrakis (4-(2-methyl-2-bromo-propoxy) phenyl)
porphyrin as initiator, 9-(4-vinylbenzyl)-9H-carbazole (styrene-
type) and 2-(9H-carbazole-9-yl)-ethyl methacrylate (methacrylate-
type) as monomer, respectively, via ATRP. To better understand the
fluorescent properties of two star polymers and the energy transfer
from carbazole to zinc porphyrin, the fluorescent spectra of star
polymers and the monomers both in solid state and in solution
were investigated.
with methanol and dried in vacuum. Characteristics were as
follows: Purple powder yield 95%. 1H NMR (CDCl3, 500 MHz):
d
(ppm) 2.24 (s, 24H, C(CH3)2Br), 7.56e7.58 (d, 8H, J ¼ 8.5Hz, AreH),
8.24e8.26 (d, 8H, J ¼ 8.5Hz, AreH), 8.98 (s, 8H, pyrroleeH). Anal.
Calcd for C60H50Br4N4O8Zn: C, 53.86; H, 3.62; N, 4.19. Found: C,
53.45; H, 3.59; N, 4.16. Absorption spectra data in CH2Cl2: 425, 554,
596 nm.
2.5. Synthesis of the monomers pendant carbazole [42]
2.5.1. Preparation of 9-(4-vinylbenzyl)-9H-carbazole (VBCz)
2. Experimental section
A mixture of carbazole (4.17 g, 25.0 mmol), potassium hydroxide
(2.10 g, 37.5 mmol), 4-vinyl benzyl chloride (4.18 g, 27.5 mmol) and
hexadecyl trimethyl ammonium bromide (40 mg, 0.11 mmol) in
THF 50 mL was stirred at 75 ꢀC for 24 h. After cooling to room
temperature, the mixture was poured into deionized water 500 mL
and the resultant white precipitate was filtered off and dried in
vacuum. The crude product was purified by recrystallization from
acetone to yield 4.45 g (62.9%) of white crystals. Parameters were:
2.1. Materials
4-Chloromethyl styrene was purchased from Sinopharm and
passed through a short column of alumina to remove inhibitors
prior to use, and was finally purified by distillation in vacuum.
Copper(I) bromide (CuBr) (CP, Sinopharm) was agitated in acetic
acid, filtered, washed with ethanol absolute, and dried in vacuum.
1,1,4,7,7-Pentamethyldiethylenetriamine, PMDETA (98%, Jiangsu
Liyang Jiangdian Chemical Factory) was dried with 4-Å molecular
sieve and distilled in vacuum. Cyclohexanone (AR, Sinopharm) was
dried with magnesium sulfate overnight and distilled in vacuum.
Other reagents were supplied as analytic pure and were used
without further purification.
1H NMR (CDCl3, 400 MHz):
d (ppm) 5.18e5.21 (d, 1H, vinyl), 5.51 (s,
2H, eCH2), 5.65e5.70 (d, 1H, vinyl), 6.59e6.69 (m, 1H, vinyl),
7.08e7.13 (d, 2H, AreH), 7.22e7.45 (m, 8H, AreH), 8.12e8.15 (d, 2H,
AreH). Anal. Calcd for C21H17N: C, 89.01; H, 6.05; N, 4.94. Found: C,
88.89; H, 5.87; N, 4.89.
2.5.2. Preparation of 2-(9H-carbazole-9-yl)-ethyl methacrylate
(CzEMA)
2.2. Instruments and methods
2.5.2.1. 2-(9H-Carbazole-9-yl) ethanol. A mixture of carbazole
(4.17 g, 25.0 mmol) and potassium hydroxide (2.10 g, 37.5 mmol) in
DMF 50 mL was stirred for 1 h and chloroethanol (2.95 g,
37.5 mmol) was added in drops. After stirring for 12 h at room
temperature, the mixture was poured into deionized water 500 mL
and the resultant white precipitate was filtered off. The reactant
was dissolved in aqueous alcohol (70%Vol) 20 mL and insoluble
matter was removed by filtering. The filtrate was poured into
deionized water 100 mL, and the white flocculent precipitate was
filtered off and dried in vacuum. Yield 4.01 g (75.4%).
1H NMR spectra were measured on INOVA 400 MHz NMR or
Bruker AV 500 MHz spectrometers at ambient temperature, using
CDCl3 as solvent. Element analyses were obtained with a Carlo
Erba-MOD1106 instrument. UVevis absorption spectra were
recorded with
a Shimadzu UV-3150 spectrometer. Monomer
conversion was determined by gravimetry, molecular weight and
the polydispersity relative to polystyrene was measured using
a Waters1515 GPC with THF as eluent and a column temperature of
30 ꢀC. Room temperature emission and excitation spectra were
recorded using an Edinburgh-920 fluorescence spectrophotometer.
The thermal gravimetric analysis (TGA, 2960 SDT V3.0F, TA
Instruments) and differential scanning calorimetry (DSC, 2010DSC
V4.4E, TA Instruments) measurements were carried out under
a nitrogen atmosphere at a heating rate of 20 ꢀC/min.
2.5.2.2. 2-(9H-Carbazole-9-yl)-ethyl
methacrylate. Methacryloyl
chloride (7.95 g, 40.0 mmol) was added dropwise into a solution of
2-(9H-carbazole-9-yl) ethanol (4.00 g, 19.0 mmol) in chloroform
50 mL and triethyl-amine (7.60 g, 75.0 mmol) at 0e5 ꢀC and reacted
for 12 h. The crude product was isolated by evaporating the solvent
and purified twice by recrystallization from 95% alcohol to yield
4.34 g (82.1%) of the white crystals. 1H NMR (CDCl3, 400 MHz):
2.3. Tetrafunctional porphyrin initiator
d
(ppm) 1.80 (s, 3H, eCH3), 4.52e4.55 (t, 2H, eCH2), 4.61e4.64 (m,
5,10,15,20-Tetrakis(4-(2-methyl-2-bromopropoxy) phenyl)-21H,
23H-porphine was prepared according to the literature recipe [31]
and the following parameters were obtained: Purple powder yield
90% from 5,10,15,20-tetrakis(4-hydroxyl phenyl)-21H, 23H-por-
2H, eCH2), 5.47e5.48 (m, 1H, vinyl), 5.93 (m, 1H, vinyl), 7.23e7.27
(m, 4H, AreH), 7.44e7.47 (m, 2H, AreH), 8.09e8.11 (m, 2H, AreH).
Anal. Calcd for C18H17NO2: C, 77.40; H, 6.13; N, 5.01. Found: C, 77.21;
H, 6.05; N, 4.99.
phine. 1H NMR (CDCl3, 500 MHz):
d
(ppm) ꢁ2.82 (s, 2H, NeH), 2.24
(s, 24H, C(CH3)2Br), 7.56e7.58 (d, 8H, J ¼ 8.0Hz, AreH), 8.24e8.26
(d, 8H, J ¼ 8.0Hz, AreH), 8.88 (s, 8H, pyrroleeH). Anal. Calcd for
C60H50Br4N4O8: C, 56.54; H, 3.95; N, 4.40. Found: C, 56.34; H, 3.89;
N, 4.38. Absorption spectra data in CH2Cl2: 419, 516, 549, 588,
646 nm.
2.6. ATRP procedures
Zinc porphyrin initiator (13.4 mg, 1.0 ꢂ 10ꢁ5 mol), CuBr (5.8 mg
4.0 ꢂ 10ꢁ5 mol), PMDETA (13.8 mg, 8.0 ꢂ 10ꢁ5 mol), VBCz (2.27 g,
8.0 ꢂ 10ꢁ3 mol), and cyclohexanone (9.1 g, 9.2 ꢂ 10ꢁ2 mol) were
mixed in a round-bottomed flask. The flask was sealed and cycled
between vacuum and N2 four times. The polymerization took place
in 90 ꢀC under N2 atmosphere. Samples were taken at regular
intervals for conversion and molecular weight analysis. The prod-
ucts were dissolved in THF and precipitated into a large amount of
methanol/HCl (100/0.5, v/v). The precipitate was filtered and dried
under vacuum. The crude polymers were purified by Soxhlet
extractor with ethanol to remove the starting monomers. Star
poly(CzEMA) was carried out similar experimental procedure.
2.4. Tetrafunctional Zn porphyrin initiator
Zinc 5,10,15,20-tetrakis(4-(2-methyl-2-bromopropoxy) phenyl)
porphyrin was synthesized by heating with 5,10,15,20-tetrakis(4-
(2-methyl-2-bromopropoxy)
phenyl)-21H,23H-porphine
and
ZnBr2 in dichloromethane/methanol under reflux conditions for
4 h. After cooling to room temperature, the mixture was poured
into methanol and the purple precipitate was filtered off, washed

Y. Tao et al. / Polymer 52 (2011) 4261e4267
4263
Polymerization condition: zinc porphyrin initiator (13.4 mg,
3.2. ATRP from tetrafunctional Zn porphyrin initiator
1.0 ꢂ 10ꢁ5 mol), CuBr (5.8 mg 4.0 ꢂ 10ꢁ5 mol), PMDETA (13.8 mg,
8.0
ꢂ
10ꢁ5 mol), CzEMA (2.23 g, 8.0
ꢂ
10ꢁ3 mol), and
Herein, ATRP was processed by using zinc 5,10,15,20-tetrakis (4-
(2-methyl- 2-bromopropoxy) phenyl) porphyrin as initiator, CuBr/
PMDETA as a catalyst system, and cyclohexanone as a solvent. We
selected proper ratio of polymerization is that: [monomer]/[initi-
ator]/[CuBr]/[PMDETA] ¼ 800:1:4:8, cyclohexanone ¼ 80 wt %.
VBCz polymerized at 90 ꢀC and CzEMA at 45 ꢀC is according to
typical ratio of ATRP of functional styrene-type and methacrylate-
type monomers in our previous work [43] and keep a relatively
low radical concentration. Gnanou has mentioned that the radical
concentration can be kept low by using high ratio of monomer to
initiator and stopping polymerization at lower conversions to
prevent starestar termination [44].
The kinetic plots of polymerization of VBCz are presented in
Fig. 1. The linearity of the semi-logarithmic plot of ln([M]0/[M]) vs
time indicates that the polymerization is first-order with respect to
the monomer and that the concentration of the growing radicals
remains constant. The number average molecular weights (Mn)
cyclohexanone(8.9 g, 9.2 ꢂ 10ꢁ2 mol), reaction temperature 45 ꢀC
and reaction time 2 h (Scheme 1).
3. Results and discussion
3.1. Characterization of ATRP initiator
Tetrafunctional zinc porphyrin initiator was obtained by
metallization of the tetrafunctional porphyrin initiator with zinc
bromide. Zinc porphyrin initiator was characterized by 1H NMR
spectroscopy, which showed no signal at chemical shift ꢁ2.82 ppm
that was ascribed to the hydrogen (NeH) in the porphyrin ring. In
addition, the chemical shift of the hydrogen (CeH) in the pyrrole
ring changed from 8.88 ppm to 8.98 ppm due to zinc coordination.
It confirmed that hydrogen (NeH) was substituted by zinc
completely (Supplementary data).
Scheme 1. Synthesis of star poly(VBCz) and poly(CzEMA).

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Y. Tao et al. / Polymer 52 (2011) 4261e4267
Fig. 1. (a) Semi-logarithmic plots and (b) Mn vs conversion plots for the synthesis of
star poly(VBCz) at 90 ꢀC.
Fig. 2. Overlay of molecular weight distribution plots obtained by SEC illustrating
distribution of star poly(VBCz) and poly(CzEMA).
increased linearly with conversion. Size exclusion chromatographic
(SEC) analysis of the star polymers was performed using refractive
index detector. Overlay of molecular weight distribution plots of
star poly(VBCz) and star poly(CzEMA) are shown in Fig. 2. As shown
in Table 1, the polydispersity indexes (PDI) of star polymers are
relatively narrow (Mw/Mn ¼ 1.09e1.32). All of these results suggest
a “living” polymerization process.
polymers which indicate that the unconverted monomer had been
removed entirely. Unfortunately, the result of 1H NMR analysis of
star polymers is hard to do calculations of molecular weights via
porphyrin core analysis, because the signal at 8.98 ppm from the
hydrogen in the pyrrole ring for star poly(VBCz) (Mn ¼ 7600 g/mol)
was obscure and no signal at 8.98 ppm for star poly(CzEMA)
(Mn ¼ 9300 g/mol) was observed. (Expansion of 1H NMR spectra
was given in Supplementary data.) We conjecture that the signal
was completely obscured by the polymer chains.
3.3. Characterization of star polymers
The 1H NMR spectra of star poly(VBCz) and star poly(CzEMA)
were illustrated in Fig. 3. For star poly(VBCz), broad peak at
0.97 ppm was assigned to the hydrogen (eCH2), signals at 1.55 ppm
are assigned to the hydrogen (eCH), broad peak at 4.88 ppm is
assigned to the hydrogen (NeCH2), and broad peaks at 6.02, 6.36,
7.02 and 7.98 ppm are assigned to the hydrogen (AreH). For star
poly(CzEMA), broad peaks at 0.14 ppm are assigned to the hydrogen
(eCH3), signals at 1.28 ppm are assigned to the hydrogen (eCH2),
broad peaks at 3.95 and 4.16 ppm are assigned to the hydrogen
(NeCH2eCH2e), and broad peaks at 7.06, 7.22 and 7.90 ppm are
assigned to the hydrogen (AreH). The signals of the hydrogen in the
vinyl group of monomers (5.2, 5.7 and 6.6 ppm for VBCz and 5.5 and
5.9 ppm for CzEMA) are absent in the 1H NMR spectrometry of star
Table 1
Monomer, reaction time, molecular weight parameters and monomer conversion of
the star polymers made by ATRP.
Monomer
Time (h)
Conversion (%)
Mn, GPC
Mw/Mn
VBCz
VBCz
VBCz
VBCz
VBCz
VBCz
VBCz
CzEMA
1
2
3
4
5
6
7
2
3.4
5.1
7.3
7600
9200
1.12
1.09
1.18
1.23
1.25
1.20
1.24
1.32
15,800
17,900
24,700
30,100
32,900
9300
8.7
11.7
14.1
15.3
5.4

Y. Tao et al. / Polymer 52 (2011) 4261e4267
4265
weak Q bands at around 560 and 600 nm. The bands in the UV
region are ascribed to carbazole group absorption, whereas the
bands in the visible are associated with Zn porphyrin absorption.
The Soret band is attributed to the singlet state, whereas the Q band
originates from the spin-triplet excited state.
3.5. Fluorescent properties
With excitation at 345 nm in DMF solution, the emission
maximum of the carbazole chromophore of the monomer is at
364 nm. However, the emission maximum of VBCz and CzEMA in
the solid state are found to be at 420 and 409 nm respectively
(figures were given in Supplementary data). Circa 50 nm red-
shifted may be caused by pep stacking interactions of carbazoles.
Similar red-shifted of other chromophores in the solid state vs in
solution has been reported in our recent work [41]. The fluorescent
properties of the star poly(VBCz) and poly(CzEMA) were investi-
gated both in solution and solid state. As shown in Fig. 5, in DMF
solution with excitation at 345 nm, the carbazole unit emits strong
fluorescence with two peaks at 353 and 366 nm, while the Zn
porphyrin emits weak fluorescence with the intensity of the Q(0,0)
peak at 607 nm and the Q(0,1) sideband at 658 nm. The weak
fluorescence could be attributed to weak excitation of Zn porphyrin
core. It should be mentioned that energy absorbed by the carbazole
chromophore is not transferred to the Zn porphyrin core effectively.
It indicates that the carbazole units of the star polymers are
completely dispersed in the dilute solution and the
pep stacking
interactions may be weakened. Excitation bands of star poly(VBCz)
and poly(CzEMA) in the solid state (figures were given in
Supplementary data) are at 400e450 nm, overlap the emission
bands of VBCz and CzEMA in the solid state. It indicates that energy
absorbed by the carbazole chromophores can be transferred
effectively to the Zn porphyrin core in the solid state because more
carbazole units come into close proximity for fluorescent resonance
energy transfer (FRET) to occur. As shown in Fig. 6, with excitation
at 345 nm in solid state, two star polymers emit obviously strong
red fluorescence with two peaks at 607 and 658 nm in visible
region. The molecular weight influences the energy transfer effi-
ciency, with lower molecular weight leading to higher efficiency.
Generally, the porphyrin chromophore in the solid state can form
aggregates that lead to fluorescence quenching. Our strategy
ensures that the Zn porphyrin chromophores are completely
wrapped by carbazole groups at the molecular level.
Fig. 3. 1H NMR spectra of star poly(VBCz) (Mn ¼ 7600 g/mol) and poly(CzEMA)
(Mn ¼ 9300 g/mol) with CDCl3 as solvent (400 MHz).
3.4. Absorption spectra
In Fig. 4, absorption spectra of two star polymers in DMF solu-
tion exhibit similar absorption pattern, in which two bands appear
at 280e350 nm, an inferior intense Soret band at 427 nm, and two
Fig. 4. Absorption spectra of the star poly(VBCz) (Mn ¼ 7600 g/mol) and star poly(-
CzEMA) (Mn ¼ 9300 g/mol) in DMF solution. The inset is a locally enlarged graph.
Fig. 5. Emission spectra of star poly(VBCz) (Mn ¼ 9200 g/mol) and star poly(CzEMA)
(Mn ¼ 9300 g/mol) in DMF solution at lex ¼ 345 nm.

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Y. Tao et al. / Polymer 52 (2011) 4261e4267
600 ꢀC and differential scanning calorimetry (DSC) from 20 to
300 ꢀC. Star poly(CzEMA) exhibited less than 5% weight loss at
297 ꢀC and star poly(VBCz) at 374 ꢀC (in Fig. 7). The thermal stability
of the styrene-type star polymer was superior to that of
methacrylate-type due to existence of benzene ring. The glass
transition was observed in the second heating scan of the DSC
curves for the star polymers, with the glass state temperatures for
star poly(CzEMA) and poly(VBCz) being 148 ꢀC and 177 ꢀC
respectively. The Tg of star poly(VBCz) is higher than that of star
poly(CzEMA), which can presumably be attributed to the rigid
molecular structure. The Tg for homopoly(CzEMA) (Mn ¼ 20900 g/
mol, PDI ¼ 3.01) was 131 ꢀC [42], the Tg of star poly(CzEMA) was
higher than that of homopoly(CzEMA). High Tg and Td are impor-
tant requisites for light-emitting materials.
4. Conclusion
ATRP of two type monomers containing a carbazole group using
zinc 5,10,15,20-tetrakis (4-(2-methyl-2-bromopropoxy) phenyl)
porphyrin as an initiator enable star poly(VBCz) and poly(CzEMA)
with controlled molecular weights and narrow polydispersity
index. The content of Zn porphyrin in the star polymers can be
regulated by the arm length. Star polymers exhibit good thermal
stability and their red light emission in the solid state due to the
effective energy transfer. Furthermore, the flexible arms of star
polymers can effectively hinder pep interaction of porphyrin cores
and prevent aggregation which would lead to fluorescent self-
quenching in the solid state. All above points support that Zn
porphyrin-cored star polymers will be promising in red-light-
emitting materials for optical devices.
Acknowledgments
Authors gratefully thank Chinese Natural Science Foundation
No. 20876101, 21076134 and 21071105, Jiangsu Province Natural
Science Foundation No. BK2009556, major project of college and
universities Jiangsu Province (08KJA430004) and project of the
development of science and technology in Suzhou (SZS0808).
Fig. 6. Emission spectra of (a) star poly(VBCz) and (b) star poly(CzEMA) in the solid
state.
3.6. Thermal stability
Appendix. Supplementary data
Thermal stability of Zn porphyrin-cored star poly(VBCz)
(Mn ¼ 9200 g/mol) and poly(CzEMA) (Mn ¼ 9300 g/mol) were
investigated by thermogravimetric analyses (TGA) from 20 to
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.polymer.2011.07.025.
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