Synthesis and characterization of cyclohexene oxide functional polystyrene macromonomers by ATRP and their use in photoinitiated cationic polymerization

Article abstract of DOI:10.1016/j.reactfunctpolym.2009.09.010

In this study, a novel well-defined macromonomer of epoxy end-functionalized polystyrene was synthesized by atom transfer radical polymerization (ATRP). The compound 3-cyclohexenylmethyl-2-bromopropanoate was synthesized by the condensation of 3-cyclohexe

Full text of DOI:10.1016/j.reactfunctpolym.2009.09.010

Reactive & Functional Polymers 70 (2010) 28–34
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Reactive & Functional Polymers
journal homepage: www.elsevier.com/locate/react
Synthesis and characterization of cyclohexene oxide functional polystyrene
macromonomers by ATRP and their use in photoinitiated cationic polymerization
b
c
c
Mustafa Degirmenci a, , Oner Izgin , Aslisah Acikses , Nasrettin Genli
*
a Harran University, Science Faculty, Department of Chemistry, Sanliurfa 63190, Turkey
b Mikron’s Micronised Mineral Industry Trade Co. Umraniye, Istanbul 34776, Turkey
c Firat University, Science Faculty, Department of Chemistry, Elazig 23000, Turkey
a r t i c l e i n f o
a b s t r a c t
Article history:
In this study,
a
novel well-defined macromonomer of epoxy end-functionalized polystyrene
Received 18 July 2009
Received in revised form 25 September
2009
Accepted 26 September 2009
Available online 3 October 2009
was synthesized by atom transfer radical polymerization (ATRP). The compound 3-cyclohexenylmeth-
yl-2-bromopropanoate was synthesized by the condensation of 3-cyclohexene-1-methanol with
2-bromopropanoyl bromide. Subsequently, the epoxidation of the obtained 3-cyclohexenylmethyl-2-
bromopropanoate using 3-chloroperoxybenzoic acid results in a new epoxy functional ATRP initiator.
The ATRP of styrene (St) in bulk at 110 °C, by means of this initiator in conjunction with the cuprous com-
plex Cu(I)Br/bipyridine, yields a well-defined macromonomer of polystyrene with an epoxy end group.
GPC, IR, and 1H NMR analyses revealed that a low-polydispersity polystyrene with the desired function-
ality at the end of the chain was obtained. The photoinduced cationic polymerization of this macromo-
nomer yielded graft and block copolymers.
Keywords:
Atom transfer radical polymerization (ATRP)
Functional polymer
Macromonomer
Ó 2009 Elsevier Ltd. All rights reserved.
Free radical promoted cationic
polymerization
Copolymerization
1. Introduction
satile methods in CRP is atom transfer radical polymerization
(ATRP) because of its relatively mild reaction conditions, the avail-
Recently, the attention of both academic and industrial fields
has been attracted to the design and synthesis of materials with
novel properties. Various polymers with end-functional groups
have been synthesized as precursors of block and graft copolymers,
star polymers, and polymer networks [1]. Macromonomers are lin-
ear polymers or oligomers carrying polymerizable functional
groups at their chain end(s). The chain end(s) can include unsatu-
rated groups, which can participate in radical or ionic polymeriza-
tions, heterocycles active in ring-opening polymerizations, and
functional groups that can participate in polycondensation reac-
tions. Depending on the type of end-functionality, the polymeriza-
tion of macromonomers results in graft copolymers or networks.
There have been many publications on preparing macromonomers
via various methods including anionic, cationic, and radical poly-
merizations, as well as chemical modifications of polymer ends
[1–7].
ability of appropriate monomers, initiators, and catalysts, and in
particular its versatility in the synthesis of polymers with predict-
able molecular weights, low polydispersities, specific functional-
ities and various architectures [14–18]. Due to the radical nature
of ATRP, a wide range of functional monomers can be polymerized,
yielding polymers with pendant functional groups. Therefore, var-
ious functional monomers including styrenes, (meth)acrylates and
others have been (co)polymerized in a controlled fashion by ATRP
[10,19,20].
We have previously prepared types of functional polymers of
poly(
e-caprolactone) [21,22], polystyrene [23,24], and poly(methyl
methacrylate) [25] that have the potential to initiate light-induced
free radical polymerization by CRP techniques such as ring-open-
ing polymerization and ATRP. These polymers were also used in
so-called free radical promoted cationic polymerization to yield
block copolymers of structurally different monomers such as
In recent years, there have been many developments in the
synthesis of functional polymers with controlled architecture and
site-specific functionality by applying controlled radical polymeri-
zation (CRP) techniques [8–13]. One of the most powerful and ver-
cyclohexene oxide (CHO) and e-caprolactone (CL). There are many
reports on the use of photoinitiated cationic polymerization for the
preparation of block copolymers [26–32]. However, the corre-
sponding graft copolymerization via a similar photoinduced pro-
cess has received little study [33,34]. It occurred to us that the
macromonomer method involving CHO end-functional polymers
might be particularly useful because photochemically generated
* Corresponding author. Tel.: +90 414 3440020x1261; fax: +90 414 3440051.
E-mail address: mustafa@harran.edu.tr (M. Degirmenci).
1381-5148/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.reactfunctpolym.2009.09.010

M. Degirmenci et al. / Reactive & Functional Polymers 70 (2010) 28–34
29
cationic species are quite reactive towards these groups. In this
article, we present the results of a study of the preparation of
CHO end-functional macromonomers via ATRP of styrene mono-
mer using a new CHO-functional initiator and a Cu(I)Br/bipyridine
catalyst system.
(cmꢀ1): 3024 (C@C–H stretch), 1739 (C@O ester band), 1651 (C@C
stretch).
2.3. Synthesis of cyclohexene oxide (CHO) functional ATRP initiator
(CHO–Br)
Epoxidation of the 3-cyclohexenylmethyl-2-bromopropanoate
was performed under inert atmosphere at 0 °C. The obtained 3-
cyclohexenylmethyl-2-bromopropanoate (4 g, 16.18 mmol), sodi-
umbicarbonate (5.437 g, 64.72 mmol), 3-chloroperoxybenzoic acid
(5.58 g, 32.37 mmol) and 20 mL of dry CH2Cl2 were added into a
100-mL three-necked round-bottom flask fitted with a condenser,
a magnetic stirrer, and a nitrogen inlet–outlet. The flask was placed
in an ice-water bath and stirred for 30 min. Then, the mixture was
allowed to reach room temperature and stirred at that temperature
for 2 h. After the reaction, the reaction mixture was added into
100 mL of water, and then extracted several times with CH2Cl2. Fi-
nally, the solution was dried with MgSO4, and the solvent was re-
moved by vacuum distillation. A yellowish oily product was
obtained. Yield: 2.25 g, 53%.
C10H15O3Br: (263,130): Calcd. C, 45.64%; H, 5.70%, Found: C,
45.12%; H, 5.54%. 1H NMR (acetone-d6, d/ppm): 4.73–4.42 (q, 1H,
CH–Br), 4.41–3.86 (m, 2H, OCH2), 3.23–3.00 (m, 2H, CH–O–CH,
epoxide protons), 2.24–1.94 (m, 1H, OCH2CH), 1.82–1.62 (d, 3H,
CH3CH), 1.60–1.00 (m, 6H, methylene protons of cyclohexene oxide
group). FT-IR (cmꢀ1): 1739 (C@O ester band), 920 (epoxide band),
2. Experimental
2.1. Materials
Styrene (St) (Fluka) and cyclohexene oxide (CHO) (Aldrich)
were distilled over calcium hydride (CaH2) and stored in a refriger-
ator under nitrogen before use. The compounds 3-cyclohexene-1-
methanol (Aldrich), 2-bromopropanoyl bromide (Aldrich),
3-chloroperoxybenzoic acid (Aldrich), and sodium bicarbonate
(NaHCO3) (Merck) were used as received. The compound 2,2-dime-
thoxy-2-phenyl acetophenone (DMPA) (Irgacure 651), the photo-
initiator, was purchased from Ciba Specialty Chemicals and used
as received without further purification. Dichloromethane (CH2Cl2)
(Lab-scan) pyriꢀdine (Lab-scan), diphenyliodonium hexafluorophos-
phate (Ph2I+PF6 ) (Fluka), CuBr (Aldrich), 2,20-bipyridine (Merck)
and all other solvents and chemicals were used as received.
2.2. Synthesis of 3-cyclohexenylmethyl-2-bromopropanoate (CH–Br)
For this synthesis, 3-cyclohexene-1-methanol (5.02 mL,
44.6 mmol), pyridine (5.40 mL, 66.9 mmol), and 30 mL dry CH2Cl2
were added to a two-necked round-bottom flask fitted with a mag-
netic stirrer, nitrogen inlet–outlet and an addition funnel contain-
ing 2-bromopropanoyl bromide (7.07 mL, 66.90 mmol) and 5 mL
dry CH2Cl2. The flask was placed in an ice-water bath. The solution
of 2-bromopropanoyl bromide was added dropwise over a period
of 1 h under nitrogen. The mixture was stirred at 0 °C for 30 min.
The mixture was then allowed to reach room temperature and stir-
red at that temperature overnight. The solution was washed with
0.2 N HCl and several times with water. Finally, the solution was
dried with MgSO4, and the solvent was removed by vacuum distil-
lation. A yellowish liquid product was obtained. Yield: 9.97 g, 91%.
C10H15O2Br: (247,131): Calcd. C, 48.60%; H, 6.07%, Found: C,
48.12%; H, 6.01%. 1H NMR (acetone-d6, d/ppm): 5.92–5.52 (m, 2H,
HC@CH), 4.75–4.41 (q, 1H, CH–Br), 4.28–3.82 (m, 2H, OCH2),
2.16–1.96 (m, 1H, OCH2CH), 1.84–1.65 (d, 3H, CH3CH), 1.51–1.16
(m, 6H, methylene protons of cyclohexene oxide group). FT-IR
2.4. Synthesis of cyclohexene oxide end-functional macromonomer of
polystyrene by atom transfer radical polymerization (CHO-PSt)
A Schlenk tube equipped with a magnetic stirrer was used. The
system was vacuumed and back-filled with nitrogen several times.
The catalyst (CuBr), ligand bipyridine (bpy), initiator (CHO–Br), and
monomer (St) were introduced under inert atmosphere. The tube
was placed in an oil bath warmed at 110 °C and stirred at that tem-
perature. After a given time (see Table 1), the mixture was diluted
with THF and poured into ten-fold methanol. The macromonomer
(CHO-PSt) was collected after filtration and dried at 40 °C in vac-
uum overnight. In order to remove the complex salt from the poly-
mer, it was redissolved in THF and passed through an alumina
column, followed by precipitation in methanol.
1H NMR (acetone-d6, d/ppm): 7.52–6.39 (m, 5H, Ar–H), 4.60 (q,
1H, CH–Br), 3.84–3.63 (m, 2H, OCH2), 3.23–3.00 (m, 2H, CH–O–CH,
Table 1
Synthesis of CHO end-functional macromonomers of PSt by ATRPa using CHO–Br as initiator.
[I] ꢁ 10ꢀ2 (mol Lꢀ1
)
Time (min)
Conversion (%)
Mn
Mn
Mw/Mn
Mn
H
b
Run
theo
GPC
NMR
1
2
3
9.7
28.9
57.9
180
90
60
45
39
59
4500
1490
1160
3650
1590
970
1.21
1.27
1.24
4200
1920
1025
a
Temperature 110 °C, [St]0 = 8.75 mol Lꢀ1(in bulk), [I]:[CuBr]:[Bpy] = 1:1:3.
Determined by GPC according to PSt standards.
b
Table 2
Photoinitiated cationic polymerization of CHO-PSt macromonomera.
Run
Photoinitiaton type
Activator (mol Lꢀ1
–
)
Wavelength (k, nm)
Mn
Mw/Mn
1
2
3
Direct
Promoted
Sensitized
300
350
350
3940
4110
6200
1.60
1.44
1.75
DMPA (5810–3
)
Anthracene (5 ꢁ 10ꢀ3
)
Conversions were calculated using the following formula: Conv.% = (W – W0)/W ꢁ 100 ; where W and W0 are the total polymer obtained and unreacted macromonomer.
Macromonomer: 200 g Lꢀ1 with Mn = 1590; onium salt, Ph2I+PF6ꢀ: 5 ꢁ 10ꢀ3 mol Lꢀ1; temperature: room temperature; solvent: CH2Cl2; irradiation time: 5 h; conversions:
a
>99%.

30
M. Degirmenci et al. / Reactive & Functional Polymers 70 (2010) 28–34
Table 3
Photoinitiated cationic polymerization CHO-PSt macromonomer with cyclohexene oxide (CHO) monomera.
Run
CHO (mol Lꢀ1
)
Irradiation time (min)
Yieldb (%)
Mn
Mw/Mn
Copolymer compositionc (mol, %) PSt PCHO
1
2
3
0.85
1.65
4.95
6.60
9.90
70
60
45
25
20
52
50
45
23
37
6800
4700
3200
2500
4600
1.75
1.89
1.90
2.14
1.95
69 31
65 35
21 79
19 81
23 77
4
5d
Macromonomer: 200 g Lꢀ1 with Mn = 1590; onium salt, Ph2I+PF6ꢀ: 5 ꢁ 10ꢀ3 mol Lꢀ1; temperature: room temperature; solvent: CH2Cl2; irradiation wavelength:
a
k = 300 nm.
b
CHO conversion.
Calculated from 1H NMR spectra of samples.
Bulk.
c
d
O
O
Br
OH
O
Br
O
Pyridine
1
2
Br
+
CH-Br
O
Br
Br
O
O
CHO-Br
3-chloroperoxybenzoic acid
O
CH-Br
Scheme 1. Synthesis of cyclohexene oxide (CHO) functional ATRP initiator.
epoxide protons), 2.20–1.81 (m, 3H, OCH2CH, CH3CH and Ar–CH),
1.80–1.21 (m, 10H, methylene protons of cyclohexene oxide group
and styrene segment in polymer chain).
2.5. Photopolymerization
Photopolymerizations were carried out both in bulk and solu-
tion. Appropriate solutions of macromonomers containing calcu-
lated amounts of other components, shown in Tables 2 and 3,
were placed in Pyrex or quartz tubes and degassed with nitrogen
prior to irradiation by
a merry-go-round type photoreactor
equipped with 16 lamps emitting light nominally at k = 300 or
k = 350 nm and a cooling system. At the end of the given time
(see Tables 2 and 3 again), the polymers were poured into cold
methanol, filtered, dried, and weighed. Conversions were deter-
mined gravimetrically.
2.6. Characterization
Fourier transform infrared (FT-IR) spectra were recorded on a
Perkin–Elmer spectrum RXI FT-IR spectrophotometer. 1H NMR
spectra were measured on a Bruker 250 MHz spectrometer at
ambient temperature. Gel permeation chromatography (GPC)
chromatograms were obtained using
a Waters instrument
equipped with a R410 differential refractometer and 600E pump
and with THF as the eluent, at a flow rate of 1.0 mL/min. Molecular
weights were calculated using monodisperse polystyrene
standards.
3. Results and discussion
It has been shown that CuBr/bipyridine complex is very effec-
tive for ATRP in conjunction with alkyl halides [15]. The objective
of this work was to design an initiator with cyclohexene oxide
(CHO) containing alkyl bromide, so as to produce CHO end-func-
Fig. 1. 1H NMR spectra of CHO–Br (a) and CHO-PSt (Table 1, run 2) (b) in acetone-
d6.

M. Degirmenci et al. / Reactive & Functional Polymers 70 (2010) 28–34
31
NMR spectra of related compounds, only the peak observed at
5.92–5.52 ppm due to the vinyl protons completely disappeared
in the spectrum of CHO–Br (Fig. 1a). Instead, new signals appeared
at 3.23–3.00 ppm, which were assigned to the protons of the CHO
moiety. Moreover, the FT-IR spectral analysis also supports this re-
sult (see supporting information). For example, the peak at
1651 cmꢀ1 due to the C@C stretch and the peak at 3024 cmꢀ1
due to the C@C–H stretching vibration observed in the spectrum
of CH–Br spectrum completely disappeared in the spectrum of
CHO–Br, and a new peak at 920 cmꢀ1, which was assigned to the
epoxide band was clearly observed. All these results indicated suc-
cessful epoxidation and the formation of the new CHO-functional
ATRP initiator.
The ATRP of styrene (St) was performed in bulk at 110 °C by
means of an ATRP initiator (CHO–Br) in conjunction with a cuprous
complex Cu(I)Br/bpy. In view of the reported role of halide groups
as initiators in ATRP, this reaction was expected to produce a poly-
mer containing a cyclohexene oxide (CHO) group on one chain end
(CHO-PSt) derived from the initiator as shown in Scheme 2.
As can be seen from Table 1, the measured and calculated Mn
values are in good agreement, indicating that the photoinitiator
added to the solution generates one growing end. By modifying
the initiator concentration and the polymerization time, CHO
end-functional macromonomers with various molecular weights
and low polydispersities were obtained. A control experiment in
the absence of styrene monomer was performed under similar
ATRP conditions in order to check whether the epoxide group
(CHO) remained intact during the ATRP processes. After 2 h of reac-
tion time, the product was isolated and characterized. The spectral
characterization (FT-IR and 1H NMR spectral measurements) of the
product obtained after ATRP clearly showed the same results as
CHO–Br before ATRP. This result indicated that the CHO end group
was not affected under polymerization conditions.
Fig. 2. GPC traces of polystyrene (Table 1, run 2) (a) and poly(cyclohexene oxide)-g-
polystyrene (Table 3, run 2) (b).
tionalized polystyrenes and subsequently use them as a precursor
for photoinitiated cationic polymerization. The ATRP initiator was
prepared in two steps, as shown in Scheme 1. In the first step, 3-
cyclohexenylmethyl-2-bromopropanoate (CH–Br) was synthesized
by the condensation of 3-cyclohexene-1-methanol with 2-bromo-
propanoyl bromide. In the second step, the epoxidation of obtained
CH–Br using 3-chloroperoxybenzoic acid results in a new CHO-
functional ATRP initiator (CHO–Br).
The structures of initiators with cyclohexene and cyclohexene
oxide end groups (CH–Br and CHO–Br) were confirmed by elemen-
tal analyses and spectroscopic investigations. The 1H NMR spectra
of the CH–Br (see supporting information) and of the CHO–Br
(Fig. 1a) display the signals characteristic of the corresponding seg-
ments. The characteristic peak at 5.92–5.52 ppm observed in the
spectrum of CH–Br was ascribed to the protons at the double bond
(–CH@CH–) of the cyclohexene ring. The other characteristic reso-
nances originating from the CH–Br compound at 4.75–4.41 ppm,
4.28–3.82 ppm, 2.16–1.96 ppm, 1.84–1.65 ppm, and 1.51–
1.16 ppm, assigned to the –CH–Br, –OCH2–, –OCH2CH–, –CH3CH–,
and –CH2– groups, respectively, were still present in the 1H NMR
spectrum of CHO–Br (Fig. 1a). As can be clearly seen from the 1H
The theoretical molecular weights (Mn theo) of the CHO-PSt sam-
ples were calculated by the following equation:
Mn theo ¼ ½Mꢂ0=½Iꢂ0 ꢁ Mn St ꢁ Conversion þ Mn CHO—Br
where [M]0 and [I]0 are the initial molar concentrations of monomer
and initiator (CHO–Br), and Mn
and Mn CHO–Br are the molecular
St
weights of the monomer (styrene) and initiator, respectively. The
molecular weights (Mn H NMR) can be calculated from the ratio of
aromatic protons of styrene in the CHO-PSt polymer to b protons
of the cyclohexene oxide end group in the 1H NMR spectrum. The
equation is shown below:
O
O
Br
Br
O
O
CHO-PSt
n Styrene
CuBr/bpy
110 oC, in bulk
n
O
O
3
CHO-Br
Scheme 2. Synthesis of cyclohexene oxide (CHO) end-functional polystyrene macromonomer.
O
O
Br
Ph2I+PF6
O
-
m
O
4
n
O
Br
hν, 300 nm
O
n
CHO-PSt
PCHO-PSt comb-shaped polymer
Scheme 3. Photoinitiated cationic polymerization of polystyrene macromonomer.

32
M. Degirmenci et al. / Reactive & Functional Polymers 70 (2010) 28–34
O
C
O
C
O
O
C
O
C
O
hν
350 nm
+
5
6
7
O
C
O
O
Ph2I+
C +
O
PhI
Ph
+
+
+
O
C +
O
PCHO-PSt comb-shaped polymer
CHO-PSt
+
Scheme 4. Photolysis of 2,2-dimethoxy-2-phenyl acetophenone in the presence of diphenyliodonium salt.
ðI7:52ꢀ6:39=5
Þ
Þ
onium salt is transparent, the light is absorbed only by DMPA.
Mn H NMR
¼
ꢁ Mn St þ Mn CHO—Br
The photochemically generated 2,2-dimethoxy benzyl radicals re-
duce the iodonium salt to yield corresponding carbocations [37]
(reaction 6) capable of initiating cationic polymerization of the
macromonomer.
ðI3:23ꢀ3:00=2
where I7.52ꢀ6.39 is the integral of the signals at 7.52–6.39 ppm,
I3.23ꢀ3.00 is the integral of the signals at 3.23–3.00 ppm, Mn is
the molecular weight of styrene and Mn
St
is the molecular
CHO–Br
weight of CHO–Br.
Fig. 2a shows the GPC trace of cyclohexene oxide end-chain
functional macromonomer (CHO-PSt). It is unimodal and narrow,
indicating that polymerization was performed in a controlled man-
ner and that no side reactions occurred during the ATRP process.
In the 1H NMR spectrum of the macromonomer (CHO-PSt) (Ta-
ble 1, run 2) can be found not only the specific signals of polysty-
rene (PSt) but also absorptions belonging to the rest of the
initiators. As can be clearly seen from that spectrum, the epoxy
end group of the polymer was conserved under the polymerization
conditions (Fig. 1b).
The obtained CHO end-functional macromonomers were used
as precursors in the photoinitiated cationic polymerization. Table
2 shows the types of photoinitiation used in our work. As can be
seen from Scheme 3, homopolymerization of macromonomers pro-
vides comb-shaped polymers with a very high branch density
[35,36].
All the types of photoinitiation systems yielded polymers with
high conversion (>99%) and basically the same structure. As ex-
pected, the molecular weight and molecular weight distribution
of the obtained polymers were slightly higher than those of the
macromonomer (Scheme 3). Although the conversions are so high,
the molecular weights of the polymers are quite low. This is prob-
ably due to the chain entanglement and steric hindrances of high
branch polymers obtained during photoinitiation. These effects
prevent the initiator from reaching the macromonomer’s active
site to initiate polymerization and leads to short chains even at
very long reaction times. Photoinitiated cationic polymerization
by direct irradiation of the iodonium salt at 300 nm presents some
limitations for the potential use of PSt macromonomers because of
their overlapping tail absorptions. Therefore, we have also em-
ployed indirect ways, namely free radical promoted photosensiti-
zation, to provide working conditions for photoinitiated cationic
polymerization at a broad wavelength range.
In the radical promoted cationic polymerization, DMPA was
used as the radical source, as shown in Scheme 4. The photolysis
of DMPA results in
a-cleavage and 2,2-dimethoxy benzyl (strong
electron donor), and benzoyl (electron withdrawing) radicals are
formed according to reaction 5. When irradiated in the presence
of an onium salt such as diphenyl iodonium at 350 nm where
Fig. 3. 1H NMR spectra of poly(cyclohexene oxide)-polystyrene graft copolymer
(Table 3, run 2) (a) and poly(cyclohexene oxide)-polystyrene comb-shaped polymer
(Table 2, run 2) (b) in CDCl3.

M. Degirmenci et al. / Reactive & Functional Polymers 70 (2010) 28–34
33
*
hν
8
9
350 nm
*
+
Ph2I+
+
PhI + Ph
+ H+ + R
+ R-H
10
11
H+
CHO-PSt
PCHO-PSt comb-shaped polymer
+
Scheme 5. Photolysis of anthracene in the presence of diphenyliodonium salt.
O
O
O
y
-
x
Ph2I+PF6
O
y CHO-PSt
x
12
+
Br
hν, 300 nm
O
n
CHO
PCHO-g-PSt
Scheme 6. Synthesis of poly(cyclohexene oxide)-g-polystyrene.
Fig. 3b shows the 1H NMR spectrum of the poly(cyclohexene
oxide)-polystyrene comb-shaped polymer (Table 2, run 2). Not
only the specific signals of PCHO and PSt segments are visible,
but also absorptions belonging to the rest of the initiator fragment.
In earlier studies on photoinitiated cationic polymerization
using anthracene as a sensitizer it was shown that the electron
transfer, governed by energetic and thermodynamic consider-
oxide)-polystyrene graft copolymer with random sequences of
the following structure (PCHO-g-PSt) was formed (Scheme 6).
Fig. 3b shows the GPC chromatogram of the graft copolymer
(PCHO-g-PSt) that was formed. Notably, no peak pertaining to
the residual homopolymer was detected. The graft copolymer
structures were also assigned by means of NMR spectral measure-
ments. As can be seen the 1H NMR spectrum of the graft copolymer
displays typical signals at 3.36 ppm of OCHCHO (PCHO) and 7.20–
6.25 ppm of aromatic protons (PSt).
ations, was the dominant process. The magnitude of the free
DG
.
energy for the electron transfer should have been 10 kJ molꢀ1
The
D
G value (ꢀ193 kJ molꢀ1) suggests that electron transfer from
singlet anthracene to iodonium ions is quite favorable [37].
Anthracene radical cation or Brønsted acid formed from the hydro-
gen abstraction reaction may initiate the polymerization (Scheme
5).
4. Conclusions
A new ATRP initiator with a CHO-functional group (CHO–Br)
was synthesized by epoxidation of 3-cyclohexenylmethyl-2-
bromopropanoate in the presence of 3-chloroperoxybenzoic acid.
The ATRP of styrene monomer using CHO–Br initiator formed a
well-defined PSt macromonomer possessing CHO end groups.
The obtained CHO end-functional PSt macromonomer was em-
ployed in photoinitiated cationic (co)polymerization using diphe-
nyliodonium salt. Photoinitiation of cationic polymerizations can
be efficiently achieved by using the iodonium salt at 300 nm as
well as at wavelengths of about 350 nm with the aid of sensitizers
and free radical sources.
Polystyrene macromonomer (CHO-PSt) was used as a comono-
mer in the copolymerization with CHO under similar conditions to
those applied for the polymerization of the CHO-PSt macromono-
mer itself. Typical results concerning photochemically induced cat-
ionic copolymerization of CHO with CHO-PSt macromonomer at
room temperature are shown in Table 3. As can be seen, the con-
centration of the CHO comonomer influences the composition of
the graft copolymer. The composition of the copolymers PCHO-g-
PSt was determined from 1H NMR spectra using the integrated
peak ratio of the aromatic protons of styrene (6.25–7.20 ppm) in
the PSt segment to the OCHCHO protons in the PCHO segment
(3.36 ppm). The content of PSt units in a copolymer X (mol %)
was calculated using the following formula:
Acknowledgements
ðI7:20ꢀ6:25=5Þ
The authors would like to thank Harran University, the Scien-
tific Research Council (HÜBAK) and Firat University Scientific Re-
search Projects Unit (FÜBAP) for financial support.
XPSt
¼
ꢁ 100
ðI7:20ꢀ6:25=5Þ þ ðI3:36=2
Þ
where I7.20ꢀ6.25 is the integral of the aromatic proton signals at
7.20–6.25 ppm, and I3.36 is the integral of the OCHCHO proton sig-
nals at 3.36 ppm.
Appendix A. Supplementary data
Using CHO-PSt macromonomer as the comonomer allowed for a
rather simple incorporation of PSt side chains into poly(cyclohex-
ene oxide) (PCHO) backbone. In this way, poly(cyclohexene
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.reactfunctpolym.2009.09.010.

34
M. Degirmenci et al. / Reactive & Functional Polymers 70 (2010) 28–34
[20] Y. Chen, M. Sone, K. Fuchise, R. Sakai, R. Kakuchi, Q. Duan, J. Sun, A. Narumi, T.
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