Synthesis of amphiphilic polycyclooctene-graft-poly(ethylene glycol) copolymers by ring-opening metathesis polymerization

Article abstract of DOI:10.1016/j.reactfunctpolym.2010.04.008

In this paper, a novel monomer of 4-methyl-3-(carbamate)-carbanilic acid-4-cyclooctene ester (MCCCE) was synthesized and characterized by FTIR, NMR and ESI-MS. Polycyclooctene-graft-blocked isocyanate copolymers were prepared by the copolymerization of MCCCE and cyclooctene via ring-opening metathesis polymerization (ROMP). Amphiphilic polycyclooctene-graft-PEG copolymers were prepared by melt mixing the polycyclooctene-graft-blocked isocyanate copolymers with poly(ethylene glycol) (PEG) at 200 °C. The blocked isocyanate group on MCCCE can be dissociated to produce free isocyanate group, which will react with the end hydroxyl groups on PEG molecules. The effects of monomer-to-catalyst, monomer-to-chain transfer agent ratios on molecular weight of the copolymer were detailedly studied. The water contact angle of polycyclooctene-graft-PEG copolymer is much smaller than that of polycyclooctene.

Full text of DOI:10.1016/j.reactfunctpolym.2010.04.008

Reactive & Functional Polymers 70 (2010) 449–455
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Reactive & Functional Polymers
journal homepage: www.elsevier.com/locate/react
Synthesis of amphiphilic polycyclooctene-graft–poly(ethylene glycol)
copolymers by ring-opening metathesis polymerization
a
a
Hengchong Shi a,c, Dean Shi b, , Ligang Yin , Shifang Luan , Jie Zhao a,c, Jinghua Yin a,
*
**
a State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, PR China
b Ministry-of-Education Key Laboratory for the Green Preparation and Application of Functional Materials, Faculty of Materials Science and Engineering,
Hubei University, Wuhan 430062, China
c Graduate University of Chinese Academy of Sciences, Beijing 100049, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
In this paper, a novel monomer of 4-methyl-3-(carbamate)–carbanilic acid-4-cyclooctene ester (MCCCE)
was synthesized and characterized by FTIR, NMR and ESI-MS. Polycyclooctene-graft-blocked isocyanate
copolymers were prepared by the copolymerization of MCCCE and cyclooctene via ring-opening metath-
esis polymerization (ROMP). Amphiphilic polycyclooctene-graft–PEG copolymers were prepared by melt
mixing the polycyclooctene-graft-blocked isocyanate copolymers with poly(ethylene glycol) (PEG) at
200 °C. The blocked isocyanate group on MCCCE can be dissociated to produce free isocyanate group,
which will react with the end hydroxyl groups on PEG molecules. The effects of monomer-to-catalyst,
monomer-to-chain transfer agent ratios on molecular weight of the copolymer were detailedly studied.
The water contact angle of polycyclooctene-graft–PEG copolymer is much smaller than that of
polycyclooctene.
Received 14 March 2010
Received in revised form 14 April 2010
Accepted 16 April 2010
Available online 21 April 2010
Keywords:
Poly(ethylene glycol)
ROMP
Blocked isocyanate
Polyolefin
Ó 2010 Elsevier Ltd. All rights reserved.
Amphiphilic
1. Introduction
xy-1-cyclooctene and succinic anhydride, and then the reaction be-
tween succinic acid mono-cyclooct-4-enyl ester and poly(ethylene
Poly(ethylene glycol) (PEG) has been widely applied in materi-
als science and biotechnology [1–4] due to its low toxicity and
good biocompatibility. Generally, it has also been used to function-
alize [5,6] or blend [7,8] with some other polymers in order to im-
prove their biocompatibility. However, for polyolefins, good
biocompatible materials can not be obtained by neither surface
[9] nor bulk modification [10] because of the relatively low grafting
degree of PEG. Ring-opening metathesis polymerization (ROMP) is
a powerful and broadly applied method to synthesize many kinds
of polymers such as telechelic and end functionalized polymers
[11], nonlinear optics polymers [12], chiral polymers [13], liquid–
crystalline polymers [14], conjugated polymers [15], hole-trans-
port [16], comb polymers [17], biologically relevant polymers
[18–20], and so on. And the Grubbs’ catalysts have been exten-
sively used in the ROMP reaction [21], due to their high reactivity,
air-stability, and remarkable functional group tolerance.
glycol) monomethyl ether. However, these reaction activities were
poor, resulting in long reaction time. The other method was used an-
ionic polymerization to preparing PEG–cyclooctene, whereas the
synthesis condition of PEG–cyclooctene was more rigour.In this
article, a small molecule monomer: 4-methyl-3-(carbamate)–car-
banilic acid-4-cyclooctene ester (MCCCE) was firstly synthesized.
Then polycyclooctene-graft-blocked isocyanate copolymers were
prepared by the copolymerization of variable amount of MCCCE
and cyclooctene via ROMP reaction. Polycyclooctene-graft–PEG
copolymers were prepared by melt mixing the polycyclooctene-
graft-blocked isocyanate copolymers with PEG at 200 °C through
the reaction between the free isocyanate groups reproduced from
the dissociation of blocked isocyanate groups in MCCCE and the
end hydroxyl groups on PEG molecules. Furthermore, similar
copolymers with some other biocompatible grafts, not only PEG,
with functional groups may deactivate the Grubbs’ catalyst and
can not be directly used to undergo efficient ring-opening metathe-
sis polymerization [24] can also be easily prepared via this method.
Recently, Todd Emrick’s research group have successfully
synthesized polyethylene-graft–PEG by copolymerization of
cyclooctene and PEG–cyclooctene macromonomer through ROMP
[22,23]. The synthesis of PEG–cyclooctene was adopted by two
methods. One method was used by the reaction between 5-hydro-
2. Experimental
2.1. Materials
* Corresponding author. Tel./fax: +86 431 85262109.
** Corresponding author. Tel./fax: +86 431 85262109.
E-mail addresses: deanshi2001@yahoo.com (D. Shi), yinjh@ciac.jl.cn (J. Yin).
Cis-cyclooctene was purchased from Acros Organics Co. Ltd.
Lithium aluminum hydride (98.3%) and m-chloroperoxybenzoic
1381-5148/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.reactfunctpolym.2010.04.008

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H. Shi et al. / Reactive & Functional Polymers 70 (2010) 449–455
acid (85.3%) were purchased from Tianjin hainachuan science and
technology company. 1,5-cyclooctadiene (99%), 1-hexene (97%),
ethyl vinyl ether (99%) and Grubbs’ generation II catalyst were pur-
chased from Aldrich. Toluene diisocyanate (TDI) was purchased
from Shanghai lingfeng chemical regent Co. Ltd. Poly(ethylene gly-
col) monomethyl ether (Mn = 6000) was obtained from Shanghai
chemical regent company. Anhydrous ethanol was purchased from
Beijing chemical company. Tetrahydrofuran (THF) was distilled
with sodium and benzophenone ketyl, and dichloromethane was
distilled with calcium hydride.
(GPC) instrument. The measurements were carried out at 30 °C
using THF as the eluent with a flow rate of 1.0 mL/min. The system
was calibrated with polystyrene standards.
Mass spectrum was obtained employing A LCQ ESI-MS (Finni-
gan MAT) (ESI-MS). The spray potential was 5 kV. Full scan spectra
were acquired over the mass charge range of 50–2000 and its scan-
ning time was 2.0 s. The mass spectra were obtained by flow injec-
tion method with a flowing rate of 5 lL/min. The ion abundance
(%) was normalized on the base of one of the peaks assumed as a
reference (100%) in each spectrum.
Thermogravimetric test was carried out using a Pyris Diamond
TG/DTA thermal analyzer. The experiment was performed in the
range of 40–800 °C at a heating rate of 10 °C/min under nitrogen
atmosphere.
2.2. Characterization
1H and 13C NMR spectra were recorded on a Bruker AV 300 MHz
spectrometer.
Molecular weights and molecular weight distributions were
measured on a Waters-2414 gel permeation chromatography
Scheme 1. Synthesis route of MCCCE.
Fig. 1. FTIR spectrum of MCCCE.
Scheme 2. Polymerization of cyclooctene and MCCCE.
Scheme 3. Reaction of blocked polymer and poly(ethylene glycol).

H. Shi et al. / Reactive & Functional Polymers 70 (2010) 449–455
451
FTIR spectra of both monomers and polymers were recorded
using Bruker Vertex 70 FTIR spectrometer from 4000 to
400 cmÀ1 at a resolution of 2 cmÀ1 for 32 scans.
The determination of contact angle was conducted on a Drop
Shape Analyzer DSA100 (KRÜSS company). A droplet of water
was put on the surface of a film and the contact angle was
a
Fig. 2. 1H NMR spectrum of MCCCE.
Fig. 3. 13C NMR spectrum of MCCCE.

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H. Shi et al. / Reactive & Functional Polymers 70 (2010) 449–455
measured. Ten measurements were carried out for a single sample
and the values obtained were averaged.
was seen when the reaction was completed. The product was puri-
fied via column chromatography with 7:3 petroleum ether/ethyl
acetate on silica. The yield of MCCCE is 60%.
1H NMR d (ppm) with DMSO as solvent: 9.4 and 8.7 (two kinds
of NH), 7.0 to 7.5 (aromatic-H), 5.5–5.7 (CH2ACH@ in cyclooctene),
4.6–4.7 (ACHAO in cyclooctene), 4.0–4.1 (ACH2ACH3).
13C NMR d (ppm) with DMSO as solvent: 154.36 and 153.12
(C@O), 137.40 and 136.53 (NHAC in benzene ring), 130.20 and
129.67 (C@C in cyclooctene), 127.65, 125.50 and 114.92 (the other
carbon in benzene), 75.09 (ACAO in cylooctene), 60.16
(OACH2ACH3).
2.3. Synthesis of 4-methyl-3-(carbamate)–carbanilic acid-4-
cyclooctene ester (MCCCE)
The synthesis procedure of MCCCE was shown in Scheme 1. 5-
hydroxy-1-cyclooctene was synthesized according to the proce-
dure of literatures reported earlier [21,25].
0.0475 mol 5-hydroxyl-1-cyclooctene was dissolved in 10 mL of
dry cyclohexane and added dropwise to a solution of 0.05 mol TDI
in 30 mL of cyclohexane at 45 °C under argon atmosphere for 1 h.
The reaction stirred for an additional 12 h to obtain Monomer 3.
Then the temperature was heated to 65 °C. Anhydrous ethanol
0.05 mol was added slowly into the system for 1 h under argon
and then stirred for additional 5 h. Yellow precipitate (MCCCE)
2.4. Polymerization procedure
The ROMP route of MCCCE and cyclooctene was shown in
Scheme 2. MCCCE (0.25 mmol), cyclooctene (0.75 mmol), 1-hexene
Fig. 4. MS spectra of MCCCE.

H. Shi et al. / Reactive & Functional Polymers 70 (2010) 449–455
453
(10À5 mol) as chain transfer agent and dry dichloromethane
(0.8 mL) were added in a dry Schlenk tube under argon. In a sepa-
rate vial, Grubbs’ generation II catalyst (2 mol) was dissolved
l
with dry dichloromethane (0.2 mL). Both the monomer mixtures
and catalyst solution were subjected to two freeze/pump/thaw cy-
cles and then warmed to room temperature. The catalyst solution
was added rapidly into the monomer solution and stirred for 3 h.
Then ethyl vinyl ether (1 mL) was added to terminate the polymer-
ization, and dichloromethane was added to dilute the polymer
solution. The product was precipitated into methanol containing
0.01 wt.% butylated hydroxyl toluene (BHT) and dried under vac-
uum after filtration, and 0.12 g (70.9% yield) off-white solid
(Copolymer 1) was obtained.
The NMR of Copolymer 1 chemical shifts were assigned as
follows:
1H NMR d (ppm): 7.78 and 7.26 (two kinds of NH), 7.07, 6.59
and 6.39 (aromatic-H), 5.37 (CH2ACH@ in polymer chain), 4.84
(ACHAO in polymer chain), 4.27–4.14 (ACH2ACH3).
Fig. 5. FTIR spectrum of deblocked MCCCE.
13C NMR d (ppm): 154.09 (C@O), 137.40 and 136.68 (NHAC in
benzene ring), 131.44–129.50 (C@C in polymer chain), 121.72–
111.35 (the other carbon in benzene), 75.27 (ACAO in polymer
chain), 61.7 (OACH2ACH3).
Reaction between Copolymer 1 and poly(ethylene glycol) was
also conducted in schlenk tube as Scheme 3. Copolymer 1 and
poly(ethylene glycol) were added into schlenk tube and subjected
to five pump/charge argon cycles. Then the reaction was conducted
at 200 °C for 1 h and cooled to room temperature. The product was
washed with water to remove unreacted poly(ethylene glycol) to
constant weight.
3. Results and discussion
FTIR spectrum of MCCCE was shown in Fig. 1. The absorption
bands at 3282 cmÀ1 can be ascribed to the stretching vibration of
NAH, and the band at 1724 cmÀ1 belongs to the stretching vibra-
tion of carbonyl. And the 1456, 1491, 1606 cmÀ1 are skeleton
vibrations of benzene ring in MCCCE.
Figs. 2 and 3 are 1H NMR and 13C NMR spectra of MCCCE with
DMSO as solvent. The chemical shifts at 9.4 and 8.7 (two kinds of
NH) in Fig. 2 and 137.40 and 136.53 (NHAC in benzene ring) in
Fig. 3 demonstrated that the reactions between TDI and 5-hydro-
xyl–cyclooctene, or TDI and ethanol have been conducted.
The molecular weight of MCCCE was checked by ESI-MS. As
shown in Fig. 4A that 369.4 m/e was the quasi-molecular ion peak
of [MCCCE + Na]+. So the molecular weight of MCCCE was 346.4,
which was in accordance with the value calculated from its struc-
tural formula. Fig. 4B showed the fragmentation peak of the molec-
ular ion. Due to the fact that ESI-MS is a soft ionization process,
there were only two main peaks at 369.0 m/e and 260.9 m/e. The
peak at 369.0 m/e was attributed to [MCCCE + Na]+ and the peak
at 260.9 m/e was from the remaining part of [MCCCE + Na]+ dis-
carded with one cyclooctene group. All the above results demon-
strated that the molecule structure of MCCCE follows quite well
with that shown in Scheme 1.
The FTIR spectrum of MCCCE after being heated at 200 °C for 1 h
was given in Fig. 5. It is obvious that there is a new absorption at
2273 cmÀ1, which is the characteristic band of free NCO group. This
result indicated that the blocked isocyanate group in MCCCE could
be dissociated again at high temperature. The TG/DTA result of
MCCCE in Fig. 6 showed an original dissociation temperature of
MCCCE at 175 °C before the maximal degradation rate appeared
at 280 °C, which could be ascribed to the dissociation of block iso-
cyanate group in MCCCE.
Fig. 6. TG/DTA curve of MCCCE.
Grubbs’ generation II catalyst. Gel permeation chromatography
was used to estimate the molecular weights and molecular weight
polydispersity of the graft copolymers by using THF as eluent. The
results were presented in Table 1. As expected, the polydispersity
(Mw/Mn) of all these samples was estimated (by GPC) to be about
two.
From Table 1, it was found that molecular weight of copolymers
increased with the increase of monomer-to-catalyst ratios and the
decrease of chain transfer agent content. These results were quite
similar to the literature [26].
The structure of the copolymer was characterized by 1H NMR
and 13C NMR with CDCl3 as solvent. The 1H NMR and 13C NMR
spectra of Copolymer 1 were shown in Figs. 7 and 8, respectively.
Although the reactivity ratios of cyclooctene and MCCCE are not
equal, and the MCCCE content in the copolymer calculated by 1H
NMR was less than its addition amount, the content of blocked iso-
cyanate groups in these copolymers are still tunable by changing
the MCCCE incorporations.
It was found that there were two major transitions in the TG/
DTG curve of Copolymer 1 in Fig. 9. The low temperature transition
could be attributed to the dissociation of the blocked isocyanate
group in Copolymer 1 and its initial dissociation temperature
was 183 °C. This temperature is a little higher than that 175 °C
for MCCCE monomer, which indicates that the stability of the
Graft Copolymers 1–9 were prepared by ROMP with the appro-
priate ratio of cyclooctene to MCCCE in dichloromethane, using

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H. Shi et al. / Reactive & Functional Polymers 70 (2010) 449–455
Table 1
ROMP of MCCCE and cyclooctene using Grubbs II catalysts.
Polymers [M]/
[M]/
[hexene]
mMCCCE
(%)
Mn  10À4 PDI
MMCCCE
(%)
[Cat]
1
2
3
4
5
2
6
2
7
8
9
250:1
500:1
750:1
500:1
500:1
500:1
500:1
500:1
500:1
500:1
500:1
100:1
100:1
100:1
25:1
25
25
25
25
25
25
25
25
50
75
100
3.89
4.48
5.29
1.27
2.55
4.48
8.06
4.48
12.49
11.78
6.19
2.53 24.21
2.30 22.77
2.46 24.23
1.64 23.32
2.07 23.64
2.30 22.77
2.89 22.03
2.30 22.77
2.35 44.08
2.27 72.27
2.58 98.60
50:1
100:1
200:1
100:1
100:1
100:1
100:1
Fig. 9. TG/DTA curve of Copolymer 1.
Fig. 7. 1H NMR spectrum of Copolymer 1.
Fig. 10. FTIR spectra of Copolymer 1 and polycyclooctene-graft–PEG.
attributed to OAH and CAO stretch vibration in poly(ethylene gly-
col) chains. This demonstrated that poly(ethylene glycol) indeed
reacted with Copolymer 1 and formed polycyclooctene-graft–PEG
graft copolymer.
The contact angles of polycyclooctene-graft–PEG and polycyc-
looctene were 68.06o and 87.28o, respectively. The hydrophilic
molecule chains in polycyclooctene-graft–PEG results in the lower
contact angle.
4. Conclusion
In this paper, a novel monomer of 4-methyl-3-(carbamate)–car-
banilic acid-4-cyclooctene ester (MCCCE) was synthesized and its
structure was characterized by FTIR, 1H NMR and 13C NMR. Molec-
ular weight obtained from ESI-MS was 346.4, which was in accor-
dance with the value calculated from its structural formula. FTIR
results of MCCCE heated at 200 °C for 1 h produced a new peak
at 2273 cmÀ1, which demonstrated that it can be dissociated again
to produce free isocyanate group. MCCCE can easily copolymerize
with cyclooctene to form polycyclooctene-graft-blocked isocya-
nate copolymers by ring-opening metathesis polymerization with
Grubbs’ generation II catalyst. The molecular weight of the copoly-
mer increased with either the increase of monomer-to-catalyst ra-
tio or the increase of monomer-to-chain transfer agent ratio.
Polycyclooctene-graft–PEG copolymer was prepared by melt mix-
ing the above polycyclooctene-graft-blocked isocyanate copolymer
Fig. 8. 13C NMR spectrum of Copolymer 1.
blocked isocyanate group in Copolymer 1 is higher than that in
MCCCE monomer. The other transition was the degradation of
molecular skeleton and the temperature of maximum degradation
rate was 463 °C.
Fig. 10 is the FTIR spectrum of Copolymer 1 and polycycloocten-
e-graft–PEG graft copolymer obtained from reaction between
Copolymer 1 and poly(ethylene glycol). Compared to that of
Copolymer 1, two new main peaks appeared in polycyclooctene-
graft–PEG copolymer at 3430 and 1110 cmÀ1 which should be

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Acknowledgments
The authors gratefully thank for the financial supports by Na-
tional Natural Science Foundation of China (Grant Nos. 50833005
and 50920105302). The work has also been carried out in the
framework of the Research Cooperation Agreement between the
Chinese Academy of Sciences (CAS) and the National Research
Council (CNR) of Italy.
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