Synthesis of a norbornene monomer having cyclic carbonate moiety based on CO2 fixation and its transition metal-catalyzed polymerizations

Article abstract of DOI:10.1002/pola.24176

A norbornene monomer bearing cyclic carbonate moiety (NB-CC) was successfully synthesized from the corresponding precursor having epoxy moiety by its reaction with carbon dioxide under atmospheric pressure, which was efficiently catalyzed by lithium bromide. NB-CC underwent the ring-opening metathesis polymerization (ROMP) catalyzed by a ruthenium carbene complex to give the corresponding poly-(norbornene), of which side chain inherited the cyclic carbonate moiety from the monomer without any deterioration. The same ROMP system was applicable to the copolymerization of NB-CC and 5-butyl-2-norbornene (BNB), which afforded the corresponding copolymer with a composition ratio same as a feed ratio. In addition, by using a catalytic system consisted of palladium (II) acetate/tricyclohexylphosphine/triphenylcarbenium tetrakis(pentafluorophenyl)borate, the copolymerization of NB-CC and BNC proceeded successfully in a vinyl addition polymerization mode to give the corresponding poly(norbornene) having CC moiety in the side chain.

Full text of DOI:10.1002/pola.24176

Synthesis of a Norbornene Monomer Having Cyclic Carbonate Moiety
Based on CO2 Fixation and Its Transition Metal-Catalyzed Polymerizations
ATSUSHI SUDO, HIDETADA MORISHITA, TAKESHI ENDO
Molecular Engineering Institute, Kinki University, 11-6 Kayanomori, Iizuka, Fukuoka 820-8555, Japan
Received 20 April 2010; accepted 6 June 2010
DOI: 10.1002/pola.24176
Published online in Wiley InterScience (www.interscience.wiley.com).
ABSTRACT: A norbornene monomer bearing cyclic carbonate
moiety (NB-CC) was successfully synthesized from the corre-
sponding precursor having epoxy moiety by its reaction with
carbon dioxide under atmospheric pressure, which was effi-
ciently catalyzed by lithium bromide. NB-CC underwent the
ring-opening metathesis polymerization (ROMP) catalyzed by a
ruthenium carbene complex to give the corresponding poly-
(norbornene), of which side chain inherited the cyclic carbon-
ate moiety from the monomer without any deterioration. The
same ROMP system was applicable to the copolymerization of
NB-CC and 5-butyl-2-norbornene (BNB), which afforded the
corresponding copolymer with a composition ratio same as a
feed ratio. In addition, by using a catalytic system consisted
of palladium (II) acetate/tricyclohexylphosphine/triphenylcarbe-
nium tetrakis(pentafluorophenyl)borate, the copolymerization of
NB-CC and BNC proceeded successfully in a vinyl addition poly-
merization mode to give the corresponding poly(norbornene)
C
V
having CC moiety in the side chain.
2010 Wiley Periodicals,
Inc. J Polym Sci Part A: Polym Chem 48: 3896–3902, 2010
KEYWORDS: copolymerization; cyclic carbonate; functionaliza-
tion of polymers; norbornene; ROMP
INTRODUCTION Norbornene and its derivatives are attrac-
tive cycloolefinic monomers, of which ring-opening metathe-
sis polymerization (ROMP)1 and transition metal-catalyzed
addition polymerization2 give the corresponding polymers
that inherit the rigid cyclic structures from the monomers to
exhibit the outstanding properties, such as high thermal sta-
bility, high transparency, low birefringence, and low-dielec-
tric constant. ROMP has been extensively investigated so far,
leading to the current prosperity of the field, where various
catalysts have been developed to achieve tailored synthesis
of poly(norbornene)s with defined structures from a wide
range of norbornene-derivatives.3,4 On the other hand, the
addition polymerization of norbornene derivatives has
attracted growing attention recently, because it gives the cor-
responding poly(norbornene)s without CAC double bonds
and thus highly durable even in the presence of oxygen. Vari-
ous transition metal catalysts involving nickel,5 palladium,6
cobalt,7 iridium,8 titanium,9 and zirconium10 have been
developed for the addition polymerization of norbornenes.
hand, there have been only a limited number of reports on
successful addition polymerizations of norbornene-deriva-
tives having functional groups, such as silyl,11 ester,12
hydroxyl,13 and carboxyl groups.13
Previously, we reported a new synthesis of a norbornene de-
rivative having epoxy group (2-bicyclo[2.2.1]hept-5-en-2-yl
oxirane; NB-EP) and its palladium-catalyzed addition poly-
merization.14 The polymerization gave the corresponding
poly(norbornene) having epoxy moiety in the side chain,
which is potentially applicable to various side chain modifi-
cations and crosslinking reactions to give the corresponding
functionalized poly(norbornene)s and networked poly(nor-
bornene)s. Besides the attractive feature of NB-EP as a
monomer, it can be regarded as a useful precursor for vari-
ous norbornene monomers because of the diverse reactivity
of epoxide moiety that would allow a wide variety of its
chemical modifications. One of such chemical modifications
of epoxide that have been investigated by us so far is the
reaction with carbon dioxide at atmospheric pressure, which
can be efficiently catalyzed by alkali metal halides, such as
lithium bromide.15 This reaction is highly attractive not only
as an efficient chemical fixation of carbon dioxide but also as
a straightforward access to five-membered cyclic carbonates,
which are highly polar and highly electrophilic molecules
that accept selective nucleophilic attack of amines.16
The current growing interest in this field is the introduction
of various functional groups into the side chain of poly(nor-
bornene) for the purpose of giving or enhancing some spe-
cific chemical and physical properties, such as high process-
ing ability, adhesive strength, relief of birefringence, and
dielectric and optical properties. As described above, ROMP
is applicable to a wide range of monomers by virtue of its
compatibility with various functional groups. On the other
Herein, we report the reaction of the epoxy moiety of NB-EP
with carbon dioxide to afford the corresponding norbornene
Correspondence to: T. Endo (E-mail: tendo@mol-eng.fuk.kindai.ac.jp)
C
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monomer having five-membered cyclic carbonate moiety
(NB-CC) and its ROMP17 and palladium-catalyzed addition
polymerization to synthesize new poly(norbornene)s, of
which side chains were endowed with the reactivity of cyclic
carbonate (CC).
NMR (in CDCl3) d 139.24, 138.30, 137.70, 136.91, 135.94,
135.41, 132.43, 130.50, 81.98, 81.21, 80.46, 80.04, 69.44,
68.92, 68.85, 68.78, 49.61, 48.92, 45.37, 44.74, 44.01, 43.42,
43.37, 43.33, 43.31, 43.21, 43.02, 42.98, 42.13, 41.95, 41.81,
41.72, 29.26, 29.13, 27.74, 27.05 ppm; IR (neat) 2966(CAH,
stretching), 1785 (C¼¼O, stretching), 1160, 1053, 772, 716;
GC-MS (EI) m/z 180 (Mþ).
EXPERIMENTAL
Materials
ROMP of NB-CC
Benzylidene-bis(tricyclohexylphosphine)dichlororuthenium
(Grubbs first generation catalyst) (Aldrich), palladium ace-
tate (99.5%, Aldrich), and phenylcarbenium tetrakis(penta-
fluorophenyl)borate (Toso Finechem) were used as received.
Tricyclohexylphosphine (Aldrich) was washed by several
portions of MeOH and dried under vacuum at room tempera-
ture and flushed by N2 gas before use. NB-EP was synthe-
sized according to the procedure reported by us.14 5-Butyl-
2-norbornene was provided by JSR, and was purified before
use by passing through alumina column and distillation
under vacuum. Dichloromethane was distilled after refluxing
over calcium hydride. Toluene was distilled after refluxing
over sodium.
Homopolymerization
To a solution of NB-CC (360 mg, 2.00 mmol) in dichlorome-
thane (2.6 mL), a solution of Grubbs first generation catalyst
in dichloromethane (0.1 M; 0.2 mL, 0.02 mmol) was added
at room temperature. After 2 h, ethyl vinyl ether (0.25 mL)
was added to terminate the polymerization, and the mixture
was stirred at room temperature for 40 min. The mixture
was poured into methanol (50 mL), and the resulting precip-
itate was filtered with suction, and dried under vacuum to
obtain the homopolymer 1a (351 mg, 97%): IR (neat) 2931,
2867 (each CAH, stretching), 1788 (C¼¼O, stretching), 1167,
1063 (each CAO, stretching) cmꢂ1 1H NMR (DMSO-d6) d
;
5.50–5.05 (broad m, HAC¼¼CAH), 4.90–4.00 (broad m,
cyclic-carbonate-CH and ACH2), 3.20–0.90 ppm (broad m,
CH, and CH2 signals of main chain).
Measurements
Fourier transfer IR measurement was carried out at room
temperature by casting a sample solution on prism of ATR
measurement unit on a Perkin–Elmer spectrum-one spectro-
photometer. 1H NMR (400 MHz) and 13C NMR (100.6 MHz)
spectra were obtained with Varian NMR spectrometer, a
model Unit INOVA in CDCl3 with tetramethylsilane as an in-
ternal standard. Number- and weight average molecular
weights (Mn and Mw) were estimated by size exclusion chro-
matography (SEC), performed on a Tosoh chromatograph
model HLC-8120GPC equipped with Tosoh TSK gel-Super
HM-H styrogel columns (6.0 mm / ꢀ 15 cm), using CHCl3 as
an eluent at a flow rate of 1.0 mL/min after calibration with
polystyrene standards. Mass spectroscopy was performed on
a Shimadzu GCMS-QP5050A by EI mode. Gas chromatogra-
phy (GC) was performed on a Agilent Technologies 6850
Network GC system equipped with J and W Scientific HP-1
(0.25 mm ꢀ 30 m) capillary column and a Shimadzu GC-18A
GC equipped with J and W Scientific DB-WAXETR (1 mm ꢀ
30 m) capillary column, with using 1,2,3,4-tetrahydronaph-
thalene as a internal standard.
Copolymerization with BNB
NB-CC (180 mg, 1.00 mmol) and BNB (150 mg, 1.00 mmol)
were dissolved in dichloromethane (2.6 mL). To the obtained
solution, a solution of Grubbs first generation catalyst in
dichloromethane (0.1 M; 0.2 mL, 0.02 mmol) was added at
room temperature. After 2 h, ethyl vinyl ether (0.25 mL) was
added to terminate the polymerization, and the solution was
stirred at room temperature for 40 min. The solution was
poured into methanol (50 mL), and the resulting precipitate
was filtered with suction, and dried under vacuum to obtain
the comopolymer 1b (320 mg, 97%): IR (neat) 2952, 2925,
2868, 2856 (each CAH, stretching), 1801 (C¼¼O, stretching),
1
1169, 1067 (each CAO, stretching); H NMR (CDCl3) d 5.70–
5.00 (broad m, HAC¼¼CAH), 4.90–4.00 (broad m, cyclic-car-
bonate ACH and ACH2), 3.30–0.60 ppm (broad m, CH, and
CH2 signals of main chain and butyl group). Mn ¼ 20,000,
Mw ¼ 34,000 (estimated by SEC, eluent ¼ chloroform, poly-
styrene standards).
Palladium-catalyzed addition polymerization
of NB-CC and BNB
Synthesis of 4-Bicyclo[2.2.1]hept-50-en-20-yl
1,3-dioxolan-2-one (NB-CC)
To a toluene solution of palladium acetate (10 mM; 5 mL,
0.05 mmol), a toluene solution of tricyclohexylphosphine (10
mM; 5 mL, 0.05 mmol), and the solution was stirred for 30
min (¼ solution A; [Pd] ¼ 0.005 mM). In another vessel, a
toluene solution of phenylcarbenium tetrakis(pentafluoro-
phenyl)borate ([Ph3C][B(C6F5)4]) (2.0 mM; 10 mL, 0.020
mmol) was prepared ( ¼ solution B).
A solution of NB-EP (5.44 g, 39.9 mmol) and lithium bro-
mideꢁ (345 mg; 4.00 mmol) in 40 mL of NMP was stirred at
100 C for 11 h under CO2 atmosphere (1 atm). The result-
ing solution was poured into ice water (140 mL) and the
mixture was stirred for 10 min. To the mixture, dichlorome-
thane (120 mL) was added, and the organic layer was sepa-
rated, washed by distilled water twice, dried over MgSO4, fil-
trated, and concentrated under reduced pressure. The
residue was distilled in vacuo (0.1 mmHg, 121–123 ꢁC) to
obtain NB-CC (6.05 g, 33.6 mmol, 84% yield) as a colorless
liquid: 1H NMR (in CDCl3) d 6.30–5.83 (m, 2H, vinyl),
4.67–4.05 (m, 3H, AOACH2ACHAOA), 3.15–2.52 (m, 2H,
1-CH, 4-CH), 2.46–0.50 (m, 5H, 2-CH, 3-CH2, 7-CH2); 13C
To a solution of NB-CC (0.5 mmol) and BNB (225 mg, 1.5
mmol) in toluene (2.6 mL), solution A (0.4 mL; amount of
palladium ¼ 0.002 mmol) was added, then after 5 min, solu-
tion B (1.0 mL; amount of borate ¼ 0.002 mmol) was added.
ꢁ
The resulting solution was agitated at 25 C. After 56 h, the
solution was poured into methanol (50 mL) and the
SYNTHESIS OF A NORBORNENE MONOMER, SUDO, MORISHITA, AND ENDO
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JOURNAL OF POLYMER SCIENCE: PART A: POLYMER CHEMISTRY DOI 10.1002/POLA
resulting precipitate was filtered with suction, dried under
vacuum, to obtain the copolymer 2b (158.5 mg, 50%): IR
(neat) 2952, 2921, 2869, 2855 (each CAH, stretching), 1819
(C¼¼O, stretching), 1157, 1068 (each CAO, stretching); 1H
NMR (CDCl3) d 4.80–3.80 (broad d, cyclic-carbonate-CH and
ACH2), 3.00–0.40 ppm (broad m, CH and CH2 signals of
main chain and butyl group). Mn ¼ 61,000, Mw ¼ 195,000
(estimated by SEC, eluent
standards).
¼
chloroform, polystyrene
Aminolysis of the CC-moieties of 2b
To a solution of copolymer 2b (49.5 mg, amount of cyclic
carbonate moiety ¼ 0.33 mmol) in chlorobenzene (0.30 mL),
benzylamine (813 mg; 7.59 mmol) was added at ambient
ꢁ
temperature. The resulting solution was heated at 120 C for
36 h. During the reaction, small portions of the solution
were taken and analyzed by IR to determine the conversions
of the cyclic carbonate moiety. The solution was poured into
methanol (25 mL), and the resulting precipitate was filtered
with suction and dried under vacuum to obtain the resulting
polymer 3 (41.5 mg) as a white powder: IR (neat) 1715,
SCHEME 1 Synthesis of NB-CC.
1
1735 (C¼¼O, stretching); H NMR (CDCl3) d 4.3–4.5 (broad s,
CH2 of the benzyl protons), 4.9–5.1 ppm (broad s, NH). Mn ¼
39,000, Mw ¼ 96,000 (estimated by SEC, eluent ¼ chloro-
form, polystyrene standards).
For the determination of the conversions by IR, calibration
was performed by using two model compounds. One is NB-
CC that can simulate the cyclic carbonate structure in the
side chain, and the other is a urethane obtained by the sim-
ple reaction of butylisocyanate and ethanol. These model
compounds were mixed in several feed ratios, and the mix-
tures were analyzed by IR to obtain the relationship between
FIGURE 1 IR spectra of (a) NB-CC; (b) the homopolymer 1a
obtained by the ring-opening metathesis homopolymerization
of NB-CC; (c) the copolymer 1b obtained by the ring-opening
metathesis copolymerization of NB-CC and BNB (feed ratio ¼
50:50).
FIGURE 2 1H NMR spectra of (a) NB-CC; (b) the copolymer 1b
obtained by the ring-opening metathesis copolymerization of
NB-CC and BNB (feed ratio ¼ 50:50).
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TABLE 1 ROMP of NB-CC
[NB-CC]0:
feed ratio and peak area ratio, which was used for the quan-
titative analysis.
Yield
(%)a
Mn (Mw/Mn)b
m:nc
b
Entry
[BNB]0
Polymer
RESULTS AND DISCUSSION
1
2
a
100:0
50:50
1a
1b
97
97
NDd
100:0
50:50
Synthesis of NB-CC
11,000 (2.36)
Scheme 1 shows the synthetic route to NB-CC. The precursor
of NB-CC was synthesized from 5-norbornene-2-carbaldehyde
(a diastereomeric mixture of endo/exo) according to our pre-
vious report14: The aldehyde was reacted with S,S-dimethylth-
ioylide, prepared by treatment of trimethylsulfonium iodide
with potassium t-butoxide, to afford NB-EP in 81% yield. The
obtained NB-EP was dissolved in N-methylpyrrolidone
(NMP), and was heated in the presence of 10 mol % lithium
bromide under carbon dioxide gas (1 atm). As a result, the
epoxide moiety of NB-EP was converted successfully to the
corresponding five-membered cyclic carbonate moiety to
afford NB-CC. The carbonate structure was confirmed by its
strong IR-absorption at 1785 cmꢂ1 [Fig. 1(a)]. Figure 2(a)
shows the 1H NMR spectrum of the obtained NB-CC. The com-
plexity of the spectrum suggested that NB-CC was obtained as
a mixture of diastereomers. In fact, GC-MS analysis (ionized in
electron impact (EI) mode) of NB-CC revealed that it was a
mixture of four diasteromers, and this observation was in
good agreement with the sterochemical nature of NB-CC,
which has two chiral centers. All of the four diasteromers
detected by MS had a common m/z value of 180, which was
identical with the molecular weight of NB-CC.
MeOH-insoluble parts.
b
c
Estimated by SEC (eluent ¼ chloroform, pSt-standards).
Determined by 1H NMR.
d
Not determined because 1a was not soluble in chloroform.
ing homopolymer 1a almost quantitatively (Table 1, entry 1).
During the polymerization, 1a was precipitate out of the solu-
tion. 1a was not soluble in chloroform, acetone, and THF. In
more polar solvents, such as DMSO and DMF, 1a was appa-
rently soluble, but actually it was not: The apparent solutions
did not pass through a membrane filter, implying that 1a
aggregated to form microgel particles presumably because of
strong interaction between CC moieties. Figure 1(b) shows the
IR spectrum of the obtained homopolymer, which indicated a
strong absorption at 1788 cmꢂ1 attributable to the carbonate
moiety in the side chain. In addition to this successful homopo-
lymerization, the copolymerization of NB-CC and 5-butyl-2-
norbornene (BNB) in a feed ratio of 50:50 was achieved to
give the corresponding copolymer 1b (Table 1, entry 2). By the
incorporation of less polar n-butyl groups in the side chains,
1b gained its solubility in dichloromethane, chloroform, ace-
tone, and THF, which permitted its structural analysis by NMR
spectroscopy and estimation of its molecular weight by SEC.
1H NMR analysis of 1b clarified that the composition ratio was
50:50, which was same as the feed ratio [Fig. 2(b)].
ROMP of NB-CC
ROMP of NB-CC was performed with benzylidene-bis(tricyclo-
hexyl phosphine)dichlororuthenium (Grubbs first generation
catalyst) (Scheme 2), which was efficiently used in our previ-
ous work on ROMP of other types of norbornenes having car-
bonate moieties.17 When the catalyst was added to a dichloro-
methane solution of NB-CC, the ROMP proceeded smoothly to
consume NB-CC completely within 2 h, to give the correspond-
Palladium-Catalyzed Addition Polymerization of NB-CC
As a catalytic system for the addition polymerization of NB-
CC, a three component-system consisted of palladium (II) ac-
etate, tricyclohexylphosphine, and triphenylcarbenium tetra-
kis(pentafluorophenyl)borate was used (Scheme 3). Previ-
ously, we used this system to the copolymerization of NB-EP
and BNB in various feed ratio and obtained the
SCHEME 2 ROMP of NB-CC: Homopolymerization and copoly-
merization with BNB.
SCHEME 3 Palladium-catalyzed addition polymerization of NB-CC.
SYNTHESIS OF A NORBORNENE MONOMER, SUDO, MORISHITA, AND ENDO
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TABLE 2 Palladium-Catalyzed Addition Polymerization
of NB-CC
[NB-CC]0:
[BNB]0
Yield
(%)a
Mn (Mw/Mn)b
m:nc
b
Entry
Polymer
1
2
3
a
100:0
50:50
25:75
–
0
16
50
–
–
2a
2b
12 000 (3.7)
61 000 (3.2)
23:77
6:94
MeOH-insoluble parts.
b
c
Estimated by SEC (eluent ¼ chloroform, pSt-standards).
Determined by 1H NMR.
corresponding poly(norbornene)s having epoxy moiety in
the side chain.14
First, the homopolymerization of NB-CC was examined (Table
2, entry 1). To a toluene solution of NB-CC, the three compo-
nents of the catalyst system were added and the solution was
stirred at 25 ꢁC for 56 h. As a result, NB-CC was not consumed
and thus its homopolymer was not obtained at all. Previously,
we reported that the homopolymerization of NB-EP was much
slower than that of BNB, because of the strong interaction
between the ether oxygen of NB-EP and the cationic palladium
center of the catalyst, which hindered the coordination of the
CAC double bond of the norbornene moiety to the catalyst that
is inevitable for the addition polymerization.14 Analogously, the
unsuccessful homopolymerization of NB-CC is attributable to
the strong interaction between the cyclic carbonate (CC) moi-
ety and the palladium cationic center, which should be much
stronger than that between the epoxy moiety of NB-EP and the
catalyst, because CC is much more basic than epoxide.
FIGURE 3 IR spectra of the copolymers obtained by the addi-
tion copolymerization of NB-CC and BNB: (a) 2a (composition
ratio m:n ¼ 23:77); (b) 2b (composition ratio m:n ¼ 6:94). [Color
figure can be viewed in the online issue, which is available at
www.interscience.wiley.com.]
entry 3). As a result, the corresponding copolymer 2b was
obtained in a moderate yield. As shown in Figure 3(b), 2b
had a strong IR-absorption at 1819 cmꢂ1 to confirm the
Next, copolymerization of NB-CC and BNB in a feed ratio
of 50:50 was carried out with using the same catalytic system
(Table 2, entries 2). As a result, presumably by virtue of the
participation of the nonpolar BNB, the corresponding copoly-
mer 2a was obtained. Although the copolymerization was quite
slow to give only a small amount of the copolymer, the cyclic
carbonate moiety of the monomer was successfully introduced
into the side chain of the copolymer: Figure 3(a) shows the IR-
spectrum of the copolymer 2a, which clearly indicated a strong
absorption at 1816 cmꢂ1 because of the presence of five-mem-
bered cyclic carbonate (CC). The presence of CC was also con-
1
firmed by H NMR analysis [Fig. 4(a)]. The composition ratio
[NB-CC-derived unit]:[BNB-derived unit] of the copolymer
determined by its 1H NMR analysis was 23:77, that is, the con-
tent of NB-CC-derived unit was lower than that expected from
the feed ratio (¼ 50:50), to suggest that the polymerizability of
NB-CC was suppressed by the highly basic nature of CC moiety
that can bind to the cationic palladium. At the same time, BNB,
which can undergo the homopolymerization efficiently by
using the same catalyst system, was consumed quite slowly,
because of the occupation of the vacant site of the palladium
catalyst by the carbonate moiety.
FIGURE 4 1H NMR spectra of the copolymers obtained by the
addition copolymerization of NB-CC and BNB: (a) 2a (composi-
tion ratio m:n ¼ 23:77); (b) 2b (composition ratio m:n ¼ 6:94).
[Color figure can be viewed in the online issue, which is avail-
able at www.interscience.wiley.com.]
Copolymerization of NB-CC and BNB in a feed ratio of 25:75
was also examined, with expecting that the interference of
the polymerization by the strong coordination between CC
moiety and the cationic palladium could be diluted (Table 2,
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ARTICLE
FIGURE 5 Time-conversion relationships for the palladium-cat-
alyzed addition copolymerization of NB-CC and BNB (feed ratio
¼ 25:75).
SCHEME 4 Aminolysis of the cyclic carbonate moiety in the
side chain of the copolymer 2b.
and BNB was treated with an excess amount of benzylamine
presence of five-membered cyclic carbonate in the side
chain. By analyzing 1H NMR of 2b [Fig. 4(b)], the composi-
tion ratio [NB-CC-derived unit]:[BNB-derived unit] of 2c was
determined to be 6:93. This low content of NB-CC-derived
unit suggested that (1) the interaction between CC moiety
and the cationic palladium was reduced by the low initial
concentration of NB-CC to permit the improved efficiency of
the polymerization of BNB, but at the same time, (2) the low
initial concentration of NB-CC was disadvantageous in its
competition with BNB. Conversions of NB-CC and BNB in
the copolymerization were determined by GC, and the result-
ing time dependences of the conversions are shown in Fig-
ure 5, which clarified that (1) there was a significant differ-
ence in polymerizability between the two monomers and (2)
with depending on it, the two monomers underwent the sta-
tistic copolymerization to give the copolymer in which the
carbonate moieties would be distributed randomly.
([CC moiety]0:[benzylamine]0
¼
1:23) in chlorobenzene
(Scheme 4). The progress of the reaction was stꢁudied by 1H
NMR to find that it proceeded gradually at 120 C, resulting
in 83% conversion of CC after 36 h (Fig. 6). IR analysis of
the resulting polymer 3 confirmed the consumption of CC
and the corresponding formation of urethane linkage, of
which absorption was observed at around 1740 cmꢂ1 (Fig. 7).
The molecular weight of 3 estimated by SEC was smaller than
that of the precursor polymer 2b: as it is rather difficult to
postulate scission of the poly(norbornene) main chain under
Reaction of the Cyclic Carbonate Moiety in the
Side Chain with Amine
We have reported the reaction of five-membered cyclic car-
bonate with amines, which affords the corresponding ure-
thanes having hydroxyl group15,16: The characteristic feature
of this reaction is its chemoselectivity, which permits the
nucleophilic addition of primary amine exclusively in the
presence of other nucleophiles, such as secondary amine, alco-
hol, and carboxylic acid. This chemoselectivity has allowed us
to design and synthesize various polyurethanes having func-
tional groups, which can not be achieved by the conventional
polyaddition reaction with using diisocyanates and diols.
To investigate the reactivity of the cyclic moiety in the side
chain of poly(norbornene), the copolymer 2b obtained by
the palladium-catalyzed addition copolymerization of NB-CC
FIGURE 6 Time-dependence of conversion of the cyclic carbon-
ate moiety of 2b in its reaction with benzylamine.
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FIGURE 7 IR spectra of (a) the copolymer 2b and (b) the polymer
3 obtained by the reaction of the cyclic carbonate moiety of 2b
with benzylamine. [Color figure can be viewed in the online
issue, which is available at www.interscience.wiley.com.]
the conditions, the relatively smaller molecular weight of 3
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thane and hydroxyl groups.18
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SUMMARY
9 Hasan, T.; Ikeda, T.; Shiono, T. Macromolecules 2004, 37,
7432–7436.
A new functionalized norbornene monomer having five-mem-
bered cyclic carbonate moiety (¼ NB-CC) was synthesized
based on the efficient fixation of carbon dioxide (1 atm) as a
carbonyl source. NB-CC and 5-butyl-2-norbornene were copo-
lymerized by the methods of ROMP and palladium-catalyzed
addition polymerization to afford the corresponding poly(nor-
bornene)s having cyclic carbonate pendants, which are reac-
tive with amine to permit potential utilization of the polymers
as scaffolds for polymer architectures involving networked
poly(norbornene)s. Further investigation on exploiting other
catalyst systems to make the best use of this new monomer
for well-defined synthesis of cyclic carbonate-functionalized
poly(norbornene)s will be continued.
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17 Previously, we reported ROMP of analogous norbornenes
having cyclic carbonate moieties: Hino, T.; Inoue, N.; Endo, T.
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18 For a similar phenomenon, see: Sudo, A.; Kudoh, R.;
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