Synthesis of high-Tg polymers via ROMP of oxanorbornene dicarboximides with halogen groups

Article abstract of DOI:10.1002/hc.20576

This paper describes the synthesis of exo-N-phenyl-7-oxanorbornene-5, 6-dicarboximides with different substituents at para positions in the aromatic ring and their polymerization by ring-opening metathesis polymerization (ROMP) leading to high-T_g polymers. Exo-N-4-chlorophenyl-7- oxanorbornene-5, 6-dicarboximide (ClPhONDI, 3a), exo-N-4-bromophenyl-7-oxanorbornene-5, 6-dicarboximide (BrPhONDI, 3b), and exo-N-4-iodophenyl- 7-oxanorbornene-5, 6-dicarboximide (IPhONDI, 3c) monomers were synthesized. Polynorbornene dicarboximides were obtained via ROMP using a first-generation ruthenium alkylidene catalyst, Cl₂(PCy₃)₂Ru(=CHPh). The resulting amorphous polymers with trans configuration of the double bonds were characterized by NMR, SEM, DSC, and GPC.

Full text of DOI:10.1002/hc.20576

Heteroatom Chemistry
Volume 21, Number 1, 2010
Synthesis of High-T Polymers via ROMP of
g
Oxanorbornene Dicarboximides with Halogen
Groups
Sevil C¸ etinkaya and Rifat Bayram
Department of Chemistry, Kirikkale University, 71450 Yahsihan, Kirikkale, Turkey
Received 16 October 2009; revised 13 January 2010
sis and their application to the synthesis of well-
ABSTRACT: This paper describes the synthesis of
defined products [1]. Especially, the discovery of
exo-N-phenyl-7-oxanorbornene-5, 6-dicarboximides
ruthenium alkylidene complexes has had a profound
with different substituents at para positions in
impact on this field since they permit the polymeriza-
the aromatic ring and their polymerization by
tion of highly functionalized and sterically hindered
ring-opening metathesis polymerization (ROMP)
monomers [2]. Functionalized norbornenes easily
leading to high-Tg polymers. Exo-N-4-chlorophenyl-7-
participate in ring-opening metathesis polymeriza-
oxanorbornene-5,6-dicarboximide (ClPhONDI, 3a),
tion (ROMP) with approximate complete conversion
exo-N-4-bromophenyl-7-oxanorbornene-5,6-dicarbo-
to high molecular weight polymers with good me-
ximide (BrPhONDI, 3b), and exo-N-4-iodophenyl-
chanical properties [3,4]. ROMP of 7-oxanorbornene
7-oxanorbornene-5,6-dicarboximide
3c) monomers were synthesized. Polynorbornene
dicarboximides were obtained via ROMP using
(IPhONDI,
dicarboximides with linear aliphatic and phenyl
substituents using appropriate catalysts has been
reported [5,6]. The carboximide-functionalized
polynorbornenes show high heat resistance, low
moisture absorption, good mechanical, and thermo-
plastic properties. They have high glass transition
temperatures (Tg) greater than about 150◦C [4,7–11].
The membranes prepared from polyoxanorbornenes
with lateral imide groups exhibit high permselectiv-
ity for the separation of hydrogen from nitrogen,
carbon monoxide, methane, and ethylene [12–14].
The ROMP of N-fluorophenyl-7-oxanorbornene-
a
first-generation ruthenium alkylidene catalyst,
Cl2(PCy3)2Ru( CHPh). The resulting amorphous
polymers with trans configuration of the double
bonds were characterized by NMR, SEM, DSC, and
ꢀ
C
GPC.
2010 Wiley Periodicals, Inc. Heteroatom Chem
21:36–43, 2010; Published online in Wiley InterScience
(www.interscience.wiley.com). DOI 10.1002/hc.20576
5,6-dicarboximides
has
been
studied
by
INTRODUCTION
Tlenkopatchev et al. [15]. To our knowledge,
the ROMP of 7-oxanorbornene dicarboximides
substituted with halogen (Cl, Br, I) has not been
reported using Grubbs-typed ruthenium alkylidene
catalysts until now. In this study, we aimed at
the preparation of new types of thermoplastic
materials. New unsaturated ROMP polymers having
high glass transition temperatures were obtained
via ring-opening metathesis polymerization with
ruthenium-based transition metal complex. The
norbornene monomers and the corresponding
ROMP polymers were fully characterized by NMR
Materials ranging in properties from soft rubber
to hard thermoplastics and cross-linked thermosets
can be prepared by metathesis chemistry. The de-
velopment of highly active metal-alkylidene cata-
lysts opens vast opportunities in olefin metathe-
Correspondence to: Sevil C¸ etinkaya; e-mail: scetinkaya@kku.
edu.tr
Contract grant sponsor: Kirikkale University Research Fund.
Contract grant number: BAP 2007/56.
2010 Wiley Periodicals, Inc.
c
ꢀ
36

Synthesis of High-Tg Polymers via ROMP of Oxanorbornene Dicarboximides with Halogen Groups 37
1H NMR (400 MHz, CDCl3): δ = 7.43–7.21
spectroscopy. The surface properties of ROMP poly-
mers were investigated by SEM (scanning electron
microscopy). In addition, the ROMP polymers were
characterized by GPC and DSC.
(4H, m), 6.57 (2H, s), 5.39 (2H, s), 3.01 (2H, s).
Synthesis of BrPhONDI (3b). A mixture
containing
10
mmol
exo-7-oxanorbornene-
5,6-dicarboxylic anhydride and 10 mmol 4-
bromoaniline in 30 mL acetone was stirred at room
temperature for about 1 h. Then 0.1 g Mn(Ac)2,
7 mL Et3N, and 60 mL (AcO)2O were added and the
mixture was heated to 50–60◦C for about 2 h, during
which solvent again became clear. The solution
was then cooled, insoluble solids were filtered,
and the filtrate was poured into 50 mL ice water.
The precipitated solid was collected by filtration
and recrystallized from methanol to give exo-N-4-
bromophenyl-7-oxanorbornene-5, 6-dicarboximide
(BrPhONDI, 3b). Yield: 92%.
EXPERIMENTAL DETAILS
Reagents
4-Bromoaniline, 4-chloroaniline, 4-iodoaniline,
furan, and maleic anhydride were purchased
from Sigma-Aldrich Chemical Co. (Taufkirchen,
Germany) and were used without further purifica-
tion. Dichloromethane was dried over anhydrous
calcium chloride and was distilled under nitrogen
over CaH2. Grubbs first generation catalyst, bis(tri-
cyclohexylphosphine)benzylidine
chloride, was purchased from Sigma-Aldrich
Chemical Co. and was used as received.
ruthenium(IV)
1H NMR (400 MHz, CDCl3): δ = 7.62–7.20
(4H, m), 6.59 (2H, s), 5.41 (2H, s), 3.03 (2H, s).
Synthesis of IPhONDI (3c). A mixture contain-
ing 10 mmol exo-7-oxanorbornene-5,6-dicarboxylic
anhydride and 10 mmol 4-iodoaniline in 30 mL ace-
tone was stirred at room temperature for about
1 h. Then 0.1 g Mn(Ac)2, 7 mL Et3N, and 60 mL
(AcO)2O were added and the mixture was heated
to 50–60◦C for about 2 h, during which sol-
vent again became clear. The solution was then
cooled, insoluble solids were filtered, and the filtrate
was poured into 50 mL ice water. The precipi-
tated solid was collected by filtration and recrys-
tallized from methanol to give exo-N-4-iodophenyl-
7-oxanorbornene-5,6-dicarboximide (IPhONDI, 3c).
Yield: 61%.
Techniques
1H NMR and 13C NMR spectra were recorded on
a Bruker Avance DPX spectrometer at 400 MHz
in CDCl3 or DMSO. Tetramethylsilane (TMS) was
used as an internal standard. Glass transition tem-
peratures were determined in a Perkin Elmer Di-
amond DSC instrument at a scanning rate of
−1
10◦C min under nitrogen atmosphere. Each sam-
ple was run twice in the temperature range between
20 and 280◦C under nitrogen atmosphere. Molecular
weights and molecular weight distributions were de-
termined with reference to polystyrene standards on
an Agilent (HP) GPC at 30◦C, in THF for polymers
and a flow rate of 1 mL min −1. SEM photographs
were taken with JOL JSB 5600.
1H NMR (400 MHz, CDCl3): δ = 7.83–7.06
(4H, m), 6.59 (2H, s), 5.41 (2H, s), 3.03 (2H, s).
Synthesis and Characterization of Monomers
Metathesis Polymerization of Monomers
Synthesis
of
ClPhONDI
(3a). Exo-7-
Polymerizations were carried out in Schlenk tubes
under nitrogen atmosphere at room temperature.
Polymers were synthesized using a monomer to
a catalyst ratio of 200:1. The obtained polymers,
4a, 4b, 4c, were soluble in dimethyl formamide,
dimethyl sulfoxide, and dichloromethane.
oxanorbornene-5,6-dicarboxylic anhydride was
prepared as described in the literature [16]. A mix-
ture containing 10 mmol exo-7-oxanorbornene-5,6-
dicarboxylic anhydride and 10 mmol 4-chloroaniline
in 30 mL acetone was stirred at room temperature
for about 1 h. Then 0.1 g Mn(Ac)2, 7 mL Et3N,
and 60 mL (AcO)2O were added and the mixture
was heated to 50–60◦C for about 2 h, during which
solvent again became clear. The solution was then
cooled, insoluble solids were filtered, and the filtrate
was poured into 50 mL ice water. The precipitated
solid was collected by filtration and recrystallized
from methanol to give exo-N-4-chlorophenyl-7-
oxanorbornene-5,6-dicarboximide (ClPhONDI, 3a).
Yield: 67%.
Synthesis of PClPhONDI (4a). The solution
of 28.35 mg of ruthenium initiator in 1.0 mL
of CH2Cl2in a glass vial was added to the solution of
the estimated amount of 3a in 1 mL CH2Cl2.
The mixture was left stirring for 24 h. The living
propagation species were quenched with 3–5 drops
of ethyl vinyl ether for 30 min stirring. The polymer
was precipitated in cold hexane (10 times of the
volume of solution), was dissolved again in CH2Cl2,
Heteroatom Chemistry DOI 10.1002/hc

38 C¸etinkaya and Bayram
1H NMR (400 MHz, DMSO): δ = 7.66–7.21
(4H, m), 6.02 (2H, s, trans), 5.78 (2H, s, cis), 5.08
(2H, s), 4.61 (2H, s), 3.60 (2H, s).
and was reprecipitated from hexane. The ob-
tained product, poly (exo-N-4-chlorophenyl-7-
oxanorbornene-5,6-dicarboximide
(PClPhONDI,
13C NMR (400 MHz, DMSO): δ = 175.1, 132.3,
131.8, 131.5, 129.7, 122.0, 80.2, 76.6, 52.9.
4a), was dried under vacuum.
1H NMR (400 MHz, DMSO): δ = 7.58–7.20
(4H, m), 6.04 (2H, s, trans), 5.82 (2H, s, cis), 5.08
(2H, s), 4.67 (2H, s), 3.53 (2H, s).
13C NMR (400 MHz, DMSO): δ = 175.1, 133.4,
131.3, 129.5, 129.0, 80.1, 76.6, 52.8.
RESULTS AND DISCUSSION
N-Phenyl-oxanorbornene-5,6-dicarboximides with
substituents (chloro, bromo, and iodo) were inves-
tigated for polymerization. All monomers used in
the polymerizations were of exo stereochemistry. We
have carried out [4 + 2] cycloaddition of furan with
maleic anhydride to obtain exo-7-oxanorbornene-
5,6-dicarboxylic anhydride (1), as described in
the literature [16]. Then p-halo-substituted ani-
lines were reacted with exo-7-oxanorbornene-5,6-
dicarboxylic anhydride to the corresponding prod-
ucts, which were cyclized to exo-imides using acetic
anhydride as dehydrating agent (Scheme 1). Exo
monomers, 3a, 3b, and 3c, were synthesized by
Diels–Alder reactions with good yields (61%–92%).
1H NMR confirmed monomer structures and purity.
The monomer olefinic signals were seen at 6.57–
6.59 ppm. The signals for hydrogen in the phenyl
ring shifted ppm further depending on the size of
Synthesis of PBrPhONDI (4b). The solution of
28.35 mg of ruthenium initiator in 1.0 mL of
CH2Cl2in a glass vial was added to the solution
of the estimated amount of 3b in 1 mL CH2Cl2.
The mixture was left stirring for 24 h. The living
propagation species were quenched with 3–5 drops
of ethyl vinyl ether for 30 min stirring. The poly-
mer was precipitated in cold hexane (10 times of
the volume of solution), dissolved again in CH2Cl2,
and reprecipitated from hexane. The obtained prod-
uct, poly (exo-N-4-bromophenyl-7-oxanorbornene-
5,6-dicarboximide (PBrPhONDI, 4b), was dried un-
der vacuum.
1H NMR (400 MHz, DMSO): δ = 7.68–7.18
(4H, m), 6.04 (2H, s, trans), 5.80 (2H, s, cis), 5.08
(2H, s), 4.60 (2H, s), 3.54 (2H, s).
13C NMR (400 MHz, DMSO): δ = 175.5, 131.3,
131.1, 129.8, 121.9, 80.1, 76.6, 52.8.
1
the substituted group. The H NMR spectra of 3a,
3b, and 3c had phenyl proton signals at 7.21–7.43,
7.20–7.62, and 7.06–7.83 ppm, respectively.
Synthesis of PIPhONDI (4c). The solution
of 28.35 mg of ruthenium initiator in 1.0 mL
of CH2Cl2in a glass vial was added to the solu-
tion of the estimated amount 3c in 1 mL CH2Cl2.
The mixture was left stirring for 24 h. The living
propagation species were quenched with 3–5 drops
of ethyl vinyl ether for 30 min stirring. The poly-
mer was precipitated in cold hexane (10 times of
the volume of solution), dissolved again in CH2Cl2,
and reprecipitated from hexane. The obtained prod-
uct, poly (exo-N-4-iodophenyl-7-oxanorbornene-5,6-
dicarboximide) PIPhONDI, 4c), was dried under
vacuum.
Ring-opening metathesis polymerization reac-
tions of exo monomers using first generation ruthe-
nium alkylidene catalyst, bis(tricyclohexylphos-
phine)benzylidine ruthenium(IV) chloride, were
carried out in dichloromethane at room tempera-
ture (Scheme 2), and the corresponding polymers
were obtained with high yields (68%–88%).
After removal of the residual monomers, the
polymers were characterized for the microstructure
by NMR and the molecular weight and molecu-
lar weight distribution by GPC. The experimental
molecular weights are in agreement with the the-
oretical ones. Molecular weight of polymers can
O
O
O
O
Et3N, (AcO)2O
Mn(OAc)2
N
R
+
R
O
NH2
O
O
1
2
3a–3c
2a R=Cl; 2b R=Br; 2c; R=I
3a R=Cl; 3b R=Br; 3c; R=I
SCHEME 1 Synthesis of monomers 3a, 3b, and 3c.
Heteroatom Chemistry DOI 10.1002/hc

Synthesis of High-Tg Polymers via ROMP of Oxanorbornene Dicarboximides with Halogen Groups 39
O
n
O
O
Ru(=CHPh)(PCy3)2Cl2
N
R
n
O
O
N
CH2Cl2
O
R
3a–3c
4a–4c
4a R=Cl; 4b R:Br; 4c; R=I
SCHEME 2 Ring-opening metathesis polymerization of monomers 3a, 3b, and 3c.
be controlled by the initial monomer to a catalyst
ratio. Changing the size of the substituted groups
on the phenyl rings did not affect the conversion
of monomers, molecular weight, and stereochem-
istry of the double bonds in the polymer. Table 1
summarizes the polymer characterization data for
4(a–c). Trans content in the polymers was deter-
mined by 1H NMR (from 1H NMR analysis of olefinic
protons). Ruthenium-based catalyst gave polymers
with trans configuration of the double bonds (58%–
74%). The results obtained by the GPC analysis show
that the molecular weights (Mw) are between 45,300
and 63,000.
polymer. Three major resonances, arising from
carbonyl (175.1 ppm), aromatic/olefinic (133.4–
129.0 ppm), and aliphatic (80.1–52.8 ppm) carbons
are detected in 13C NMR spectrum of PClPhONDI. As
shown in Table 1, the molecular weight and polydis-
persity of the polymer 4a are about 63,000 and 2.8,
respectively. PClPhONDI (4a) exhibits only one tran-
sition between 25◦C and 280◦C (Fig. 2). This transi-
tion at 183◦C is the glass transition temperature with
no detectable melting transition. This DSC result re-
veals that the polymer is completely amorphous.
When BrPhONDI (3b) was polymerized, a pre-
cipitate in the early minutes of the reaction was
observed resulting in a broader molecular weight
distribution, in comparison with polymers 4a
and 4c (Table 1). 1H NMR was used to de-
termine the cis/trans content in the polymer.
(PCy3)2(Cl)2Ru CHPh catalyst gave polymer with a
mixture of cis and trans double bonds, 59% of trans
structure. It is well known that many ruthenium-
based catalysts provide predominantly trans double
bonds in ROMP of other norbornenes [8,17].
Figure 1 shows the 1H NMR spectra of monomer
3a (a) and polymer 4a (b) prepared by ruthenium-
based catalyst,(PCy3)2(Cl)2Ru CHPh. The monomer
vinylic signals at 6.57 ppm are replaced by new sig-
nals. Polymer gives two signals in the vinylic re-
gion, one at 5.82 ppm and the other at 6.04 ppm.
By measurement of the J coupling, the signal at
6.04 ppm was associated with the trans proton, and
the signal at 5.82 ppm, with the cis proton. Based
on the intensities of these signals, PClPhONDI (4a)
is assigned to have a higher amount of trans con-
figuration. The peaks at 7.58–7.20 ppm correspond
to aromatic protons. The 13C NMR spectrum of
PClPhONDI agrees with the structure of the obtained
1
Figure 3 shows the H NMR spectra of monomer
3b (a) and polymer 4b (b). The monomer olefinic
signal at 6.59 ppm is replaced by new signals at 6.04
and 5.80 ppm, which correspond to the trans and cis
double bonds of the polymer, respectively. A clear
TABLE 1 ROMP of 3a, 3b, and 3c by (PCy3)2(Cl)2Ru CHPh Catalyst
Monomera
Polymerb
Yield (%)
Transc (%)
Mwd × 104
DPId
Tg(◦C)
3a
3b
3c
PClPhONDI
PBrPhONDI
PIPhONDI
88
68
72
74
59
58
6.30
4.53
5.12
2.8
4.8
2.2
183
193
227
aDichloromethane as the solvent, room temperature.
bMolar ratio of monomer to catalyst, 200/1.
cDetermined by 1H NMR.
dAccording to GPC analysis in THF with polystyrene calibration standards.
Heteroatom Chemistry DOI 10.1002/hc

40 C¸etinkaya and Bayram
FIGURE 1 1H NMR spectra of (a) monomer 3a and (b) polymer 4a prepared by (PCy3)2(Cl)2Ru CHPh.
effect of the size of the substituent on the Tg was ob-
served. The Tg increased with the increase in the van
der Waals radius of the parasubstituent. The Tg of
PBrPhONDI (4b) was observed at 193◦C (Fig. 4). The
hindered rotation of the phenyl group became higher
by the introduction of bromine atoms in the moiety
that raised the Tg of PBrPhONDI (4b) (Tg, 193◦C) in
comparison with polymer 4a (Tg, 183◦C). PIPhONDI
(4c) exhibits the higher glass transition temperature
of all the polymers studied here (Tg, 227◦C; Fig. 5).
This effect can be explained by the fact that bigger
size of the substituent on phenyl groups decreases
the segmental motion of the polymer backbone and
leads to higher Tgs.
PIPhONDI with molecular weight 51,200 was
1
obtained with polydispersity of 2.2. The H NMR
of IPhONDI (3c) and its polymer (4c) are shown in
Fig. 6. The polymerization was complete as indicated
FIGURE 2 DSC thermogram of PClPhONDI.
Heteroatom Chemistry DOI 10.1002/hc

Synthesis of High-Tg Polymers via ROMP of Oxanorbornene Dicarboximides with Halogen Groups 41
FIGURE 3 1H NMR spectra of (a) monomer 3b and (b) polymer 4b prepared by (PCy3)2(Cl)2Ru CHPh.
FIGURE 4 DSC thermogram of PBrPhONDI.
Heteroatom Chemistry DOI 10.1002/hc

42 C¸etinkaya and Bayram
FIGURE 5 DSC thermogram of PIPhONDI.
by the disappearance of the signal at 6.59 ppm and
the emergence of the trans-and cis-olefinic proton
resonances at 6.02 and 5.78 ppm, respectively. Para-
substitution with halogen (Cl to I) caused increas-
ing separation of aromatic hydrogens with bulki-
ness. The 13C NMR spectrum of 4c gives olefinic and
aromatic carbon signals of polymer chain at 132.3–
122.0 ppm. Carbonyl carbon and aliphatic carbon
FIGURE 6 1H NMR spectra of (a) monomer 3c and (b) polymer 4c prepared by (PCy3)2(Cl)2Ru CHPh.
Heteroatom Chemistry DOI 10.1002/hc

Synthesis of High-Tg Polymers via ROMP of Oxanorbornene Dicarboximides with Halogen Groups 43
opening metathesis polymerization of all monomers
gives an amorphous, rough surface, and similar mor-
phologies.
CONCLUSION
Exo-isomers of N-4-halo-substituted phenyl-7-
oxanorbornene-5,6-dicarboximides, ClPhONDI, Br-
PhONDI, and IPhONDI, were synthesized and poly-
merized via ROMP using the well-defined ruthenium
catalyst, (PCy3)2(Cl)2Ru CHPh. This catalyst pro-
duced amorphous polymers with trans configuration
of the double bonds. Glass transition temperatures
of the polymers changed with size of the substituted
groups on the phenyl ring.
ACKNOWLEDGEMENTS
We thank the Kirikkale University Foundation for
their support of this work.
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Heteroatom Chemistry DOI 10.1002/hc