High Tg sulfonated insertion polynorbornene ionomers prepared by catalytic insertion polymerization

Article abstract of DOI:10.1016/j.polymer.2016.01.047

A simple method to synthesize high Tg sulfonated ionomers based on catalytic insertion polynorbornene is reported. Copolymers of norbornene and 5-methyl alcohol norbornene (endo:exo = 82:18) or 5-methyl bromide norbornene (endo:exo = 86:14) as well as terpolymers of norbornene, 5-methyl alcohol norbornene and 5-hexyl norbornene are prepared using a cationic Pd catalyst. These copolymers are then thioacetylated. Using hydrogen peroxide as oxidant, a sulfonated polynorbornene is obtained. Ionomers containing as much as 30 mol% SO₃H and with Tgs above 200 °C are obtained in a four-step procedure of overall 40-75% yield.

Full text of DOI:10.1016/j.polymer.2016.01.047

Accepted Manuscript
High Tg sulfonated insertion polynorbornene ionomers prepared by catalytic insertion
polymerization
Florian Pierre, Basile Commarieu, Ana C. Tavares, Jerome Claverie
PII:
S0032-3861(16)30047-7
10.1016/j.polymer.2016.01.047
JPOL 18399
DOI:
Reference:
To appear in: Polymer
Received Date: 6 November 2015
Revised Date: 20 January 2016
Accepted Date: 20 January 2016
Please cite this article as: Pierre F, Commarieu B, Tavares AC, Claverie J, High Tg sulfonated insertion
polynorbornene ionomers prepared by catalytic insertion polymerization, Polymer (2016), doi: 10.1016/
j.polymer.2016.01.047.
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ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
High Tg Sulfonated Insertion Polynorbornene Ionomers Prepared by
Catalytic Insertion Polymerization
Florian Pierre1, Basile Commarieu1, Ana C. Tavares2, Jerome Claverie1*
1. NanoQAM, Québec Center for Functional Materials, UQAM, Dept de Chimie,
Succ Centre-Ville, CP8888 Montreal, H3C3P8 Qc, Canada
2. Québec Center for Functional Materials, Institut National de la Recherche
Scientifique – Énergie, Matériaux et Télécommunications, 1650 Boulevard Lionel-
Boulet, Varennes, Québec, Canada, J3X 1S2
ABSTRACT
A simple method to synthesize high Tg sulfonated ionomers based on catalytic
insertion polynorbornene is reported. Copolymers of norbornene and 5-methyl
alcohol norbornene (endo:exo = 82:18) or 5-methyl bromide norbornene (endo:exo
= 86:14) as well as terpolymers of norbornene, 5-methyl alcohol norbornene and 5-
hexyl norbornene are prepared using a cationic Pd catalyst. These copolymers are
then thioacetylated. Using hydrogen peroxide as oxidant,
a
sulfonated
polynorbornene is obtained. Ionomers containing as much as 30 mol% SO3H and
with Tgs above 200 oC are obtained in a four-step procedure of overall 40-75% yield.

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1. INTRODUCTION
Currently, Nafion is the state-of-the-art commercial proton exchange membrane
(PEM) used in fuel cell devices [1]. Its high ionic conductivity, good chemical and
mechanical stability even when swollen by water makes it an excellent candidate for
such an usage. Protons can diffuse through hydrated channels which originate from a
microphase separation between the hydrophobic polytetrafluoroethylene backbone
and polar domains containing the sulfonic acid moieties [2]. However, at
temperatures higher than 100 °C, Nafion loses its mechanical strength when well
hydrated [3]. In order to address this issue, several high Tg sulfonated polymers such
as polyetherketones, polyimides, polybenzimidazoles, polyarylether and
polyphosphazenes have been scrutinized [1,4-7]. Polymers based on vinyl monomers
have also been studied such as grafted sodium poly(styrene sulfonate) chains on
polyethylene [8,9], on poly(ethylene-co-tetrafluoroethylene) [10] or polyvinylidene
fluoride [11]. Nonetheless, currently no polymer completely fulfills the stringent set
of conditions (conductivity, stability, durability, cost, etc…) required for functional
sulfonated PEMs operating at temperatures above 100 oC. Thus, the search for novel
high Tg sulfonated ionomers is the object of intense research [1,4].
Recently, it has been demonstrated that insertion polynorbornenes (PNBE) could
successfully be used for the preparation of PEMs [12–16]. This polymer is
particularly promising as it exhibits a glass-transition temperature (Tg) around 350-
400 °C and an excellent chemical stability stemming from its saturated backbone
[17]. Such PNBE is obtained by the insertion polymerization of norbornene (NBE)
and its properties are vastly different from the PNBE obtained by ring-opening
metathesis polymerization. Wang et al [14] cross-linked insertion PNBE with 4,5-
imidazole dicarboxylic acid (IDA) and doped it with phosphoric acid. The resulting
membranes were stable up to 280 °C and their conductivities reached 3.05 mS.cm-1 at

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80 °C. He et al [13], prepared an anion exchange membrane based on PNBE, with
conductivity as high as 4.14 mS.cm-1 at 80 °C. Daigle et al. [12] prepared proton
exchange membranes based on a terpolymer of ethylene, norbornene and norbornene-
5-exo-methyl sulfonic acid, using exo monomers only (as endo monomers are usually
not reactive [18]). The resulting PEM exhibits a moderate conductivity at 100 °C.
Although it appears that the PNBE backbone can be exploited for the design of
ionomers as fuel cell membranes, the preparation of these ionomers remains
challenging and time-consuming. Recently, we demonstrated that the sulfonic moiety
could readily be introduced by oxidation of the thioacetate moiety with H2O2, thus
precluding the need of corrosive chlorosulfonic acid as sulfonation agent [12].
However, the preparation of insertion PNBE bearing pendant thioacetate groups, and
more generally the preparation of any PNBE bearing pendant polar groups, is
complicated by the fact that only a low number of catalysts are able to insert polar
norbornenes [19,20]. Furthermore, substituted NBEs containing heteroatoms in endo
conformation can actually significantly retard or even stop the polymerization
[18,19]. Under standard laboratory conditions, the Diels-Alder reaction usually forms
a polar norbornene monomer containing more than 50% endo isomer. The endo
isomer must be separated from the exo one prior polymerization if a high
polymerization yield is targeted. Recently, we have demonstrated that the lack of
reactivity of the endo monomer can be bypassed via the rectification-insertion
mechanism, whereby the catalyst not only promotes the monomer insertion, but also
catalyzes the isomerization of the endo monomer into exo monomer. We here
demonstrate that the rectification-insertion mechanism can be used for the
polymerization of norbornene-5-methyl bromide (NBE-CH2Br) and norbornene-5-
methyl alcohol (NBE-CH2OH) and its copolymerization with norbornene and alkyl
norbornenes. Remarkably, as none of the endo and exo isomers are separated, this
synthetic scheme (Scheme 1) represents a very simple route toward the synthesis of
PNBE-based sulfonated ionomers. In this study, our goal is to prepare ionomers
based on insertion PNBE, in order to benefit from the very high Tg and chemical

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robustness of this polymer. In order to introduce proton conducting moieties, a
substituted norbornene (NBE-CH2OH or NBE-CH2Br) is copolymerized and then
converted to sulfonic group (Scheme 1). Furtermore, to improve the processability of
the resulting copolymer, a third monomer, 5-hexyl-norbornene (NBE-Hxl) is also
copolymerized. Thus terpolymers of NBE, NBE-Hxl and a norbornene unit
containing a pendant SO3H were prepared and were shown to be interesting
candidates for preparing PEM.
[PdCl(C3H5)]2,
AgSbF6
y
y
x
x
(a)
OH
+
NBE-CH2OH
NBE
OH
OMs
(b)
[PdCl(C3H5)]2,
AgSbF6
y
x
y
(b)
(c)
x
y
x
Br
+
NBE-CH2Br
Br
S
SO3H
O
Scheme 1. Preparation of the sulfonated PNBE (a) Toluene, THF (both anhydrous),
Mesyl Chloride, Et3N, reflux, 6 h. (b) Toluene, DMF (both anhydrous), Potassium
thioacetate, reflux 12 h. (c) H2O2 30% w/w in H2O, AcOH, iPrOH, 65 oC, 12 h.
2. EXPERIMENTAL
2.1 Materials and general considerations
All the manipulations that involved air and/or moisture sensitive compounds were
performed using a nitrogen filled glove-box. All chemicals were purchased from

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Sigma-Aldrich and were stored under nitrogen. Allyl alcohol, allyl bromide and 1-
octene were distilled prior utilisation in Diels-Alder reactions. Liquid monomers used
for polymerization reactions were dried over molecular sieves and deoxygenated by
bubbling the liquids with nitrogen prior insertion into the glove-box. Solvents used
for the mesylation and thioacetylation reactions such as THF, DMF and Toluene were
obtained from a solvent purification system from mBraun.
2.2 Instrumentation
1H, 13C NMR spectra were recorded on a Bruker Ultrashield 300 MHz at ambient
1
temperature and H chemical shifts were referenced to the solvent signal. The solid
polymers FTIR spectra were recorded on a Nicolet 6700 Spectrometer equipped with
Smart ATR accessory. The molecular weights of the polymers were determined by
gel permeation chromatography (GPC) using a Viscotek HT GPC instrument
equipped with three columns, 2 PLGel 10 µm Mixed B LS and 1 Agilent PLGel 20
µm Mixed ALS and running in THF at 40 oC. Glass transition temperatures (Tg) were
measured by differential scanning calorimetry (DSC) using a DSC1 Mettler Toledo
o
device using a 10 C/min heating and cooling scan. The second heating ramp was
used to determine Tg.
2.3 Synthesis of norbornene-5-methyl alcohol NBE-CH2OH
The synthesis of the different monomers used was performed in a Parr pressurized
reactor (300 mL) as pressures ranging from 100 to 200 psi were attained depending
on the reaction temperature. Dicyclopentadiene (DCPD) (100 g, 0.76 mol, 1.0 eq) and
allyl alcohol (62 g, 1.06 mol, and 1.4 eq) were added to the reaction vessel and the
mixture was heated at 210 °C for 2 h while stirred at a speed of 600 rpm. The
resulting mixture was cooled down and was then poured into a 250 mL round-bottom
flask fitted with a simple distillation apparatus under vacuum. The resulting NBE-

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CH2OH was distilled twice, yielding a viscous and colorless oil (yield 56 %)
(Endo/exo: 82/18).
1
Endo : H NMR (300 MHz, CDCl3, δ): 6.06 (dd, J = 5.6, 3.0 Hz, 1H), 5.89 (dd, J =
5.6, 2.9 Hz, 1H), 3.28 (dt, J = 17.4, 8.7 Hz, 1H), 3.13 (t, J= 8.6 Hz, 1H), 2.86 (d, J =
22.1 Hz, 1H), 2.72 (s, 1H), 2.22 (s, 1H), 1.74 (ddd, J = 11.8, 9.2, 3.8 Hz, 1H), 1.13-
1.38 (m, 3H), 0.46 (ddd, J = 11.8, 4.3, 2.7 Hz, 1H) (See Figure S1); 13C NMR (60
MHz, CDCl3, δ) 132.2, 137.2, 66.0, 49.4, 43.5, 42.2, 41.5 and 28.8 (See Figure S2).
2.4 Synthesis of norbornene-5-methylene bromide (NBE-CH2Br)
In a pressurized Parr reactor DCPD (100 g, 0.76 mol, 1.0 eq) and allyl bromide (128
g, 1.06 mol, 1.4 eq) were added in the reactor and heated at 210 °C for 2 h while
stirred at a speed of 600 rpm. The resulting oil was purified by simple distillation
under vacuum. (Yield 55 %) (endo/exo : 86/14).
1
Endo : H NMR (300 MHz, CDCl3, δ): 6.20 (dd, J = 5.7, 3.0 Hz, 1H), 5.98 (dd, J =
5.7, 2.9 Hz, 1H), 3.23 (dd, J = 9.5, 6.8 Hz, 1H), 3.06 (t, J = 9.6 Hz, 1H), 2.97 (s, 1H),
2.86 (s, 1H), 2.62 – 2.46 (m, 1H), 2.04 – 1.91 (m, 1H), 1.52 (ddd, J = 8.2, 4.0, 1.9 Hz,
1H), 1.33 (d, J = 8.3 Hz, 1H), 0.62 (ddd, J = 11.8, 4.3, 2.7 Hz, 1H) (See Figure S3);
13C NMR (60 MHz, CDCl3, δ) 131.6, 138.2, 49.7, 45.5,43.2, 42.2, 38.2 and 32.8 (See
Figure S4).
2.5 Synthesis of 5-hexyl-norbornene (NBE-Hxl)
In a pressurized Parr reactor, DCPD (100 g, 0.76 mol, 1.0 eq) and 1-octene (119 g,
1.06 mol, 1.4 eq) were heated at 200 °C for 4 h and stirred at a speed of 600 rpm. The
resulting oil was purified by simple distillation under vacuum. (Yield 55 %)
(endo/exo: 86/14).

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1H NMR (300 MHz, CDCl3, δ) 6.15 (dd, J = 5.6, 3.0 Hz, 1H), 5.97 (dd, J = 5.7, 2.8
Hz, 1H), 2.80 (s, 2H), 1.52 – 1.22 (m, 12H) 1.21 – 1.02 (m, 2H) 0.94 (t, J = 6.5 Hz,
3H), 0.55 (ddd, J = 11.1, 3.8, 2.5 Hz, 1H) (See Figure S5). 13C NMR (60 MHz,
CDCl3, δ) 132.4, 136.7, 49.6, 45.5, 42.6, 38.9, 34.9, 32.5, 32.0, 29.7, 28.7, 22.8 and
14.1 (See Figure S6) .
2.6 Preparation of the catalytic solution
The catalytic solution used for the polymerizations (c = 0.05 mol/L) was prepared by
mixing in a vial allyl palladium chloride dimer (184 mg, 1 mmol, 1 eq) and silver
hexafluoroantimonate (AgSbF6) (515 mg, 1.5 mmol, 1.5 eq) with 20 mL of
anhydrous nitromethane. The mixture was then filtered to remove the silver chloride
precipitate and the solution was stored under nitrogen atmosphere.
2.7 Typical polymerization procedure of NBE-CH2OH, NBE and NBE-Hxl
In a 100 mL round bottom flask, NBE (15 g, 0.159 mol), NBE-CH2OH (6.1 g, 0.049
mol) and NBE-Hxl (6.5 g, 0.037 mol) were added under vigorous stirring under
nitrogen. Once the NBE was completely solubilized in the liquid monomers, (4.9 mL,
0.244 mmol) of the catalytic solution was added dropwise. The mixture quickly
turned to a dark orange color and the reaction was heated overnight at 70 °C. The
reaction mixture turned solid, due to the vitrification effect. The solid mixture was
dissolved in a minimal amount of chlorobenzene then poured in 8 to 10 volumes of
methanol (acetone can also be used). The precipitate was washed 3 times with
1
methanol and then dried under vacuum to yield a slightly greyish powder. H NMR
(300 MHz, CDCl3, δ) 3.15-3.45 (m, 2H, CH2OH), 2.23 (s, 2H, -CH2CHCH2OH),
1.76 (m, 2H, bridgehead), 1.58 (s, 1H, -CHCH2OH), 0.90 (s, 3H, CH3 (hexyl end
chain)), all the others peaks are 1H from the bicyclic unit (See Figure S13). IR (ATR):
ν = 3490, 2925, 2866, 1452, 1377, 1297, 1096 cm-1 (See Figure S14) .

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2.8 Mesylation of the polymer
In a round bottom flask fitted with a condenser, a typical polymer containing
hydroxyl group (1 g) was added to THF (25 mL) and toluene (125 mL). Once
solubilized, triethylamine (Et3N) (1.8 g) was added dropwise to the solution followed
by a slow addition of mesyl chloride (MsCl) (1 g). Under vigorous stirring, the
solution was heated to reflux for 6 h. The resulting mixture was cooled down and
concentrated to a small volume under vacuum and then poured into 8 to 10 volumes
of methanol to precipitate. The polymer is washed 3 times and dried under vacuum at
ambient temperature. Yield = 0.92 g. 1H NMR (300 MHz, CDCl3, δ) 4.0-4.4 (m, 2H,
1
-CH2Oms), 3.02 (s, 3H, -OSO2CH3), 2.23 (bridgehead H), 1.0-2.1 (all other
protons), 0.90 (s, 3H, CH3 (hexyl end chain)) (See Figure S15) . IR (ATR): ν = 2942,
2867, 1453, 1354 (S=O), 1173 (S=O), 1027, 939, 816 (S-OR) cm-1 (See Figure S16) .
2.9 Thioacetylation of the polymer
In a round bottom flask, potassium thioacetate (0.8 g) was added to toluene (125 mL)
and DMF (25 mL) and the slurry was degassed with nitrogen for 1 h. The solution
turned turquoise. The mesylated polymer (0.9 g) was then added and the mixture was
heated to reflux under nitrogen for 12 h. The mixture was then cooled down and
concentrated under vacuum to a small volume and then poured into 8 to 10 volumes
of methanol. The collected precipitate was washed 3 times and dried under vacuum.
Yield = 0.9 g. 1H NMR (300 MHz, CDCl3, δ) 2.82 (m, 2H, -CH2SC(O)CH3), 2.34 (s,
3H, SC(O)CH3), 1.0-2.3 (all other protons), 0.90 (s, 3H, CH3 (hexyl end chain)) (See
Figure S17) . IR (ATR): ν = 2942.2, 2865.7, 1691.9 (C=O, thioacetate), 1454, 1260,
1096 (CH2-S, thioacetate), 1014 (CH2-S, thioacetate) (See Figure S18).
2.10 Sulfonation reaction
In a round bottom flask, the thioacetylated polymer (0.9 g) was added to a mixture of
isopropanol (50 mL), aqueous H2O2 30% v:v (17 mL) and acetic acid (34 mL). The
resulting mixture was heated to 65 °C for 12 h. The reaction was then cooled down to

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room temperature and concentrated under vacuum to a small volume and then poured
into methanol. The polymer is washed 3 times and dried under vacuum. Yield = 0.8
1
g. H NMR (300 MHz, CDCl3, δ) 3.3 (m, 2H, -CH2SO3H) (See Figure S19) IR
(ATR): ν = 3418 (Water remaining and O-H bond), 2943, 2886, 1722 (Acetic acid
remaining), 1453, 1367 (S=O), 1298, 1243 (-SO3H), 1171 (S=O), 1093, 1029 (-
SO3H) (See Figure S20) .
3. RESULTS AND DISCUSSION
3.1 Copolymerization of NBE and NBE-CH2OH
The preparation of the sulfonated copolymer is outlined in Scheme 1. The copolymer
is prepared by the copolymerization of NBE and NBE-CH2OH using the naked Pd
catalyst (η3-allyl)PdSbF6 in the presence of a small amount of nitromethane. This
catalyst has been shown to promote the polymerization of substituted polar NBEs as
well as the rectification-insertion mechanism [19,21,22] with efficiency. In this study,
NBE-CH2OH (82% endo, 18% exo) was obtained in a one-step non-optimized
procedure in 56% yield by direct Diels-Alder reaction of DCDP with allyl alcohol.
Due to the rectification-insertion mechanism, it is not necessary to use pure exo NBE-
CH2OH, a compound which was prepared in the past by a five step procedure in 22%
yield overall [12].
Using the naked Pd catalyst (η3-allyl)PdSbF6 at a concentration of 0.1 mol%, NBE-
CH2OH was found to be readily copolymerized with NBE (Table 1). The
1
composition of the copolymer was determined by H NMR by integration of the
characteristic CH2OH resonance at 3.15-3.45 pm relative to the integral of all other
resonances (see Calculations and Equations, Supplementary Content section).
Interestingly, the composition of the copolymer is similar to the monomer feed ratio,
indicating that globally the reactivity of NBE-CH2OH is similar to NBE (within
experimental uncertainty for the determination of the composition of the copolymer),
however a microstructure analysis would be necessary to further assess the reactivity

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of NBE-CH2OH and NBE. This microstructure analysis is rendered extremely
1
13
difficult due to the broadness of the H and C polymer resonances stemming from
1
the bicyclic backbone rigidity (see Supplementary Data for examples of H and 13C
spectra of the polymer). Classical kinetic analysis (such as Kelen-Tudos or Fineman-
Ross plots) cannot be simply performed in our case, as the endo monomer is
converted in exo comonomer during the polymerization: thus, the copolymerization
kinetics is more complicated than the usual copolymerization models.
Copolymers containing as much as 42 mol% OH groups were prepared. Polymers
with higher OH incorporations were not prepared as they would lead to water soluble
sulfonated polymers which are unsuitable as PEM. The polymerization yields are
typically comprised between 40 to 70%. The polymerization stops because the
reaction mixture becomes solid (vitrification point).

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Table 1 Catalytic copolymerization of NBE-CH2OH or NBE-CH2Br with NBEa
c
c
Monomer ratio (%)
Yield
Polymer composition
Mn
Mw
(mol%)b
Expt
X
NBE
NBE-X
(%)
NBE
NBE-X
(g/mol)
(g/mol)
1
2
3
4
5
6
7
8
OH
OH
OH
OH
OH
OH
Br
95
90
85
80
70
60
95
90
5
71
72
65
58
51
42
66
55
93
86
82
77
68
57
97
91
7
13,590
14,990
16,870
25,790
28,720
24,780
36,670
73,090
66,970
57,970
71,830
132,000
155,300
90,390
10
15
20
30
40
5
14
18
23
32
43
3
127,600
198,700
Br
10
9
9
Br
Br
Br
80
70
50
70
70
70
70
20
30
50
30
30
30
30
47
51
29
27
38
26
59
88
77
60
80
81
83
79
12
23
40
20
19
17
21
14,390
3,770
2,870
1,280
1,880
1,560
1,460
94,670
20,450
13,480
10,820
27,560
18,420
16,670
10
11
12
13
14
15
Brd
Bre
Brf
Brg
a Polymerization conditions : no solvent, molar ratio monomer / catalyst = 1000 / 1, T = 70 °C, t = 3 h when X =
OH, t = 12 h when X = Br.
b Molar composition determined by 1H NMR at ambient temperature in CDCl3.
c Determined by GPC at 40 °C in CHCl3.
d Molar ratio monomer / catalyst = 2000 / 1
e Molar ratio monomer / catalyst = 4000 / 1
f Molar ratio monomer / catalyst = 5000 / 1
g Molar ratio monomer / catalyst = 10000 / 1
The hydroxyl groups present in the polymer were then subjected to the mesylation
step. Different conditions were tried (ambient temperature, reflux, toluene, THF,
mixture of THF and toluene), however this reaction led to no modification of the
1
hydroxylated copolymer: both H NMR and FTIR spectroscopy indicated that the
hydroxyl groups remained intact. This poor reactivity is attributed to the low
solubility of the copolymer in toluene which itself is due the high rigidity of the
bicyclic backbone. It will be seen below that hydroxylated copolymers also

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containing alkylated NBE units (as solubilizing units) are readily mesylated under
similar conditions.
3.2 Copolymerization of NBE and NBE-CH2Br
The unsuccessful attempts to perform the mesylation step of a copolymer of NBE and
NBE-CH2OH led us to investigate another route toward the fabrication of sulfonated
PNBE ionomers. Thus, copolymers of NBE and NBE-CH2Br were prepared. Using
the same catalyst, we copolymerized NBE and NBE-CH2Br (Scheme 1 and Table 1).
Similarly to NBE-CH2OH, NBE-CH2Br (86% endo) was directly prepared by Diels-
Alder reaction of DCPD with allyl bromide. The composition of the polymer
corresponds to the monomer feed, but the molecular weight of the polymer decreases
with increasing halogenated monomer content. It is known that CH3-I can undergo
oxidative addition with alkyl Pd(II) complexes [23] to form Pd(IV) species which are
unstable. Upon reductive elimination of R-CH3, they generate another Pd(II)
complex. In our case, oxidative addition of NBE-CH2Br to the Pd(II) naked catalyst
followed by reductive elimination would lead to the formation of a terminated
+
polymer chain and a PdBrS3 complex (S = solvent), which is known to be able to
initiate the polymerization of NBE [24-26]. Therefore, the monomer NBE-CH2Br
could also act as a chain transfer agent, which is consistent with the low molecular
weight observed for the NBE-CH2Br / NBE copolymers (Expts 9-11) when compared
to NBE-CH2OH / NBE copolymers (Expts 1-6). Molecular weight distribution
analysis by GPC also confirms the occurrence of chain transfer with NBE-CH2Br.
When the amount of NBE-CH2Br in the monomer feed is low (Expt 7 and 8, Figure
S25), essentially monomodal distributions are observed. The molecular weights are
higher than those obtained with NBE-CH2OH monomer (Figure S24). However, with
increasing amounts of NBE-CH2Br in the monomer feed, the molecular weight
distribution becomes bimodal, as a fraction of chains with very low molecular weight
appears (Figure S25 and S26). Such chains are probably resulting from chain transfer
to monomer, which becomes predominant when the concentration of NBE-CH2Br in

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the monomer feed is high. Interestingly, despite the presence of a transfer reaction,
the reaction could nonetheless proceed at very low catalyst loadings (as low as 0.01
mol%, yield = 59%, Expt 15).
The -CH2Br groups from the poly (NBE-co-NBE-CH2Br) are then transformed into
thioacetate groups through a second order nucleophilic substitution (SN2) using
potassium thioacetate in a toluene - DMF mixture. The conversion into thioacetate is
1
quantitative as shown by the complete disappearance in H NMR of the -CH2Br
broad resonance between 3.2 and 3.6 ppm (Figure S9) and the appearance of a peak
around 2.8 ppm corresponding to -CH2SC(O)CH3 proton (Figure S17). By FTIR, the
thioacetate polymer shows a strong band at 1694 cm-1 (Figure S18) characteristic of
the C=O band of the thioacetate group.
Sulfonation could then be performed by oxidation of the thioacetate with H2O2.
Attempts to characterize and to prepare films with the sulfonated polymers failed due
the absence of solubility in any common organic solvent in which PNBEs are usually
soluble such as THF, chloroform, DMF or chlorobenzene. Therefore, we attempted to
prepare films from the thioacetate polymer, so as to subsequently transform them into
sulfonated membranes. Solutions of thioacetylated PNBE in various solvents (toluene
at 110 °C, THF, chlorobenzene, o-dichlorobenzene) were casted in a glass petri dish
and the solvent was left to evaporate. The resulting transparent and glassy thin films
were extremely brittle, and could not be manipulated without breakage. By DSC, no
o
transition was observed for this polymer in a temperature range of 25 to 300 C,
consistent with a Tg higher than 300 oC.

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Scheme 2. Preparation of sulfonated norbornene terpolymers (a) Toluene, THF (both
anhydrous), Mesyl Chloride, Et3N, reflux, 6 h. (b) Toluene, DMF (both anhydrous),
Potassium thioacetate, reflux 12 h. (c) H2O2 30% w/w in H2O, AcOH, iPrOH, 65 oC,
12 h.
Table 2 Catalytic copolymerization of NBE and NBE-Hxla
c
c
Monomer ratio (%) Yield Polymer composition
Mn
Mw
Tgd
(mol%)b
NBE
NBE-Hxl (%)
NBE
NBE-Hxl
(g/mol)
(g/mol)
(°C)
Expt
90
70
10
30
82
70
86
68
14
32
19,880
10,300
178,300
29,930
221
183
1
2
50
30
10
50
70
90
56
42
37
46
27
8
54
73
92
5,930
5,150
5,660
24,440
12,920
12,470
168
156
144
3
4
5
a Polymerization conditions : no solvent molar ratio monomer / Catalyst = 1000 / 1, T = 70 °C, t = 12 h
b Molar composition determined by 1H NMR at ambient temperature in CDCl3.
c Determined by GPC at 40 °C in THF.
d Glass phase transition temperatures measured by DSC

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3.3 Terpolymers of NBE, NBE-CH2OH and NBE-Hxl
In order to improve the processability of the ionomers, terpolymers of NBE
containing one NBE bearing a hexyl pendant group in 5 position (NBE-Hxl) were
prepared (Scheme 2). The hexyl group is responsible for an increase of free volume
resulting in a Tg decrease [16, 27]. In order to precisely assess the influence of the
presence of a side chain on the Tg, copolymers of NBE and NBE-Hxl with various
amounts were first prepared. As expected, the Tg decreases as the amount of NBE-
Hxl increases. The relation between 1/Tg vs weight fraction of NBE-Hxl in the
polymer is linear (r2 = 0.94) and follows the Flory-Fox law for statistical copolymers
o
(calculated Tg for PNBE and PNBE-Hxl are respectively 240 and 136 C). The
calculated Tg for PNBE is surprisingly low, as PNBE prepared with Pd naked
o
catalyst is known to exhibit a Tg higher than 300 C, as shown above [27]. It should
be noted that as the amount of NBE-Hxl increases, the polymerization becomes
slower, and both the yield and the degree of polymerization Xn decrease. For
example, when the amount of inserted NBE-Hxl is 14% or 92%, Xn = 207 or 35,
respectively. This decrease in catalytic activity and molecular weight for high NBE-
Hxl concentrations is due to the presence of an endo NBE-Hxl isomer which is
difficult to rectify in the insertion-rectification process because of the high activation
energy to achieve the retro Diels-Alder reaction.

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Table 3 Catalytic copolymerization of NBE-CH2OH with NBE and NBE-Hxla
c
c
Expt
Monomer ratio
Yield
Polymer composition
(mol%)b
Mn
Mw
g/mol (°C)
Tgd
Tge
(mol%)
(%)
g/mol
NBE NBE NBE-
NBE
NBE
OH
8
NBE-
Hxl
60
(°C)
OH
Hxl
1
2
3
4
5
6
50
50
50
30
30
30
10
40
72
75
66
40
52
48
32
47
22
30
19
17
9,100
25,900
3,400
27,130 122 152
62,920 137 191
6,800 188 220
27,060 120 126
30,380 131 156
43,890 141 164
20
30
10
20
30
30
20
60
50
40
20
38
5
33
40
65
65
40
14,100
21,250
17,360
16
43
a Polymerization conditions : no solvent molar ratio monomer / catalyst = 1000 / 1, T = 70 °C, t = 12 h
b Molar composition determined by 1H NMR in CDCl3.
c Determined by GPC at 40 °C in THF.
d Glass transition temperature of the hydroxylated terpolymers measured by DSC
e
Glass transition temperature of the thioacetylated terpolymers measured by DSC
Attempts to prepare terpolymers of NBE, NBE-CH2Br and NBE-Hxl led to poor
results. The highest yield (12%) was obtained for NBE: NBE-CH2Br: NBE-Hxl = 70:
20: 10 mol%. Increasing the amount of NBE-CH2Br or NBE-Hxl led to a complete
loss of activity, which can probably be explained by the combination of chain transfer
activity with NBE-CH2Br (see above) and the low activity of NBE-Hxl monomer.
We therefore investigated the terpolymerization of NBE, NBECH2OH and NBE-Hxl,
with the assumption that the transformation of the CH2OH group into sulfonic group
would be possible for a terpolymer due to its higher solubility. In stark contrast with
terpolymerizations performed with NBE-CH2Br, terpolymerizations with NBE-
CH2OH proceeded smoothly, with isolated yields comprised between 40 and 75%
1
(Table 3). These new terpolymers were then submitted to mesylation attempts. H
NMR and FTIR revealed a quantitative transformation into mesylate groups. The
broad resonance around 3.5 ppm attributed to the CH2OH protons (Figure S13)

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disappear and give way to two new resonances, one broad one around 4.2 ppm for the
CH2-OS(O2)CH3 protons and the other one at 3.0 ppm corresponding to CH3 group
bound to the sulfur (Figure S15). This result is confirmed by FTIR, with the
appearance of three bands at 1354 and 1173 and 817 cm-1 respectively for the S=O
and for the S-OR fragments (Figure S16). The transformation of the mesylate into the
thioacetate group also proceeded smoothly. The complete disappearance of the
1
resonances at 4.2 and 3.0 ppm in H NMR is observed concomitantly to the
appearance of a broad resonance between 2.8 and 3.1 ppm for the CH2-SC(O)-CH3
protons and a sharp one at 2.34 ppm for the –C(O)-CH3 protons (Figure S17). The
characteristic bands of the thioacetate group, namely the C=O bond at 1694 cm-1 and
the S-CH2 bond at 1096 cm-1 are also observed in FTIR (Figure S18). Sulfonations
were performed on the polymers in their powder form. FTIR reveals the apparition of
bands characteristic to the sulfonic acid at 1243 and 1029 cm-1. Bands at 1367 and
1
1171 cm-1 coming from the S=O bond are present (Figure S20). H NMR clearly
shows the disappearance of the characteristic resonances of the thioacetate group
mentioned earlier (Figure S19).
3.4 Preparation of the sulfonated ionomers
The transformation of the hydroxylated terpolymer to the sulfonated terpolymer
(mesylation, thioacetylation, and oxidation) occurred in quantitative fashion.
Therefore, starting from monomers, the sulfonated terpolymer was obtained in 40-
75% yield in four steps, none of them requiring extreme or harsh operating conditions
(high temperature, high vacuum or corrosive sulfonating agent). When the sulfonated
polymer is extensively dried under vacuum, it resists redissolution in most common
organic solvents (THF, toluene, chloroform and chlorobenzene). This feature is not
unusual for ionomers due to the formation of intermolecular H-bonds which acts as
cross-links [28]. However, the thioacetylated terpolymer could be solvent-cast from
o
chlorobenzene at 70 C, leading to brittle films which could then be oxidized into
sulfonated ionomers using the procedure above (reaction time 48 hours). The

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properties of these films as PEMs for fuel cells will be evaluated in a subsequent
work. However, it is worth mentioning that these sulfonated ionomers possess several
interesting properties which make them suitable candidates for the preparation of
PEM for fuel cells. First, they exhibit good thermal stability, with an onset of
o
degradation at 275 C, as measured by thermal gravimetry analysis (using a fully
dehydrated sample, Figure S32). Second, the terpolymerization procedure permits a
facile modulation of the amount of SO3H groups incorporated in the polymer. As the
result, the ion exchange capacities (IEC), measured by NaOH titration, could be
varied from 0.55 to 2.23 meq.g-1 (Table 4). The measured IEC are in good agreement
with the theoretical IEC, which itself corresponds well with the monomer feed. Third,
the terpolymers do not swell excessively in water, as shown by a low water uptake
after immersion of the polymer for 5 days in water at room temperature (Table 4).
Last, the sulfonated polymers have high Tg, as shown by the absence of any
o
o
transition in the range 25 - 275 C (the polymers remain hard at 275 C).
Interestingly, the Tg of the hydroxylated terpolymer (see Table 3, column 10) and the
Tg of the thioacetylated terpolymer (column 11) is lower. Such Tg increase is
expected for an ionomer [28]. In our hands, the hydroxylated or the thioacetylated
polymers were eventually processed under the form of films using conventional
thermal presses. However, these films, which could be sulfonated in the solid state,
were found to be very brittle and were found to be unsuitable for ionic conductivity
measurements.

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Table 4
Results on IECs and water uptakes measurements performed on sulfonated
terpolymers under their film form (see Table 3 for terpolymer composition).
Expt
IEC (theoretical)
Water
uptake (%)
2.2
SO3H (mol %)
IEC (meq.g-1)
(meq.g-1)
1
2
3
4
5
6
8
0.60
1.47
2.79
0.44
1.18
3.20
0.91
1.52
2.23
0.55
1.23
1.92
3.5
1.7
2.8
3.4
20
38
5
16
43
2.7
To conclude, this study demonstrates that sulfonated high Tg ionomers can be
obtained from the norbornene insertion copolymers obtained by catalytic rectification
insertion polymerization. The synthesis is remarkably facile and potentially scalable,
as monomers can be obtained from fundamental organic intermediates in one step (50
% yield), and the ionomers can be obtained in four steps (40-75% yield). The
resulting sulfonated polynorbornenes exhibit very high Tg (above decomposition
temperature of 275 oC). Furthermore, the synthesis allows for the facile tuning of the
SO3H content. This preliminary set of properties make these hydrophobic sulfonated
insertion polynorbornenes interesting candidates for high temperature PEMs for fuel
cells.
APPENDIX A. SUPPLEMENTARY DATA
The following is the supplementary data related to this article. It includes details
about NMR, DSC, TGA, IEC and water uptake measurements, equations leading to
the molar composition of the copolymers with respect to 1H NMR integral values as
well as NMR spectra, DSC, TGA and GPC traces. This material is available free of
charge via the internet.

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ACKNOWLEDGEMENTS
The authors wish to thank the Fonds de la Recherche du Québec Nature et
Technologies (Equipes Program) for funding. FP thanks NanoQAM and UQAM for
fellowships.
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RESEARCH HIGHLIGHTS
•
We developed a simple method to prepare sulfonated ionomers based on insertion
polynorbornenes (40-75% overall yield)
•
•
These ionomers have very high Tg (above decomposition temperature)
The content of SO3H group in the polymer can easily be controlled by adjusting the
monomer feed