Radical copolymerization of 2,2,2-trifluoroethyl methacrylate with cyano compounds for dielectric materials: Synthesis and characterization

Article abstract of DOI:10.1016/j.jfluchem.2005.12.032

The copolymerization of cyano (nitrile) monomers and a fluoroalkylmethacrylate is used to develop new dielectric polymers containing C-CN and C-F substituents. Methacrylonitrile (MAN), acrylonitrile (AN) and methylvinylidene cyanide (MVCN) were chosen as cyano monomers. 2,2,2-Trifluoroethyl methacrylate (MATRIF) was used as a fluorinated comonomer. The copolymers based on cyano monomers such as AN, MAN or MVCN, and MATRIF comonomers were synthesized by radical process initiated by AIBN. The yields of the copolymerizations were ranging between 40 and 60%. These copolymers were characterized by ¹H, ¹³C, ¹⁹F NMR and IR spectroscopy which showed that the percentages of incorporation of AN and MAN in the copolymers were 45%. However, only 5% of MVCN was incorporated into poly(MVCN-co-MATRIF) copolymer. Thermogravimetric analyses showed that the thermal decomposition occurred from 200, 230 or 240°C for copolymers of MVCN, MAN or AN, respectively, and indicated that the process of degradation depends on the nature of cyano monomer.

Full text of DOI:10.1016/j.jfluchem.2005.12.032

Journal of Fluorine Chemistry 127 (2006) 391–399
www.elsevier.com/locate/fluor
Radical copolymerization of 2,2,2-trifluoroethyl methacrylate with cyano
compounds for dielectric materials: Synthesis and characterization
M. Raihane a, B. Ameduri b,
*
a Laboratory of Bioorganic and Macromolecular Chemistry, Faculty of Sciences and Techniques, Avenue Abdelkrim Khattabi,
BP 549 40000 Marrakech, Morocco
´
Laboratory of Macromolecular Chemistry, UMR (CNRS) 5076, Ecole Nationale Superieure de Chimie de Montpellier, 8 Rue Ecole Normale,
b
34296 Montpellier Cedex 5, France
Received 23 September 2005; received in revised form 16 December 2005; accepted 20 December 2005
Available online 9 March 2006
Abstract
The copolymerization of cyano (nitrile) monomers and a fluoroalkylmethacrylate is used to develop new dielectric polymers containing C–CN
and C–F substituents. Methacrylonitrile (MAN), acrylonitrile (AN) and methylvinylidene cyanide (MVCN) were chosen as cyano monomers.
2,2,2-Trifluoroethyl methacrylate (MATRIF) was used as a fluorinated comonomer. The copolymers based on cyano monomers such as AN, MAN
or MVCN, and MATRIF comonomers were synthesized by radical process initiated by AIBN. The yields of the copolymerizations were ranging
1
between 40 and 60%. These copolymers were characterized by H, 13C, 19F NMR and IR spectroscopy which showed that the percentages of
incorporation of AN and MAN in the copolymers were 45%. However, only 5% of MVCN was incorporated into poly(MVCN-co-MATRIF)
copolymer. Thermogravimetric analyses showed that the thermal decomposition occurred from 200, 230 or 240 8C for copolymers of MVCN,
MAN or AN, respectively, and indicated that the process of degradation depends on the nature of cyano monomer.
# 2006 Elsevier B.V. All rights reserved.
Keywords: Radical copolymerization; 2,2,2-Trifluoroethyl methacrylate; Cyano (or nitrile) monomers; Nuclear magnetic resonance spectroscopy; Thermal
properties
1. Introduction
acterized by 13C NMR. The best piezoelectric and dielectric
properties were characterized with copolymers including vinyl
esters [7] and substituted styrenes [8]. Other cyano monomers
such as methacrylonitrile and acrylonitrile copolymerized with
vinyl or isopropenylacetate [9] and some of the resulting
copolymers showed interesting pyroelectric properties [10]. In
addition, copolymers based on methylvinylidene cyanide and
vinyl acetate [11] or styrene [5] exhibit interesting dielectric
behavior [12].
Polymers containing polar substituents such as cyano
(nitrile) groups are of interest for the development of advanced
electrical and optical materials because of the large dipole
moment arising from the polar substituent (CN) [1]. Due to the
piezoelectric activity of the amorphous and alternating
copolymer of vinylidene cyanide (VCN) and vinyl acetate,
first described by Miyata et al. [2], there has been growing
interest in the copolymerization of cyano monomers with
various acrylic, vinylic or styrenic to study their microstruc-
tures or their pyroelectric and dielectric properties. Vinylidene
cyanide has been copolymerized with comonomers such as
vinylic esters [3], styrene [4], substituted styrenes [5] and
methacrylic derivatives [6]. All these copolymerizations gave
alternating copolymers and their microstructures were char-
The amorphous copolymers have to be poled to active
noncentrosymmetric forms, driving their piezo- or pyroelectric
properties from the cyano dipole. The poling was carried out at
a temperature just below the glass transition temperature of the
(co)polymers. After cooling, a fraction of dipole was aligned in
the field section [2]. The properties of copolymers containing
cyano groups could be improved with a higher concentration of
dipoles. The copolymerization reaction of cyano monomers
with captodative monomers such as 1,1-disubstituted ethylene
having an electron-withdrawing (capto) and an electron-donor
(dative) substituent on the same carbon, could provide new
* Corresponding author. Tel.: +33 4 6714 4368; fax: +33 4 6714 7220.
E-mail address: bruno.ameduri@enscm.fr (B. Ameduri).
0022-1139/$ – see front matter # 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2005.12.032

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M. Raihane, B. Ameduri / Journal of Fluorine Chemistry 127 (2006) 391–399
materials with interesting electric properties. Copolymers of
vinylidene cyanide, methacrylonitrile and acrylonitrile with
captodative monomers such as a-cyanovinyl acetate [13] and
ethyl a-acetoxyacrylate [14] were synthesized by radical
copolymerization. The microstructure of the resulting copoly-
mers was characterized by 13C NMR, and some reactivity ratios
could be assessed. The copolymers of vinylidene cyanide
exhibit a highly alternating structure, in contrast to those of
copolymers based on methacrylonitrile and acrylonitrile which
were more statistic than alternating.
acrylonitrile (AN) and methylvinylidene cyanide (MVCN)
were chosen as cyano monomers. 2,2,2-Trifluoroethyl metha-
crylate (MATRIF) was used as a fluorinated comonomer. The
copolymers of cyano monomers with electron-donating
monomers such as methyl acrylate [10], or captodative
monomers as methyl a-acetoxylacrylate [19,33], were also
achieved. However, no fluorinated acrylate monomer was used
and that topic represents the objective of this article to elaborate
new dielectric fluoronitrile materials.
Other polymers or copolymers having crystalline structures
with large dipole moments can also exhibit high piezo-
electricity when their main chain exhibits an all-trans
conformation. Well-known examples are the poly(vinylidene
fluoride) (PVDF) [15], especially b-type and the crystalline
copolymers of vinylidene fluoride and trifluoroethylene [16–
18]. Vinylidene cyanide was copolymerized with two styrenic
comonomers bearing a fluorinated chain in the para position of
aromatic nuclei. The microstructure of the resulting copoly-
mers was studied by 13C NMR and for one copolymer, a partial
crystallinity was observed, due to their side fluorinated chain
[19].
2. Results and discussion
2.1. Synthesis of monomers and copolymers
VCN is difficult to prepare and is highly reactive [34].
However, methylvinylidene cyanide (MVCN) was synthesized
in one step, using the Knovenagel reaction, from acetaldehyde
and malononitrile as a compound possessing mobile hydrogen,
in the presence of b-alanine as base [35]. The yields were close
to 80% and better than those obtained when diethylamine was
used (65%) [9]. This monomer was significantly less reactive
than VCN. We have used a weak base such as an amino acid to
avoid oligomerization of MVCN.
Polymerization of many fluorinated acrylic monomers was
studied for their physical properties. The performance of a
series of acrylic-based copolymers as protective coating
materials for stone or ancient buildings has been carried out
by comparing them with unfluorinated polymeric analogues
[20,21]. For this purpose, a series of copolymers of
1H,1H,2H,2H-perfluorodocedyl methacrylate and 2,2,2-tri-
fluoroethyl methacrylate with non-fluorinated vinyl ether or
acrylic monomers were synthesized, and applied to limestone
and marble substrates for interesting coating applications [22].
Several fluoroalkylacrylate and methacrylate polymers were
developed and their physical properties studied [23–31].
Dielectric relaxation studies were achieved on a series of
poly(fluoroalkylmethacrylate)s. The a above Tg and g
relaxations below Tg were observed and assigned to reorienta-
tion of segments and local molecular motion of fluoroalkyl side
groups [32].
Under free radical conditions (AIBN, 60 8C) or from
photoinduced process [9] MVCN did not undergo any
polymerization. When (C6H5)3P, NaCN or 1,4-diazabicy-
clo[2,2,2]octane (DABCO) were used as possible anionic
initiators, the bulk polymerization slowly showed an increase of
viscosity and turned glassy (mainly trimer) [9]. Interestingly, its
copolymerization with electron-rich monomers readily led to
high molecular weight-copolymers in high yields.
2,2,2-Trifluoroethyl methacrylate (MATRIF) can be synthe-
sized from methacryloyl chloride and 2,2,2-trifluoroethanol
under nitrogen in the presence of triethylamine as base and 2,6–
di-tert-butyl-4-methylphenol as inhibitor, according to proce-
dure previously reported [21]. The purification of the MATRIF
monomer was carried out by distillation (b.p.: 100–102 8C/
1 atm).
Copolymers were prepared from equimolar proportions of
cyano monomers and MATRIF mixed with 1 wt.% of initiator
(AIBN) dissolved in a minimum of acetonitrile and heated at
80 8C for 12 h (Scheme 1). The yields of the copolymerizations
were ranging between 40 and 60%.
To develop new dielectric polymers containing C–CN and
C–F substitutents with strong dipole moments, we describe in
this paper the radical copolymerization of cyano (or nitrile)
monomers and a fluoromethacrylate. Methacrylonitrile (MAN),
Scheme 1. Synthetic routes of copolymers based on MATRIF.

M. Raihane, B. Ameduri / Journal of Fluorine Chemistry 127 (2006) 391–399
393
Fig. 1. Infrared spectrum of poly(AN-co-MATRIF) copolymer.
2.2. Spectroscopic characterizations, microanalyses and
GPC
6.2 ppm for AN; 5.8 ppm for MAN; 2.25 and 7.7 ppm for
MVCN; 5.6 and 6.2 ppm for MATRIF) were absent in these
spectra. The resonance of methylenic protons of the main chain
was observed in the range 0.8–1.5 ppm. The singlet at 2.9 ppm
was attributed to water present in the solvent (DMSO). The
composition of the copolymers can be calculated by measuring
Fig. 1 represents the infrared spectrum of poly(AN-co-
MATRIF) copolymer. Vinylic bond absorbances (C C) of
MATRIF and AN at 1638 and 1620 cmꢀ1, respectively, are
absent, indicating that the copolymerization reaction has
occurred. Characteristic bands of this copolymer are
2989 cmꢀꢀ11 (aliphatic C–H stretch), 2243 cmꢀ1 (CBB N stretch),
1
integrals of some characteristic peaks in the H NMR spectra.
For example, in poly(AN-co-MATRIF) copolymer, the areas of
the signals of CH3 assigned to MATRIF (I1) in the range 0.8–
1.5 ppm and the methylenic protons CH2 (I2) in the range 1.5–
2.4 ppm show that the calculated percentage of AN in the
copolymer, using equation below, is close to 44.
1754 cm
(C O), 1456–1417 cmꢀ1 (out-of-plane C–H),
1286 cmꢀ1 (aliphatic C–F stretch), 1170–1127 cmꢀ1 (C–O)
and 973 cmꢀ1 (out-of-plane C–H bond). Similar observations
can be made for the IR spectrum of poly(MVCN or MAN-co-
MATRIF) copolymers.
3I2 ꢀ 2I1
AN ðmol %Þ ¼
ꢁ 100
(1)
3I2
The 19F NMR spectra of these copolymers exhibit a signal
centred at ꢀ73 ppm corresponding to CF3 group.
The result of elemental analysis (%N = 5.1) of the poly(AN-
co-MATRIF) copolymer is in good agreement within this
incorporation ratio. Table 2 shows the molar percentage of
incorporated cyano monomer calculated from elemental
analyses and assessed by 1H NMR in the copolymers of
MATRIF. The copolymer compositions of acrylonitrile with
non-fluorinated acrylic such as ethyl acrylate [38] and methyl
methacrylate [39] were calculated using elemental analyses.
The incorporation of AN was close to 41 and 53%, respectively,
and shows that the lateral CF3 group affects slightly the
Table 1 summarizes the 400 MHz 1H NMR chemical shifts
of the different groups observed in the spectra of three
copolymers of MATRIF. For example, the 1H NMR spectrum of
poly(AN-co-MATRIF) copolymer is given in Fig. 2.
The assignments were deduced from the comparison with
those of the homopolymers of cyano monomers [36,37] and
homopolymer and copolymers of MATRIF [22,24]. The spectra
showed the chemical shifts of different protons in the
copolymers. Peaks assigned to vinylic protons (5.6 and
Table 1
Assignments of 1H NMR chemical shifts /ppm for the copolymers of 2,2,2-trifluoromethacrylate (MATRIF)
Type of proton
Poly(AN-co-MATRIF)
Poly(MAN-co-MATRIF)
Poly(MVCN-co-MATRIF)
CH2 (main chain)
CH (AN)
1.5–2.4
2.6–3.2
1.7–2.4
–
1.5–2.5 (MATRIF)
–
CH3 (MATRIF)
CH3 (MVCN)
0.8–1.5
–
0.8–1.7
–
0.5–1.5
0.5–1.5
CH3 (MAN)
–
0.8–1.7
4.6
–
CH2CF3 (MATRIF)
4.6
4.6
CH (MVCN)
–
–
4.4–4.8

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M. Raihane, B. Ameduri / Journal of Fluorine Chemistry 127 (2006) 391–399
Fig. 2. 1H NMR spectrum of poly(AN-co-MATRIF) copolymer recorded in deuterated DMSO (DMSO-d6).
reactivity of AN toward MATRIF comonomer. The presence of
methyl in the main chain group in the MATRIF increases the
reactivity comparatively to the corresponding fluorinated
acrylate, MATRIF being considered as a captodative monomer
with a low donor effect arising from the methyl group. The
same conclusion can be proposed for the copolymer of MAN.
Table 2 shows also that the molar percentage of MVCN in the
copolymer is very low (5%). On the other hand, MVCN
monomer is less reactive towards the growing chain terminated
by MATRIF radicals. Due to the presence of the gem dicyano
groups, MVCN is an electron-deficient trisubstituted ethylene,
that copolymerizes easily with such electron-rich monomers as
substituted styrenes [5], vinyl acetate [11] and N-vinylpyrro-
lidone [40] to give high yields of high molecular weight
copolymers. However, it does not copolymerize with poor
electron monomers. As mentioned above, MATRIF is a
captodative monomer which bears, on the same carbon, a
strong electron-withdrawing group (CO2CH2CF3) and a low
donor group (CH3). Overall, this monomer can be qualified as a
poor electron inductive monomer. Hence, MVCN monomer
exhibits repulsive effects [9] when adding MATRIF comono-
mer and contains high proportions of MATRIF monomer
because MVCN does not homopolymerize giving trimer only.
The various resonances in 13C NMR spectra of copolymers
of MATRIF were assigned by comparing them with the spectra
of the homopolymers [24–37]. Table 3 summarizes the 13C
NMR chemical shifts of these copolymers and Fig. 3 shows the
13C NMR spectrum of poly(MAN-co-MATRIF) copolymer.
As the percentage of MVCN in the copolymer is low, the
spectrum of the poly(MVCN-co-MATRIF) copolymer is
similar to that of homopolymer of MATRIF [24]. The chemical
shifts of CH3, quaternary carbon C(CH3), CH2 (in the
backbone), and also C O, are very close to those of free
radical poly(methyl methacrylate), while the CF3 is effective on
the resonance of the carbon in the O–CH2 group which is
shifted to lower field [24]. The replacement of H-atom by CF3
group in MATRIF does not seem to affect the interactions
between incoming monomer and the last inserted monomer unit
Table 2
Percentage of MATRIF incorporated in various copolymers calculated from elemental analyses or 1H NMR
Copolymers
Elemental analyses
% of atom
13H NMR % molar (cyano monomer)
% molara (cyano monomer)
N (%)
O (%)
F (%)
Poly(AN-co-MATRIF)
Poly(MAN-co-MATRIF)
Poly(MVCN-co-MATRIF)
5.1
5.4
0.9
15.4
46.8
18.5
27.5
46.9
33
43.3
46.8
5.1
44.0
45.0
4.6
a
Values of the percentage of incorporated cyano monomer calculated from arithmetic mean of nitrogen, oxygen and fluor percentage.

M. Raihane, B. Ameduri / Journal of Fluorine Chemistry 127 (2006) 391–399
395
Table 3
Assignments of 13C NMR chemical shifts/ppm for the copolymers of MATRIF
Type of carbon
Poly(AN-co-MATRIF)
Poly(MAN-co-MATRIF)
Poly(MVCN-co-MATRIF)
CH2 (main chain)
32.5–37.0 (AN)
45.0–53.0
50.0–55.0
47.0–53.0 (MATRIF)
CH (AN or MVCN)
CH3 (MATRIF)
21.1–28.0
15.2–20.0
–
–
29.0–31.0
16.8–19.5
10.0
15.0–21.0
21.0–27.0
60.6–62.5
CH3 (MVCN or MAN)
CH2CF3 (MATRIF)
59.9–63.0
60.0–63.0
CO (MATRIF)
CN and CF3
172.9–176.0
117.9–131.0
172.5–176.0
116.0–130.0
174.6–178.0
116.0–130.0
C(CH3) (MAN, MATRIF)
C(CN)2 (MVCN)
42.5–46.0
44.5 (MATRIF)
44.7 (MATRIF)
30.7–32.3 (MAN)
38.0–40.0 (MVCN)
side chains in spite of the change of polarity involved [24]. The
triads concentration for syndiotactic (rr), heterotactic (mr) and
isotactic (mm) can be assessed from numerical integral of the
resonance from C O, I3, I4 and I5, respectively.
range 110–130 ppm (Fig. 3) shows five peaks: four signals
attributed to CF3 of MATRIF at 118, 122, 125 and 129 ppm, and
one peak at 124 ppm assigned to the resonance of CN of MAN
[39], with I6 and I7 integrals, respectively. The MAN molar
fraction in the poly(MAN-co-MATRIF) was calculated as
follows:
I3
rr ð%Þ ¼
ꢁ 100
(2)
I3 þ I4 þ I5
I7
MAN ðmol %Þ ¼
ꢁ 100
(3)
The expansion of the 166–183 ppm region assigned to the
carbonyl group in the 13C NMR spectrum of poly(MVCN-co-
MATRIF) copolymer (Fig. 4) gives 58% (rr), 37% (mr) and 5%
(mm).
By comparing the chemical shifts of the 13C NMR in
poly(MATRIF) with those of poly(MAN-co-para-methylstyr-
ene) copolymer [39], the expansion of the resonance of the CN
in the 13C NMR of poly(MAN-co-MATRIF) copolymer in the
I6 þ I7
The measurement of the corresponding integrals of two CN
groups gives 46% of MAN and 54% of MATRIF and is in good
agreement with the results of 1H NMR and elemental analyses
(Table 2). The expanded resonance of the carbonyl group of
poly(MAN-co-MATRIF) showed three broad peaks at 174, 175
and 175 ppm (Fig. 3) corresponding to MATRIF-centered
Fig. 3. 13C NMR spectrum of poly(MAN-co-MATRIF) copolymer recorded in deuterated DMSO (DMSO-d6).

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M. Raihane, B. Ameduri / Journal of Fluorine Chemistry 127 (2006) 391–399
Fig. 4. Expansion of the 166–183 ppm zone in the 13C NMR spectrum of poly(MVCN-co-MATRIF) copolymer.
triads MAN-MATRIF-MAN as it was observed in the
copolymers based on MAN and methyl a-acetoxylacrylate
[19,33] or MAN and a-cyano vinyl acetate [40]. These peaks
are not well separated compared with those of the alternating
copolymer. Therefore, poly(MAN-co-MATRIF) copolymer
could exhibit a statistical structure.
following equations, where Q1 and e1 represent the parameters
for cyano monomer while Q2 and e2 are those attributed to
MATRIF:
Q1
r1 ¼
exp½ꢀe1ðe1 ꢀ e2Þꢂ
(5)
(6)
Q2
For the poly(AN-co-MATRIF) copolymer, the percentage of
monomers incorporated was calculated by measuring the
integrals of signals in 13C NMR spectrum of methyl group of
MATRIF (I8) in the range 15–21 ppm and the CN and CF3
peaks (I9) in the 115–130 ppm range, using the relation below:
Q2
Q1
r2 ¼
exp½ꢀe2ðe2 ꢀ e1Þꢂ
The calculated values of the reactivity ratios and the product
(r1 ꢁ r2) are summarized in Table 4. The values of the product
(r1 ꢁ r2) for poly(AN-co-MATRIF) and poly(MAN-co-
MATRIF) copolymers are close to 1, explaining the statistical
structures. This result is in good agreement with the NMR
characterization above. The reactivity ratio of MVCN is close
to zero and means that MVCN does not homopolymerize. The
reactivity ratio of MATRIF is rather high (r2 = 32.5) compared
to some comonomers of MVCN such as vinyl acetate
(r2 = 0.07) or p-chlorostyrene (r2 = 0.78) [45]. As r2 constant
is defined as the ratio between the homopolymerization rate
constant of MATRIF (k22) and the propagation rate of MATRIF
radical onto MVCN monomer (k21), the higher value of r2
indicates that the probability of homopolymerization of
MATRIF is quite high. This result explains the low percentage
I9 ꢀ I8
AN mol % ¼
ꢁ 100
(4)
I9
The copolymer contains approximately a 42:58 mol ratio of
AN:MATRIF in good agreement with the elemental analyses
(Table 2). In the alternating copolymers of poly(VCN-alt-
methyl a-acetoxylacrylate) [13,33] and poly(VCN-alt-methyl
methacrylate) copolymers [41], the resonance of carbonyl
carbon shows three peaks in 0.25:0.50:0.25 ratio arising from
the triad sequences centered in methyl a-acetoxylacrylate. The
expansion of the C O band in poly(AN-co-MATRIF)
copolymer in the range 172–176 ppm shows four multiplets
centred at 173, 174, 175 and 175 ppm confirming the statistical
structure of this copolymer, as it was observed in poly(AN-co-
methyl a-acetoxyacrylate) copolymer [19].
Table 4
The results of the Alfrey–Price Q–e parameters [42] where
Q and e take into account the stabilization by resonance and the
polar effects of the monomer are commonly used to predict the
monomer reactivity ratios. The Alfrey–Price parameters are
known for AN (Q1 = 0.48, e1 = 1.24) [43], MAN (Q1 = 0.85,
e1 = 0.79) [43], MVCN (Q1 = 0.2, e1 = 2.766) [44] and
MATRIF (Q2 = 1.13, e2 = 0.98) [27]. The values of r1 of cyano
monomers and r2 of MATRIF were determinated from the
Reactivity ratios of cyano monomers (r1) and MATRIF (r2) and the values of the
product (r1 ꢁ r2) calculated from the Alfrey–Price parameters
Copolymers
r1
r2
r1 ꢁ r2
Poly(AN-co-MATRIF)
Poly(MAN-co-MATRIF)
0.31
0.87
3.04
0.93
0.96
1.10
Poly(MVCN-co-MATRIF)
0
32.52
0
ri represents the ratio of the homopropagation rate to the crosspropagation rate.

M. Raihane, B. Ameduri / Journal of Fluorine Chemistry 127 (2006) 391–399
397
Table 5
Average molecular weight, Mn, and Mw, and polydispersity indices (PDI)
Copolymers
Mn
Mw
PDI
Poly(AN-co-MATRIF)
Poly(MAN-co-MATRIF)
24000
14000
38000
24000
1.58
1.71
Poly(MVCN-co-MATRIF)
13000
22000
1.69
Mn and Mw represent the average molecular weights in number and in weight of
the copolymer, respectively.
of incorporation of MVCN in the poly(MVCN-co-MATRIF)
copolymer (5%) calculated from elemental analyses and NMR
characterization.
Fig. 5. TGA thermograms under nitrogen of copolymers of MATRIF: (a)
poly(AN-co-MATRIF), (b) poly(MAN-co-MATRIF) and (c) poly(MVCN-co-
MATRIF).
Table 5 shows also the average molecular weights, Mn and
Mw, and polydispersity indices (PDI). The values of the PDI are
in the range 1.58–1.71 corresponding to the radical polymer-
ization without any transfer reaction.
and marked inhibition or rotation about C–C bonds. The
presence of strong CN dipoles in the backbone increases the
interaction between the chains [46]. The low Tg value in the
poly(MVCN-co-MATRIF) copolymer arises from the low
incorporation of MVCN which reduces the interaction
between the main chains.
2.3. Thermal properties of the copolymers
Two key thermal properties were studied, glass transition
temperature, Tg, and thermal degradation, Td, determined by
differential scanning calorimetry (DSC) and by thermogravi-
metry analysis (TGA), respectively.
The thermal degradation of three copolymers, poly(AN-co-
MATRIF), poly(MAN-co-MATRIF) and poly(MVCN-co-
MATRIF) copolymers, was studied by means of thermogra-
vimetry. Table 6 lists their temperatures when the copolymers
start to decompose and their degradation temperature
corresponding to 10% of weight loss. Thermogravimetric
analyses showed that thermal decomposition occurred from
200, 230 and 240 8C for copolymers containing MVCN, MAN
and AN, respectively (Fig. 5). TGA thermograms of these
fluoropolymers indicated that the process of degradation
depends on the nature of the cyano monomer as it was
observed in AN or MAN with methyl a-acetoxylacrylate
copolymers [46].
First, all the copolymers analyzed show a sharp transition
from the glassy domain to the viscoelastic one, as evidenced
by the presence of only a neat Tg [28]. Although DSC was
also realized on all samples from 25 to 180 8C, the absence of
any crystallization or melting temperature was noted. The Tg
range, between 77 and 86 8C (Table 6), indicates that the
copolymer exhibited amorphous behavior. As expected, the
Tgs of copolymers of MAN were higher than those of the
copolymers of AN (the replacement of the H-bond by a
methyl group increasing the Tg due to steric effect of CH3).
This result is in good agreement with the Tgs of the
copolymers of vinyl acetate (VAc) with AN and MAN
since the corresponding Tgs were 86 and 102 8C, respectively
[10].
3. Conclusion
Copolymers containing 2,2,2-trifluoroethyl methacrylate
and cyano monomers (AN, MAN and MVCN) were
synthesized by radical copolymerization initiated by AIBN.
These copolymers were characterized by 1H, 19F and 13C NMR
as well as FT-IR spectroscopies. The copolymer compositions
were determined by NMR spectroscopy and elemental
analyses. The molar percentages of incorporation of AN and
MAN were 44 and 45%, respectively. However, only 5%
MVCN was incorporated in MVCN with MATRIF copolymer.
The values of the product (r1 ꢁ r2) calculated from Alfrey–
Price Q–e parameters were 0.93 and 0.96 for poly(AN-co-
MATRIF) and poly(MAN-co-MATRIF) copolymers, respec-
tively, which explain the statistical structures of these
copolymers. The calculated values of the reactivity ratios of
MVCN (r1 = 0) and of MATRIF (r2 = 32.52) explain the low
reactivity of MVCN towards the MATRIF radicals in
poly(MVCN-co-MATRIF) copolymer. DSC and TGA showed
that the copolymers were amorphous and stable up to 200, 230
and 240 8C for copolymers of MVCN, AN and MAN,
respectively.
Generally, the copolymers of MVCN exhibit high Tg when
those of poly(MVCN-alt-VAc) (172 8C) [11], poly(MVCN-
alt-styrene) (Tg = 167 8C) [40] or poly(MVCN-alt-vinylpyr-
rolidone) (Tg = 210 8C) copolymers [40] are considered. The
incorporation of polar cyano groups in the copolymer
backbone resulted in an increase of Tg due to chain stiffening
Table 6
Glass transition and decomposition temperatures of poly(M-co-MATRIF)
copolymers
Copolymer
Tg (8C)
Td (8C)a
Td0 (8C)b
Poly(AN-co-MATRIF)
Poly(MAN-co-MATRIF)
Poly(MVCN-co-MATRIF)
77
86
69
240
230
200
345
264
221
a
Td: temperature of beginning of degradation; copolymers heated under
nitrogen at 10 8C minꢀ1
.
b
Td0 : temperature of degradation at 10% of loss weight; copolymers heated
under nitrogen at 10 8C minꢀ1
.

398
M. Raihane, B. Ameduri / Journal of Fluorine Chemistry 127 (2006) 391–399
4. Experimental
Infrared spectroscopy measurements were performed in
transmittance with a spectrometer Nicolet 510 P. The accuracy
4.1. Materials
was ꢃ2 cmꢀ1
.
Differential scanning calorimetry measurements were
conducted using a Perkin-Elmer Pyris 1 instrument connected
to a micro-computer. The apparatus was calibrated with indium
and n-decane. After its insertion into the DSC apparatus, the
sample was cooled initially to ꢀ100 8C for 15 min. Then, the
first scan was made at a heating rate of 20 8C minꢀ1 up to
100 8C, where it remained for 2 min. It was then cooled to
ꢀ100 8C at the rate of 320 8C minꢀ1 and left for 10 min at that
temperature before a second scan was started at a heating rate of
20 8C minꢀ1, giving the values of Tg reported herein, taken at
the half-height of the capacity jump of the glass transition.
Thermogravimetry analyses were performed with a Texas
Instrument TGA 51-133 apparatus in nitrogen at a heating rate
of 10 8C minꢀ1 from room temperature up to 500 8C.
Gel permeation chromatography (GPC) or size exclusion
chromatography (SEC) was carried out in tetrahydrofuran at
30 8C, at a flow of 0.8 ml minꢀ1, by means of spectra Physics
Winner Station, a Waters Associate R 401 differential
refractometer and a set of four columns connected in series:
Styragel (Waters) HR4 5m, HR3 analyses, PL Gel (Polymer
Laboratories) 5m, 100 A. Poly(methyl methacrylate) mono-
dispersed standards were used for calibration. Aliquots were
sampled from the reaction medium, diluted with tetrahydro-
furan up to a known concentration (Cp,t) (ca. 4 wt.%), filtered
through a 20 mm PTFE Chromafil membrane and finally
analyzed by GPC under the conditions described above.
Methacrylonitrile and acrylonitrile are commercial pro-
ducts (Aldrich Chimie, 38299 St. Quentin, Fallavier, France)
and were distilled under reduced pressure, then stored below
5 8C prior to use. a,a0-Azobisisobutyronitrile (AIBN) was
provided by Aldrich and was purified by recrystallization in
ethanol. Acetonitrile of analytical grade (Aldrich) was
distilled over calcium hydride prior to use. Methylvinylidene
cyanide was synthesized from acetaldehyde and malononitrile
in presence of b-alanine as a base (the details of the procedure
for the preparation of MVCN were reported elsewhere
[34,35]). 2,2,2-Trifluoroethyl methacrylate was used as
fluorinated comonomer, kindly offered by Atofina (now
Arkema), France, and was distilled prior to use in the reaction
mixture.
4.2. Synthesis of copolymers
The radical copolymerization of cyano monomers (AN,
MAN or MVCN) with MATRIF were performed in thick
borosilicate Carius tubes (length 130 mm, internal diameter
10 mm, thickness 2.5 mm, total volume 8 cm3). After introdu-
cing initiator (AIBN, 1 wt.% relative for the monomer
mixture), cyano monomer, MATRIF and acetonitrile under
inert atmosphere, the tube was connected to a vacuum line and
purged several times by evacuating and flushing with helium.
After six thaw–freeze cycles to remove oxygen, the tube was
cooled into liquid nitrogen, sealed under vacuum and placed
into a shaking oven heated at 80 8C for 12 h. After reaction, the
tube was cooled into liquid nitrogen, opened and the total
product mixture was solubilized in dimethyl formamide,
chloroform or tetrahydrofuran and then precipitated from
methanol or pentane. The copolymer formed was isolated by
filtration and dried under vacuum at 80 8C. These copolymers
Acknowledgements
The authors thank the Agence Universitaire de la
Francophonie (project AUF: 6301PS336), the CNRST (Mor-
occo)–CNRS (France) programme (Chimie 07/05/No. 17691)
and PROTARS III (D13/16), for their financial supports.
1
were characterized by H, 13C and 19F NMR, IR, DSC, TGA,
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