Perfluoro-4-methyl-1,3-dioxole: A new monomer for high-Tg amorphous fluoropolymers

Article abstract of DOI:10.1016/j.jfluchem.2003.10.009

A 4-Chloro-5-trifluoromethyl-2,2,4-trifluoro-1,3-dioxolane (1) was synthesised by reaction of CF₂(OF)₂ with CF₃-CH=CFCl; the elimination of HCl from (1) in basic conditions led to the formation of dioxole perfluoro-4-methyl-1, 3-dioxole (2). Both these synthetic steps gave the corresponding product in high yield. A new synthetic route for the preparation of CF₃-CH=CFCl, starting from CF₂ClBr and CH₂=CF₂, together with some examples of polymerisation products obtained by reaction of dioxole (2) with fluoroolefins are also reported.

Full text of DOI:10.1016/j.jfluchem.2003.10.009

Journal of Fluorine Chemistry 125 (2004) 73–78
Perfluoro-4-methyl-1,3-dioxole: a new monomer for
high-T amorphous fluoropolymers
g
*
Antonio Russo , Walter Navarrini
Solvay Solexis, R & D Centre, V.le Lombardia 20, 20021 Bollate (MI), Italy
Received 15 October 2003; received in revised form 15 October 2003; accepted 23 October 2003
Abstract
A 4-Chloro-5-trifluoromethyl-2,2,4-trifluoro-1,3-dioxolane (1) was synthesised by reaction of CF (OF) with CF –CH¼CFCl; the
2
2
3
elimination of HCl from (1) in basic conditions led to the formation of dioxole perfluoro-4-methyl-1,3-dioxole (2). Both these synthetic
steps gave the corresponding product in high yield.
A new synthetic route for the preparation of CF –CH¼CFCl, starting from CF ClBr and CH ¼CF , together with some examples of
3
2
2
2
polymerisation products obtained by reaction of dioxole (2) with fluoroolefins are also reported.
#
2003 Elsevier B.V. All rights reserved.
Keywords: Bis(fluoroxy)difluoromethane; Reactivity; Synthesis; Chlorofluoro propenes; Isomerization; Dioxolanes; Perfluorodioxoles
1
. Introduction
separation membranes, advanced electronic, optical, and
biomedical applications. In the light of these considerations,
new fluorodioxoles and new synthetic methods for their
preparation have received particular attention.
The low temperature reaction of CF (OF) with alkenes
2
2
was found to lead to the formation of 2,2-difluoro-1,3-
dioxolanes (Eq. (1)) [1,2], as well as to linear haloethers
depending on the reaction conditions adopted [4]. These
intermediates are useful for the preparation of sophisticated
perfluoro monomers, which are building blocks for the
industrial synthesis of amorphous perfluoropolymers having
In the literature, halogenated 2,2-difluoro-1,3-dioxolanes
have been prepared using multistep processes often with low
or inconsistent yields [5]. As an alternative, the chemistry of
CF (OF) provides a direct and versatile way to obtain
2
2
dioxolane rings [2].
Herein, we report the synthesis of 4-chloro-5-trifluoro-
methyl-2,2,4-trifluoro-1,3-dioxolane (1) and perfluoro-4-
T s within the exceptionally wide range of þ300 to À70 8C
g
[
3–7].
Eq.(1)
Perfluorodioxoles based polymers are similar to poly(te-
methyl-1,3-dioxole (2) together with some examples of
the polymeric materials obtained from dioxole (2) and
fluoroolefins.
trafluoroethylene) in their chemical and thermal stability, but
they have enhanced physical and mechanical properties,
better optical clarity, and lower dielectric constants. In
addition, these polymers may be soluble in selected fluori-
nated solvents. These unique characteristics make fluoro-
dioxole containing polymers good candidates for gas
*
Corresponding author. Tel.: þ39-023-8356400;
fax: þ39-023-8356355.
E-mail address: antonio.russo@solvay.com (A. Russo).
0022-1139/$ – see front matter # 2003 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2003.10.009

74
A. Russo, W. Navarrini / Journal of Fluorine Chemistry 125 (2004) 73–78
2
. Results and discussion
Since the starting olefin 3 had a trans/cis ratio equal to
/4 this result indicates that the reaction which leads to
6
Dioxolane 1 and dioxole 2 were prepared, in high yield, as
shown below:
the formation of the dioxolane ring, may be faster than the
rotation of the radical intermediate (Scheme 1). This sug-
gestion seems to be in contrast with an earlier finding that the
syn/anti geometry of the dioxolane products is independent
of the starting olefin [2]. This paradox may be explained by
the higher rotation barrier energy of the radical intermediate
in the present case due to the bulkier CF group as compared
3
with hydrogen and chlorine.
In fact, the anti configuration of the dioxolane ring should
be preferred because of the steric hindrance between the CF3
group and the chlorine atom, therefore the syn olefin should
lead to the anti isomer as the major product, resulting in a
larger amount of the anti isomer among the reaction pro-
ducts.
Eq.(2)
Eq.(3)
In order to prepare dioxoles from dioxolanes a general
method of synthesis reported in the chemical literature con-
sists of a dehalogenation reaction, usually dechlorination, of a
dioxolane ring in which one chlorine atom is present at the
4-position and one at the 5-position of the ring. The dehalo-
genation reactions are usually carried out with a metal (Zn,
Mg) in polar aprotic solvents (in particular DMF and DMSO).
Such dehalogenation constitutes a problem in the per-
fluorodioxole synthesis, because it usually gives low yields.
The first step of the synthesis (Eq. (2)) leads to the
formation of the 4-chloro-5-trifluoromethyl-2,2,4-trifluoro-
1,3-dioxolane 1 both in the anti isomer 1a (in which the CF3
group and the chlorine atom are in anti position) and in the
syn isomer 1b (in which the CF group and the chlorine atom
3
are in syn position) with an isomer ratio anti=syn ¼ 6=4.
Scheme 1.

A. Russo, W. Navarrini / Journal of Fluorine Chemistry 125 (2004) 73–78
75
Scheme 2.
AlCl3
Generally the dehalogenation yield increases if, in the
starting dioxolane, the relative amount of the anti isomer
5
! CF3ÀCH¼CFCl
Eq.(6)
ð3Þ
(
in which the two chlorine atoms are anti) is higher than that
of the syn isomer (in which the two chlorine atoms are syn)
8].
In this work, the substituents at the 4- and 5-positions of
A 1-Bromo-3-chloro-1,1,3,3-tetrafluoropropane (4) was
[
prepared, in 62% yield, by a peroxide-initiated reaction of
bromochlorodifluoromethane with vinylidene fluoride at
110 8C (Eq. (4)).
Dehydrohalogenation of 4 in phase transfer conditions
gave, selectively, 3-chloro-1,1,3,3-tetrafluoropropene (5) in
84% yield. In this case also the dehydrohalogenation reac-
tion could lead to elimination of HCl in place of HBr but it
was totally selective toward HBr elimination suggesting an
E2 type mechanism [9].
the dioxolane have been properly chosen in order to obtain
the dioxole 2 by a dehydrochlorination reaction (Eq. (3)) in
place of the generally used dehalogenation reaction. This
reaction was carried out with NaOH or KOH aqueous
solutions under phase transfer conditions. Both the anti
isomer 1a and the syn isomer 1b gave the dioxole product
2
in good yield. The mechanism that leads to the product
could be different for the two isomers. It seems likely that an
E2 elimination should be favoured for the syn isomer 1b in
which the hydrogen atom and the chlorine atom are anti to
one another, while for the anti isomer 1a it seems more
likely that the reaction proceeds through an E1cB mechan-
ism (Scheme 2).
It should be noted that even if the dehydrohalogenation
reaction could also lead to elimination of HF in place of HCl,
in our experiments the reaction was totally selective toward
the HCl elimination.
Compound 5 isomerised in 85% yield to a mixture (6:4) of
trans- and cis-1-chloro-1,3,3,3-tetrafluoropropene (3) when
treated with catalytic amount of AlCl (Eq. (6)). The iso-
merization process likely involves an allylic cation as shown
in Scheme 3.
As reported above, perfluorodioxoles are of interest as
monomers in the preparation of fluoropolymers especially in
the preparation of copolymers with tetrafluoroethylene
(TFE). It has been reported by Hung that the steric bulkiness
of the substituents in the 4- and 5-positions of the dioxole
ring is critical for the polymerisation reaction rate [4].
Furthermore Hung reported that perfluoro-2,2,4-trimethyl-
3
The starting olefin CF –CH¼CFCl (3) was prepared by a
3
three-step original approach (Eqs. (4)-(6)):
1
,3-dioxole (6) failed to copolymerise with TFE. It seems
ðtBuOÞ2
that the low reactivity in the polymerisation reactions of 6 is
due to the steric effect of the trifluoromethyl group at the
4-position. This conclusion may be reasonable if we con-
sider that perfluoro-2,2-dimethyl-1,3-dioxole (7), in which
CF2BrCl þ CH2¼CF2 ! CF2BrÀCH2ÀCF2Cl
Eq.(4)
Eq.(5)
ꢀ
1
20 C
ð4Þ
KOH
! CF2¼CHÀCF2Cl
4
PTC
ð5Þ
the CF group at 4-position in 6 is replaced by a fluorine
3

76
A. Russo, W. Navarrini / Journal of Fluorine Chemistry 125 (2004) 73–78
Scheme 3.
atom, is very reactive and it has also a tendency to homo-
polymerize even at a temperature as low as À78 8C.
with glass/PTFE or stainless-steel valves. Pressures were
measured with a Druck PDCR 110/W differential pressure
gauge. Quantities of gaseous reactants and products
were measured from measured volumes assuming ideal
gas behaviour.
1
9
1
F NMR and H NMR spectra were recorded on Varian
00 MHz and Varian 300 MHz instruments respectively
2
with CDCl3 as solvent and CFCl3 or TMS as internal
standards. GLC analyses were performed with a HRGC
In contrast to dioxole 6, the new dioxole 2 undergoes
copolymerisationwithTFE(CF ¼CF )andVDF(CF ¼CH )
5
300 Carlo Erba instrument equipped with thermal con-
2
2
2
2
ductivity detectors. Glc/ms spectra were performed on a
Varian Mat CH7-A at 70 eV in the electron impact mode.
Materials: Chemicals were obtained from commercial
sources and directly utilized.
leading to the formation of novel copolymers comprising the
new following units in the polymer chains [10].
Bis(fluoroxy)difluoromethane was prepared according to
the standard methods described in the literature [12–15].
Caution!! Appropriate precautions should be taken
when handling hypofluorites [1]. Under certain condi-
tions, these compounds are capable of an energetic
explosive decomposition.
This monomer failed to homopolymerizewhen initiated by
perfluoropropionyl peroxide or AIBN in pure liquid dioxole.
This tendency can also be seen in the copolymerization with
TFE (3.6.) and VDF (3.7), where the dioxole incorporated in
the polymer obtained is lower than 51% despite the high
dioxole and low TFE or VDF concentrations [10].
3.1. Preparation of 1-bromo-3-chloro-1,1,3,
3-tetrafluoropropane (4)
A 370 ml stainless steel reactor, equipped with a mag-
netic entrainment mechanical stirrer, was charged with
CF BrCl (280 g, 1.7 mol) and tert-butyl peroxide (2.8 g,
2
In conclusion, two new compounds belonging to the
family of 2,2-difluoro-1,3-dioxolanes and 1,2,3-trifluoro-
0.02 mol). The reactor was then heated to 110 8C and fed
for eight h with vinylidene fluoride (VDF) keeping the
pressure inside the reactor between 15 and 20 atm. At
the end of the reaction, 65 g (1.01 mol) of VDF had been
fed. The reaction mixture was fractionally distilled to
afford 145 g (0.63 mol) of 4 as a clear, colourless liquid.
The yield of the reaction was 62%. Compound 4 has
b.p. 85 8C.
4
-perfluoroalkyl-1,3-dioxoles have been synthesised. An
alternative synthesis of perfluoro-1,3-dioxoles from 1,3-diox-
olanes has been reported in which a dehydrohalogenation
reaction has been used in place of the generally used deha-
logenation reaction. Although the olefin CF –CH¼CFCl is
3
a known compound [11], a new process for its synthesis is
also reported.
1
9
BrCF –CH –CF Cl: F NMR: dA ¼ À41:9 ppm (2F, tt);
2
2
2
Finally, the successful polymerisation reaction of 2 with
TFE and VDF provides the possibility to obtain new fluori-
nated polymers, which may lead to valuable potential appli-
cations.
dB ¼ À46:6 ppm (2F, tt).
1
H NMR: 3.2 ppm (2H, tt). JAB ¼ 12 Hz; JAH ¼
JBH ¼ 12 Hz.
þ
þ
MS (EI) (m/z, [fragment]): 195 [M–Cl ]; 149 [M–Br ],
þ þ
00%; 129 [CF Br ]; 85 [CF Cl ].
2 2
1
À1
3
. Experimental
IR (cm ): 2980, 1364, 1218, 1182, 1148, 938, 800, 692,
42, 566.
Analysis: calc. for C H F BrCl: C, 15.69; F, 33.13%.
6
General methods: Volatile compounds were handled in
a glass and/or stainless-steel vacuum system equipped
3
2 4
Found: C, 16.08; F, 32.93%.

A. Russo, W. Navarrini / Journal of Fluorine Chemistry 125 (2004) 73–78
77
3
.2. Preparation of 3-chloro-1,1,3,3-tetrafluoropropene
Analysis: calc. for C HF Cl: C, 24.2; F, 51.2%. Found: C,
3 4
(
5)
24.0; F, 50.6%.
Compound 4 (25 g, 0.11 mol) obtained as above was
mixed with (Bu) NOH (1.5 g) (40% (w/w) aqueous
3.4. Preparation of 4-chloro-5-triluoromethyl-2,2,
4-trifluoro-1,3-dioxolane (1)
4
solution) in a reaction flask fitted with a dropping funnel,
a magnetic stirrer, and a water-cooled condenser con-
nected, via a trap cooled to À78 8C, to a vacuum system
that was used to maintain a pressure of ca. 400 mm
Hg.
The reaction mixture was heated to 45 8C and KOH
aqueous solution (25 ml, 30% (w/w)) was added dropwise
under vigorous stirring. At the end of the addition, the
pressure was lowered to 200 mmHg and the reaction pro-
ducts, collected in the cold trap, were fractionally distilled to
give the alkene 5 as a clear, colourless liquid, yield: 13.7 g
In a 200 ml multi-necked cylindrical glass reactor
equipped with mechanical stirrer, thermocouple, dipping
inlet for the reaction gaseous mixture, outlet with inert gas
flow, 51.3 g (0.346 mol) of 3 were introduced. The reactor
was then brought by means of a cryostat to À70 8C and,
under mechanical stirring, a mixture of CF (OF) (1 l/h) and
2 2
helium (3 l/h) was continuously fed for 1.9 h. The reaction
products were separated by fractional distillation to give
28.9 g of 1 as a mixture (4/6 by 19F and H NMR spectro-
1
scopy) of syn- and anti-isomers, yield (based on CF
72.8%. Compound 1 has b.p. 56 8C.
(OF) ):
2
2
(
83%). Compound 5 has b.p. 14 8C.
19
19
ClCF –CH¼CF : F NMR: d ¼ À51:0 ppm (2F, ddd);
: syn-isomer: F NMR: dA ¼ À75:8
2
2
A
1
1
d ¼ À71:6 (1F, ddt); d ¼ À78:5 (1F, ddt). H NMR:
ppm (3F,); dB ¼ À47:8 ppm (1F,). H NMR: 5.05 ppm
B
C
d ¼ 5:05 (1H, dtd). JAB ¼ 21 Hz; JAC ¼ 9 Hz; JAH ¼
(1H,).
anti-isomer: 19F NMR: dA ¼ À75 ppm (3F, dd);
9
Hz; JBC ¼ 9 Hz; JBH ¼ 22 Hz; JCH ¼ 1:5 Hz.
þ
þ
1
MS (EI) (m/z, [fragment]): 148 [M ]; 129 [M-F ]; 113
M-Cl ], 100%; 85 [CF Cl ]; 63 [C F H ].
dB ¼ À68:3 ppm (1F,). H NMR: 5.12 ppm (1H,).
þ
þ
þ
þ
[
MS (EI) (m/z, [fragment]) (isomer mixture): 195 [M-Cl ];
2
2 2
À1
þ þ þ
F HO ], 100%; 161 [M-CF ]; 148 [C F HO ];
3 6 3 3 5
IR (cm ): 3144, 3098, 1758, 1372, 1269, 1227, 1098,
008, 935, 831, 792, 580.
Analysis: calc. for C HF Cl: C, 24.2; F, 51.2%. Found: C,
167 [C
101 [C
þ
þ
1
2
3
2
F
4
À1
H ]; 69 [CF
3
].
IR (cm ) (isomers mixture): 2998, 1383, 1307, 1279,
1194, 1116, 1078, 989, 921, 840, 707.
Analysis: calc. for C HF O Cl: C, 20.8; F, 49.5%. Found:
3
4
4.5; F, 50.0%.
4
6 2
.3. Preparation of 1-chloro-1,3,3,3-tetrafluoropropene,
C, 20.4; F, 49.3%.
(
3)
3.5. Preparation of perfluoro-4-methyl-1,3-dioxole (2)
AlCl (1 g, 0.007 mol) was added under stirring to 5 at
3
Compound 1 obtained as above (9 g, 0.039 mol) was
mixed with 1.5 g of (Bu) NOH (40% (w/w) aqueous solu-
À30 8C, in a flask (50 ml) fitted with a nitrogen inlet and
a water-cooled reflux condenser connected, via a trap
cooled to À196 8C, to a vacuum system. The reaction
mixture was allowed to warm slowly up to 13 8C while a
slow stream of nitrogen was passed through the apparatus
during this period. The flow of nitrogen was then inter-
rupted and the reaction products pumped off through
the cold trap at 400 mm Hg. The products collected in
the cold trap were then fractionally distilled to give com-
4
tion) in a reaction flask (50 ml) fitted with a dropping funnel,
a magnetic stirrer, and a water-cooled condenser connected,
via a trap cooled to À196 8C, to a vacuum system that was
used to maintain a pressure of ca. 400 mmHg. The reaction
mixture was kept at room temperature while of KOH aqu-
eous solution (25 ml, 30% (w/w)) was added drop wise
under vigorous stirring. At the end of the addition of the
KOH solution, the pressure was lowered to 60 mmHg
and the reaction products, collected in the cold trap,
were fractionally distilled to give 4.5 g (yield: 61.3%) of
the dioxole 2 as a clear, colourless liquid and 2.19 g of the
starting dioxolane 1. The conversion of the reaction
was 84.3% and the selectivity 72.7%. Compound 2 has
b.p. 14–15 8C.
pound 3 as a mixture (6/4) by 1 F and H NMR spectro-
9
1
scopy of trans- and cis-1-chloro-1,3,3,3-tetrafluoropropene
(
13.6 g, 0.092 mol). Yield ¼ 84%. Compound 3 has
b.p. 17 8C.
1
9
CF –CH¼CFCl: cis-isomer F NMR: dA ¼ À59:1 ppm
3
1
(
3F, dd); dB ¼ À62 ppm (1F, qd). H NMR: 5.78 ppm (1H,
qd). JAB ¼ 14 Hz; JAH ¼ 6 Hz; JBH ¼ 8 Hz.
1
9
: 19F NMR: d ¼ À65:8 (3F,
trans-isomer: F NMR: dA ¼ À59:2 ppm (3F, dd);
A
1
dB ¼ À60:7 ppm (1F, qd). H NMR: 5.38 ppm (1H, qd).
d); d ¼ À130:4 (1F, q); d ¼ À47 (2F, s). J ¼ 11 Hz.
B
C
AB
þ þ
J
¼ 17 Hz; J ¼ 7 Hz; J ¼ 25 Hz.
MS (EI) (m/z, [fragment]): 194 [M ], 100%; 175 [M-F ];
147 [C F O ]; 97 [C F Oþ]; 69 [CF ].
AB
AH
BH
þ
þ
À1
þ
MS (EI) (m/z, [fragment]) (isomers mixture): 148 [M ];
29 [M-Cl ], 100%; 69 [CF3 ].
3
5
2
3
3
þ
þ
1
IR (cm ): 1802, 1435, 1345, 1294, 1223, 1208, 1194,
1180, 1115, 1029, 992, 727, 491.
Analysis: calc. for C F O : C, 24.7; F, 58.8%. Found: C,
À1
IR (cm
691 (trans), 1353, 1268, 1197, 1165, 1110, 1062, 859,
72.
) (isomers mixture): 3127, 1748 (cis),
1
6
4
6 2
24.6; F, 58.1%.

78
A. Russo, W. Navarrini / Journal of Fluorine Chemistry 125 (2004) 73–78
3
3
.6. Amorphous copolymer of perfluoro-4-methyl-1,
-dioxole with TFE
was brought to À196 8C and evacuated, warmed to room
temperature, cooled again to À196 8C and evacuated. The
freezing and warming procedure was repeated twice; at the
end of the degassing operations the reactor was brought
to 30 8C and maintained at this temperature for 4 h under
magnetic stirring. The reactor was then cooled to À196 8C,
In a 50 ml steel reactor with magnetic stirrer and inlet for
the reactant feeding and discharge, 1 ml of perfluoropropio-
nyl peroxide at 6% by weight in CCl FCClF , 6.5 mmols
2
2
À3
of perfluoro-4-methyl-1,3-dioxole (PMD) and 10 mmol
of uninhibited tetrafluoroethylene were introduced. The
charged reactor was brought to À196 8C and evacuated,
warmed to room temperature, cooled again to À196 8C and
evacuated. The freezing and warming procedure was
repeated twice; at the end of the degassing operations the
reactor was brought to 30 8C and maintained at this tem-
perature for 8 h under magnetic stirring. The reactor was
then cooled to À196 8C, connected to a vacuum system at a
connected to a vacuum system at a pressure of 10 mbar,
and allowed to reach room temperature while fractionating
the vapours by traps cooled at À80, À120, and À196 8C.
After solvent and unreacted monomers distillation and
subsequent stripping of the polymer under vacuum at the
temperature of 130 8C for 3 h, 175 mg of polymer were
isolated. The mass balance of the unreacted monomers
determined by g.l.c. indicated that the PMD percentage
molar in the polymer was 50%. The polymer T , determined
g
À3
pressure of 10 mbar, and allowed to reach room tempera-
by DSC, was 60.9 8C; the DSC analysis did not show any
residual crystallinity. The TGA showed a weight loss of 10%
at 301 8C.
ture while fractionating the vapours by traps cooled at À80,
À120 and À196 8C. At the end of the fractionation, the trap
at À80 8C contained CCl FCF Cl only, the trap at À120 8C
2
2
contained 1.18 mmol of CCl FCF Cl and 6.1 mmol of
2
2
References
unreacted dioxole and the trap at À196 8C contained
9.57 mmol of unreacted TFE. After solvent and unreacted
monomers distillation and subsequent stripping of the poly-
[
1] W. Navarrini, V. Tortelli, A. Russo, S. Corti, J. Fluorine Chem. 95
1999) 27–39.
(
mer under vacuum at the temperature of 130 8C for 3 h,
[2] W. Navarrini, L. Bragante, S. Fontana, V. Tortelli, A. Zedda, J.
Fluorine Chem. 71 (1995) 111–117.
4
0 mg of polymer were isolated. The mass balance of the
[
[
3] W. Navarrini, S. Corti, J. Fluorine Chem. Special issue: ‘‘Fluorine
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unreacted monomers determined by g.l.c. indicated that the
PMD percentage molar in the polymer was 48%. The
4] M.-H. Hung, Macromol. 26 (1993) 5829.
polymer T , determined by DSC, was 165 8C; the DSC
g
[5] E.N. Squire, US Patent 4,399,264 (1983).
analysis did not show any residual crystallinity. The TGA
showed a weight loss of 10% at 327 8C.
[6] B.E. Smart, A.E. Feiring, C.G. Krespan, Z.Y. Yang, M.H. Hung, P.R.
Resnik, Macromol. Symp. 98 (1995) 753–767.
[
7] W. Navarrini, V. Tortelli, P. Colaianna, J.A. Abusleme, US Patent
,646,223 (1997).
5
3
3
.7. Amorphous copolymer of perfluoro-4-methyl-1,
-dioxole with VDF
[
[
8] W. Navarrini, S. Fontana, US Patent 5,296,617 (1994).
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[
[
[
[
[
10] A. Russo, W. Navarrini, US Patent 6,469,185 (2002).
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14] P.G. Thompson, J. Am. Chem. Soc. 89 (1967) 1811.
In a 50 ml steel reactor with magnetic stirrer and inlet for
the reactant feeding and discharge, 80 ml of perfluoropro-
pionyl peroxide at 6% by weight in CCl FCClF and
2
2
5 mmols of perfluoro-4-methyl-1,3-dioxole and 10 mmol
of uninhibited VDF were introduced. The charged reactor
[15] M.J. Fifolt, US Patent 4,499,024 (1985).