1070-4272/01/7410-1740 $25.00 C 2001 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 74, No. 10, 2001, pp. 1740!1743. Translated from Zhurnal Prikladnoi Khimii, Vol. 74, No. 10, 2001,
Original Russian Text Copyright + 2001 by Kiryukhin, Barkalov, Ismoilov.
AND POLYMERIC MATERIALS
Cryoozonolysis of Some Perfluoroolefins
and Use of Perfluoro Ozonides as Polymerization Initiators
D. P. Kiryukhin, I. M. Barkalov, and I. L. Ismoilov
Institute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka, Moscow oblast, Russia
Received May 7, 2001
Abstract-Low-temperature (773280 K) ozonolysis of perfluoro-4-methyl-2-pentene and perfluoro-2,4-di-
methyl-3-ethyl-2-pentene by direct contact with ozone in the absence of solvents and oxygen was studied. The
resulting perfluoro ozonides can be used as initiators of low-temperature polymerization and copolymerization.
Low-temperature ozonolysis of tetrafluoroethylene
(TFE) and hexafluoropropylene (HFP) by direct con-
tact of the reactants in the absence of solvents and
oxygen was studied in . At equimolar ratio of
ozone and perfluoroolefin, the corresponding ozon-
ides are formed at low temperatures (1403230 K) in
quantitative yield by addition of ozone across the
double bond. The resulting perfluoro ozonides are
stable up to 2503290 K and decompose at higher
temperatures, with TFE ozonide being more stable
than HFP ozonide. The decomposition products of
TFE and HFP ozonides in statu nascendi initiate poly-
merization of TFE [1, 2] and some other monomers
In this work, we studied the mechanism of cryo-
chemical ozonolysis of perfluoro-4-methyl-2-pentene
(HFP dimer, DHFP) and perfluoro-2,4-dimethyl-3-
ethyl-2-pentene (HFP trimer, THFP) and examined
the possibility of using the resulting ozonides as poly-
merization initiators. Our experimental procedure,
including sample preparation, excluded the uncontrol-
lable explosion mode of the reaction and allowed
ozonolysis of DHFP and THFP to be studied in the
absence of solvents and oxygen at direct contact of
ozone and perfluoroolefin.
DHFP and THFP were purified by double distilla-
tion (bp 323.2 and 383 K, respectively). Ozone was
generated by passing an oxygen stream through an
electric-discharge glass ozonizer equipped with exter-
nal and internal electrodes. The resulting ozone3oxy-
gen mixture was condensed in a trap cooled with
liquid nitrogen. Then, we removed oxygen from the
solution of ozone in liquid oxygen by vacuum distilla-
tion at 77 K, and the remaining crystalline ozone was
additionally purified by sublimation.
The phase state of the systems and the kinetics of
low-temperature ozonolysis and polymerization were
studied calorimetrically . Known amounts of a
fluoroolefin and ozone were condensed in a vacuum
at 77 K in special glass calorimetric cells and sealed.
The reaction was performed in a slowly warming-up
calorimeter, and the reaction course was monitored by
the heat release.
The IR spectra of the fluoroolefins and reaction
products were taken on a Specord IR-75 spectrometer
using standard cells.
On cooling to 77 K, DHFP passes into a glassy
state. In the course of heating of such a sample, we ob-
serve in the calorimetric curve a characteristic change
in the heat capacity due to a transition from the glassy
state to a supercooled liquid (T
110 K), crystalliza-
tion of the supercooled liquid (exothermic peak at
1203140 K), and melting at 160 K (Fig. 1, curve 1).
The heat of melting of DHFP, determined calorimetri-
cally, is 11.8+0.5 kJ mol
On heating a sample containing equimolar amounts
and DHFP, an exothermic reaction is observed
starting from approximately 210 K (Fig. 1, curve 2).
The rate of cryoozonation (heat release) increases
with temperature, reaching a maximum at 2403250 K.
The total activation energy of the reaction in the range
2103240 K is 90+5 kJ mol
. Upon further warming,