Copolymerization of vinylidene difluoride with hexafluoropropene in supercritical carbon dioxide

Vinylidene difluoride and hexafluoropropene are copolymerized in supercritical carbon dioxide at 280 bar and 50 degrees C by means of free radical copolymerization, initiated by diethyl peroxydicarbonate. The first stages of the reaction were monitored by turbidity measurements and the time/conversion curve was followed gravimetrically to measure the initial rates of polymerization. The obtained copolymers possessed bimodal molecular weight distributions, their average comonomer composition was well described by the Lewis-Mayo equation with the copolymerization parameters r(VDF) = 4.8 and r(HFP) = 0. The glass transition and melting temperatures of the copolymers are similar to that of the materials resulting from aqueous emulsion polymerization. (c) 2005 Wiley Periodicals, Inc.