Polymerization of Vinylidene Fluoride with Perfluoropolyether Surfactants in Supercritical Carbon Dioxide as a Dispersing Medium

The heterogeneous polymerization of vinylidene fluoride (VDF) was investigatedat 50 °C with supercritical carbon dioxide (scCO2) as a dispersing medium anddiethylperoxidicarbonate as an initiator in the presence of different perfluoropolyethersurfactants. When FLK 7004A ammonium carboxylate salts were used at a 5% (w/w)concentration with respect to VDF, with an initial pressure of 31–45 MPa and with anolefin concentration of about 5.5 mol/L, monomer conversions up to 63% were obtained,corresponding to a final solid content higher than 200 g/L, and the polymer was collectedat the end of the process in the form of a white powder completely composed ofmicrospheres. The effects of the density of the polymerization mixture, the monomerloading, and the surfactant concentration were studied. Collected experimental resultssuggest that Fluorolink ammonium perfluoropolyether carboxylic salts are the most effective surfactants yet tested in the dispersion polymerization of VDF in scCO2.