Copolymerization of Vinylidene Fluoride and Acrylic Acid in Supercritical Carbon Dioxide

The free-radical copolymerization of vinylidene fluoride (VDF) and acrylic acid (AA) was carried out in supercriticalcarbon dioxide using both precipitation and dispersion techniques in the presence of an ammonium carboxylate perfluoropolyethercompound. Formation of a copolymer was confirmed by variable contact time CP MAS NMR spectroscopy. Macromolecularmatrices were significantly enriched in AA with respect to the initial feed composition and we found that the nonfluorinatedmonomer has a much higher reactivity ratio with respect to VDF.The cumulative concentration, crystallinity, and water affinity of the synthesized copolymers could be modified changing the initial feed composition, the density of the polymerization mixture, the specific interfacial area of the polymer phase, and the polymerization time. The solubility of the macromolecular product inwater was greatly affected by its composition.