Abstract
The aqueous radical homopolymerization of vinylidene fluoride (VDF), as well as its co-polymerizations with hexafluoropropylene (HFP) or perfluoromethyl vinyl ether (PMVE), and its ter-polymerization with HFP and PMVE, initiated by trifluoromethyl radicals (•CF 3), generated from ammonium persulfate (APS) and potassium trifluoromethyl sulfinate (CF 3 SO 2 K) redox system are presented. The optimization of the experimental conditions in terms of initial reactant molar ratios, temperature and reaction time was achieved. The best results were obtained at 60 o C, in water, without any surfactant, using 0.9 eq of APS as the oxidant with respect to CF 3 SO 2 K. PVDF, poly(VDF-co-HFP), poly(VDF-co-PMVE), or poly(VDFter-PMVE-ter-HFP) co-polymers were obtained in high yields (varying between 89 and 100%), and with molar masses up to 113,000 g/mol. The 1 H and 19 F NMR spectroscopy revealed that, under optimized conditions, the formed chain-ends were exclusively CF 3 or CF 2 H. The influence of the nature of the chain-end on the thermal stability showed that PVDFs terminated by CF 3 were more stable than their analogues bearing sulfate end-groups by 120 o C. In addition, the prepared CF 3-PVDFs had 53% of crystallinity (compared to 47% for PVDF initiated from APS alone), which offers excellent resistance to conventional organic solvents including dimethyl sulfoxide, acetone and dimethyl formamide.