Résumé
The radical homopolymerization of vinylidene fluoride (VDF) and its copolymerization with several comonomers such as H2C=CRA(CF3) (where RA stands for H, F, CO2R (R=H or tBu) or F2C=CFRB (RB : H, CF3, OCF3) initiated by CF3 radical generated by a perfluorinated branched persistant radical (PPFR) are presented. In all cases, the regioselective radical addition of CF3 onto the methylene site of VDF was noted and well evidenced in 19F NMR spectra in the presence of a quintet centered at -61 ppm. The microstructures of the resulting PVDF, poly(VDF-co-H2C=CRA(CF3) or poly(VDF-co-F2C=CFRB) (co)polymers displayed a CF3 end-group and 19F NMR spectroscopy enabled to assess both the molecular weights of such above (co)polymers and the molar percentages of VDF and H2C=CRA(CF3) and F2C=CFRB comonomers. This novel initiating system some times produced remarkable high molecular weights of fluoropolymers which worth 200,000 g-mol-1. Molecular weights depended on the [PPFR]o/([VDF]o + [comonomers]o) initial molar ratio and the lower that ratio the higher the molecular weights. Thermal properties of these resulting (co)polymers were also investigated and compared to those of the literature. Although the kinetics of the radical copolymerization were not studied, the presence of branched persistent radical did not disturb the reactivities of the comonomers as well as that persistent derived adduct was unable to initiate the polymerization and never involved in the termination step of the polymerization as evidenced from the 19F NMR spectra of the resulting copolymers. A feed ratio of ca. 20 mol% of MAF (or MAF-TBE) led to a tendency to alternating poly(VDF-alt-MAF or MAF-TBE) copolymers. High reactivities of 1234, HFP, PMVE comonomers were noted in contrast to those of MAF, MAF-TBE, TrFE and TFP. Further work on the copolymerization of CTFE is also presented.