Controlled radical polymerization protocols for vinylidene fluoride (VDF) are still very elusive. MADIX polymerization of VDF has very rarely been reported. The synthesis of PVDF using MADIX solution polymerization was thus investigated in detail. More efficient protocols for solution polymerization were developed and afforded relatively well-defined PVDF. Careful polymer chain-end monitoring using MALDI-TOF as well as 1H, 19F, and HETCOR 1H–19F NMR revealed that VDF reverse additions and transfer to solvent reactions severely affect the control of the polymerization. Indeed, these unwanted reactions are responsible for a non-negligible loss of CTA and for the accumulation of nonreactive polymer chains in the reaction medium. MADIX polymerization lead to the synthesis of PVDF with high chain-end functionality. However, these PVDF chains cannot reinitiate the polymerization of VDF. This work is the first comprehensive study of the MADIX solution polymerization of VDF.

A new family of proton-conducting fluorocopolymers grafted by azole functions (imidazole, benzimidazole, 1H-1,2,4-triazole) was synthesized through grafting poly(2-iodoethyl vinyl ether-alt-chlorotrifluoroethylene) copolymers by commercially available 4(5)-hydroxymethylimidazole, 2mercaptobenzimidazole or 1H-1,2,4-triazole-3-thiol. Imidazole, benzimidazole, and 1,2,4-triazole-functionalized copolymers were characterized by 1 H and 19 F NMR spectroscopy and by thermal analyses (DSC and TGA), and were used in the preparation of blend membranes with sulfonated PEEK (s-PEEK). Properties of the three series of membranes were comprehensively investigated to understand the influence of the nature of the azole group (imidazole, benzimidazole, triazole) on membrane microstructure, thermal properties and water uptake. Proton conductivities of blend membranes comprising a fluorinated polymer component functionalized with triazole is significantly higher than those with imidazole or benzimidazole moieties, and detailed characterizations have identified an optimal composition in terms of the basic (−NH):acidic (−SO 3 H) groups ratio of 1.7 in this system, where the proton conductivity at 140 °C and at low relative humidity (<25%) is 7 mS.cm −1 for a blend membrane containing 60 wt % of s-PEEK and 40 wt % of poly(IEVE-alt-CTFE)-g-1H-1,2,4triazole-3-thiol 95% copolymer.