Synthesis of ω‑Iodo and Telechelic Diiodo Vinylidene Fluoride-Based (Co)polymers by Iodine Transfer Polymerization Initiated by anInnovative Persistent Radical

International audienceThe synthesis of ω-iodo and telechelic diiodovinylidene fluoride (VDF)-based (co)polymers by iodinetransfer polymerization (ITP) of VDF initiated by a trifluoromethylradical (generated by perfluoro-3-ethyl-2,4-dimethyl-3-pentyl persistent radical, PPFR) is presented. Reactions werecarried out in the presence of different chain transfer agents(CTAs, such as trifluoroiodomethane, 1,4-diiodoperfluorobutane,and molecular iodine) with/without tert-butyl 2-trifluoromethacrylate(MAF-TBE). Experimental conditions (natureof the solvents and CTAs, time, temperature, and initial[VDF]0:[CTA]0:[initiator]0 molar ratios) were varied toinfluence the yield of the reaction (up to 86%), the molar masses (Mn), dispersity values (Đ), chain end functionalities, andmicrostructures of the obtained polymers. Detailed kinetics study enabled to confirm the well-controlled polymerization: (i)synthesis of iodinated polymers with different molar masses (Mn,SEC = 1110−5800 g mol−1) and low Đ values (≤1.30), justsimply by varying the [VDF]0:[CTA]0 initial molar ratio; (ii) linear increase of Mn versus conversion, maintaining low Đ values(≤1.28); (ii) the presence of favored -CH2CF2-I end functionality up to 80% monomer conversion. The compositions andmicrostructures of all the obtained copolymers were characterized by 1H and 19F NMR spectroscopies. Deeper mechanisticinvestigation of the ITP of VDF initiated by •CF3 radical from PPFR was carried out. In the presence of CF3I as the CTA, thecompetitive presence of CF3 end group in CF3-PVDF-I was evidenced to arise from the CTA and showed a negligible amount ofCF3-PVDF oligomer dead chains initiated from •CF3 radical from PPFR. Very low chain defects (due to reversed -CH2CF2-CF2CH2- and -CF2CH2-CH2CF2- in VDF-VDF dyads, even the absence of such a later one) led to high melting points(161−173 °C) of the resulting polymers, as revealed by differential scanning calorimetry. The thermal stability of the polymersincreased with higher Mn values reaching 270 °C under air, while for copolymers containing MAF-TBE, the degradation occurredfrom 170 °C attributed to the release of isobutene from the tert-butyl side groups