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

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• 作者：Sanjib BanerjeeYogesh Patil ; Taizo Ono ; Bruno Ameduri
• 刊名：Macromolecules
• 出版年：2017
• 出版时间：January 10, 2017
• 年：2017
• 卷：50
• 期：1
• 页码：203-214
• 全文大小：732K
• ISSN：1520-5835

文摘

The synthesis of ω-iodo and telechelic diiodo vinylidene fluoride (VDF)-based (co)polymers by iodine transfer polymerization (ITP) of VDF initiated by a trifluoromethyl radical (generated by perfluoro-3-ethyl-2,4-dimethyl-3-pentyl persistent radical, PPFR) is presented. Reactions were carried 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 (nature of the solvents and CTAs, time, temperature, and initial [VDF]₀:[CTA]₀:[initiator]₀ molar ratios) were varied to influence the yield of the reaction (up to 86%), the molar masses (M_n), dispersity values (Đ), chain end functionalities, and microstructures of the obtained polymers. Detailed kinetics study enabled to confirm the well-controlled polymerization: (i) synthesis of iodinated polymers with different molar masses (M_n,SEC = 1110–5800 g mol^–1) and low Đ values (≤1.30), just simply by varying the [VDF]₀:[CTA]₀ initial molar ratio; (ii) linear increase of M_n versus conversion, maintaining low Đ values (≤1.28); (ii) the presence of favored -CH₂CF₂-I end functionality up to 80% monomer conversion. The compositions and microstructures of all the obtained copolymers were characterized by ¹H and ¹⁹F NMR spectroscopies. Deeper mechanistic investigation of the ITP of VDF initiated by ^•CF₃ radical from PPFR was carried out. In the presence of CF₃I as the CTA, the competitive presence of CF₃ end group in CF₃-PVDF-I was evidenced to arise from the CTA and showed a negligible amount of CF₃-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 polymers increased with higher M_n values reaching 270 °C under air, while for copolymers containing MAF-TBE, the degradation occurred from 170 °C attributed to the release of isobutene from the tert-butyl side groups.