First RAFT/MADIX radical copolymerization of tert-butyl 2-trifluoromethacrylate with vinylidene fluoride controlled by xanthate
Résumé
The radical copolymerization of tert-butyl 2-trifluoromethacrylate (MAF-TBE) with vinylidene fluoride (VDF), initiated by bis(4-tert-butyl cyclohexyl) peroxydicarbonate and controlled by O-ethyl-S-(1- methyloxycarbonyl) ethyl xanthate as a chain transfer agent (CTA) is presented. Molar masses ranged between 1500 and 4000 g mol 1 while polydispersity indices (PDIs) were lower than 1.8. Various experimental conditions such as different radical initiators, solvents, initial [initiator]o/([VDF]o + [MAFTBE] o) and [CTA]o/([VDF]o + [MAF-TBE]o) molar ratios, and their effect on the copolymerization (in terms of molar percentages of both comonomers in the copolymer, yields, molar masses, and thermal properties) were examined and discussed. These poly(VDF-co-MAF-TBE) copolymers bearing a xanthate end-group were further involved in controlled radical polymerizations of vinyl acetate (VAc) or VDF leading to poly(VDF-co-MAF-TBE)-b-poly(VAc) and poly(VDF-co-MAF-TBE)-b-poly(VDF) block copolymers, respectively. The success of these radical copolymerizations of MAF-TBE contrasts with its homopolymerization that occurred with difficulty and produced low molecular weight-homopolymers in low yields. On the other hand, the controlled character of the polymerization involving O-ethyl-S-(1-methyloxycarbonyl) ethyl xanthate was confirmed by the evolutions of log([M]o/[M]) and MAF-TBE conversion versus time and by size exclusion chromatography that were found to be linear. All the structures of the obtained intermediates and block copolymers were characterized by 1H and 19F NMR spectroscopy and size exclusion chromatography to assess the molar percentages of VDF and MAF-TBE and the molecular weights and PDIs, respectively. The thermal and surface properties of such original copolymers were determined by thermogravimetric analysis and water contact angle measurements, respectively.