Synthesis and polymerization of fluorinated monomers bearing a reactive lateral group. Part 10. Copolymerization of vinylidene fluoride (VDF) with 5-thioacetoxy-1,1,2-trifluoropentene for the obtaining of a novel PVDF containing mercaptan side-groups

The synthesis of novel perfluorovinyl thioacetoxy monomer (FSAc) and its copolymerization with vinylidene fluoride (VDF; also called 1,1- difluoroethylene) are presented. This monomer was obtained in good yield from the photochemical addition of thiol acetic acid to 1,1,2-trifiuoro-1,4- pentadiene. It was first hydrolyzed into 4,5,5-trifluoro-4-ene mercaptopentane, which did not homopolymerize, but under radical conditions underwent mainly a five-member cyclization. FSAc monomer was copolymerized with VDF either in bulk or in solution. 19F-NMR spectroscopy enabled one to quantify the respective amount of each monomeric unit in the copolymer. The reactivity ratios, ri, of both comonomers were determined from the Kelen and Tüdös and the Tidwell and Mortimer methods and were found to be r VDF = 0.63 and 0.60 and rFSAc = 0.43 and 0.41 at 120°C, respectively. An azeotropic point was observed at 61 mol% of VDF and under this VDF percentage, lower incorporation of FSAc in the copolymer took place. Alfrey-Price's Q and e values of this trifluorovinyl thioacetoxy monomer were calculated to be 0.022 (from QVDF = 0.008) or 0.044 (from Q VDF = 0.015) and + 1.56 (vs. eVDF = 0.40) or + 1.66 (vs. eVDF = 0.50), respectively, indicating that FSAc is an electron-accepting monomer. These comonomers led to random fluorinated copolymers bearing thioacetoxy side-groups, being easily hydrolyzed into lateral thiol functions. This original PVDF containing mercaptan side-groups was cured by 1,5-hexadiene to produce an insoluble vulcanized network. © 1999 VSP.