Radical copolymerization of vinylidene fluoride with 8-bromo-1H,1H,2H-perfluorooct-1-ene: Microstructure, crosslinking and thermal properties

摘要

An original synthesis of 8-bromo-1H,IH,2H-perfluorooct-1-ene (BDFO) and its radical copolymerization with vinylidene fluoride (VDF), initiated by 2,5-bis(tert-butylperoxy)-2, 5-dimethylhexane at 134 degrees C, are presented. The fluorinated bromoalkene was obtained by dehydrobromination of 1,8-dibromo-1H,1H,2H,2H-perfluorooctane in a satisfactory yield. Although BDFO did not homopolymerize under radical initiation, it did copolymerize with VDF. The compositions of the resulting random type copolymers were calculated by means of F-19 NMR spectroscopy and allowed the quantification of the respective amounts of both comonomers in the copolymers, showing good incorporation of the brominated monomer. Nevertheless, obtaining PVDF copolymers containing a high molar percentage of BDFO in good yields was difficult to achieve from initial molar ratios of BDFO higher than 9.2 mol-. Radical terpolymerization of VDF, BDFO and hexafluoropropene (HFP) was also successfully achieved. BDFO contents in these co- or terpolymers ranged from 3.6 to 12.2 mol-. The bromoalkene acted as a cure site monomer and the resulting poly(VDF-co-BDFO) copolymers were crosslinked via the bromine atom in the presence of a triallyl isocyanurate/peroxide system. The materials obtained led to more thermally stable copolymers than the uncured ones and their thermostabilities were compared to those of commercially available poly(VDFco-HFP) copolymers crosslinked using diamines. GRAPHICS