Fluorinated block copolymers containing poly(vinylidene fluoride) or poly(vinylidene fluoride-co-hexafluoropropylene) blocks from perfluoropolyethers: Synthesis and thermal properties

Abstract

PFPE-b-PVDF and PFPE-b-poly(VDF-co-HFP) block copolymers [where PFPE, PVDF, VDF, and HFP represent perfluoropolyether, poly(vinylidene fluoride), vinylidene fluoride (or 1,1-difluoroethylene), and hexafluoropropylene] were synthesized by radical (co)telomerizations of VDF (or VDF and HFP) with an iodine-terminated perfluoropolyether (PFPE-I). Di-tert-butyl peroxide (DTBP) was used and was shown to act as an efficient thermal initiator. The numbers of VDF and VDF/HFP base units in the block copolymers were assessed with 19F NMR spectroscopy. According to the initial [PFPE-I]o/[fluoroalkenes]o and [DTBP]o/[fluoroalkenes]o molar ratios, fluorinated block copolymers of various molecular weights (1500-30,300) were obtained. The states and thermal properties of these fluorocopolymers were investigated. The compounds containing PVDF blocks with more than 30 VDF units were crystalline, whereas all those containing poly(VDF-co-HFP) blocks exhibited amorphous states, whatever the numbers were of the fluorinated base units. All the samples showed negative glass-transition temperatures higher than that of the starting PFPE. Interestingly, these PFPE-b-PVDF and PFPE-b-poly(VDF-co-HFP) block copolymers exhibited good thermostability.