Radical solution copolymerisation of vinylidene fluoride with hexafluoropropene

The radical copolymerisation in solution of vinylidene fluoride (or 1,1-difluoroethylene (VDF)) with hexafluoropropylene (HFP) initiated by di-tert-butyl peroxide is presented. A series of eight copolymerisation reactions was investigated with initial [VDF]o/[HFP]o molar ratios ranging from 5.0/95.0 to 85.2/14.8. Both co-monomers copolymerised in this range of copolymerisation. Moreover, only VDF homopolymerised in these conditions. The copolymer compositions of these random-type copolymers were calculated by means of 19F NMR spectroscopy which allowed the respective amount of each monomeric unit in the copolymer to be quantified. The Tidwell and Mortimer method led to the assessment of the reactivity ratios, ri, of both co-monomers showing a higher incorporation of VDF in the copolymer (rHFP = 0.12 ± 0.05 and rVDF = 2.9 ± 0.6 at 393 K). Alfrey–Priceʹs Q and e values of HFP were calculated to be 0.002 (from QVDF = 0.008) or 0.009 (from QVDF = 0.015) and +1.44 (versus eVDF = 0.40) or +1.54 (versus eVDF = 0.50), respectively, indicating that HFP is an electron-accepting monomer. The thermal properties of these fluorinated copolymers were also determined. Except for those containing a high amount of VDF, they were amorphous. Each showed one glass transition temperature (Tg) only, and from known laws of Tg, that of the homopolymer of HFP was assessed. It was compared with that obtained from the literature after extrapolation and is discussed.