Abstract
The radical copolymerization of vinylidene fluoride (VDF) and 1-bromo-2,2-difluoroethylene (BDFE) in 1,1,1,3,3-pentafluorobutane solution at different monomer molar ratios (ranging from 96/4 to 25/75 mol %) and initiated by tert-butylperoxypivalate (TBPPI, mainly) is presented. Poly(VDF-co-BDFE) copolymers of various aspects (from white powders to yellow viscous liquids) were produced depending on the copolymer compositions. The microstructures of the obtained copolymers were characterized by 19F and 1H NMR spectroscopy and by elementary analysis and these techniques enabled one to assess the contents of both comonomers in the produced copolymers. VDF was shown to be more incorporated in the copolymer than BDFE. From the extended Kelen and Tudos method, the kinetics of the radical copolymerization led to the determination of the reactivity ratios, ri, of both comonomers (rVDF ¼ 1.20 6 0.50 and rBDFE ¼ 0.40 6 0.15 at 75 °C) showing that VDF is more reactive than BDFE. Alfrey-Price's Q and e values of BDFE monomer were calculated to be 0.009 (from QVDF = 0.008) or 0.019 (from QVDF = 0.015) and þ1.22 (vs. eVDF = 0.40) or þ1.37 (vs. eVDF = 0.50), respectively, indicating that BDFE is an electron-accepting monomer. Statistic cooligomers were produced with molar masses ranging from 1,800 to 5,500 g/mol (assessed by GPC with polystyrene standards). A further evidence of the successful copolymerization was shown by the selective reduction of bromine atoms in poly(VDF-co-BDFE) cooligomers that led to analog PVDF. The thermal properties of the poly(VDF-co-BDFE) cooligomers were also determined and those containing a high VDF amount exhibited a high thermal stability.