Abstract
The synthesis of alpha,β-difluoroacrylic acid (FHCdCF-CO2H, DiFAA) and its radical copolymerization with vinylidene fluoride (CH2dCF2, VDF) are presented. First, DiFAA was synthesized in three steps from the radical addition of methanol onto 1,2-dichloro-1,2-difluoroethylene leading to HCFClCFClCH2OH in 78% yield. Then, oxidation of the hydroxymethyl end-group followed by zincmediated dehalogenation of 2,3-dichloro-2,3-difluoropropanoic acid led to (Z) isomer of DiFAA in 29% overall yield. The homopolymerization of DiFAA was successfully achieved by radical polymerization initiated by tert-butylperoxypivalate (TBPPi) at 74 C in 32% yield. Its radical copolymerization with VDF was carried out for the first time and at various compositions leading to functional poly(VDF). The resulting poly(VDF-co-DiFAA) copolymers, characterized by 1H and 19F NMR spectroscopies, exhibited a statistic microstructure. The kinetics of this radical copolymerization led to the assessment of the reactivity ratios (rDiFAA = 0.86 and rVDF = 0.34 at 74 C), and showed that DiFAA was more reactive than VDF in copolymerization. Thermal properties of these poly(DiFAA-co-VDF) copolymers were also investigated. Differential scanning calorimetry analyses showed a decrease of the glass transition temperature (Tg) with increasing VDF content. Calculations using the Fox's equation led to the determination of the Tg for poly(DiFAA) homopolymer (Tg = 145 C) in good agreement with the literature. Thermogravimetric analyses displayed increased thermostability of the resulting copolymers with increasing VDF content