Abstract
In the search for new fluorinated electroactive copolymers, 0–8 mol% of 2,3,3,3-tetrafluoropropene(1234yf) was terpolymerized with vinylidene fluoride (VDF) and trifluoroethylene (TrFE). The reactivity inbatch solution polymerization of 1234yf was evaluated. First, reactivity ratio measurements showed thathomopropagation of 1234yf is favored compared to cross propagation with VDF or TrFE (rVDF-1234yf =0.079, r1234yf-VDF = 2.6; and rTrFE-1234yf = 0.089, r1234yf-TrFE = 4.9, at 48 °C). Then, the study of a typicalbatch solution polymerization revealed that the polymerization time was not affected by the initialamount of 1234yf and that polymer chains with strong compositional heterogeneity were obtained. Based onthese results, a semi-continuous aqueous suspension polymerization process was used for the synthesis ofterpolymers with a more homogeneous composition. Calculation of addition probabilities exemplified thechanges in the drift of composition. The monomer sequences in the poly(VDF-ter-TrFE-ter-1234yf) terpolymers,carefully studied by 19F NMR spectroscopy, were not affected by the polymerization process and weredominated by VDF-TrFE and VDF-1234yf dyads. Finally, the thermal and ferroelectric (FE) properties of thehomogeneous and heterogeneous terpolymers were characterized and compared. In the case of heterogeneousterpolymers, increasing the 1234yf content from 0 to 6 mol% slightly decreased the crystal size andthe overall crystallinity (Tm = 60 °C and ΔHm = 144 J g−1 for a poly(VDF66-ter-TrFE26-ter-1234yf8) terpolymer).On the contrary, for homogeneous terpolymers, 5 mol% of 1234yf strongly affected both the Curie andmelting transitions at TCurie = 37 °C and Tm = 107 °C. The reduced coercive field (Ec = 40 MV m−1) andremnant polarization (Pr = 22 mC m−2) for the homogeneous terpolymer compared to a referencepoly(VDF65-co-TrFE35) (Ec = 62 MVm−1 and Pr = 45 mCm−2) transcribed modifications of the FE domains.