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Preparation and crystallization behavior of poly(vinylidene fluoride-ter-chlorotrifluoroethylene- ter-trifluoroethylene)



Several poly(vinylidene fluoride-ter-chlorotrifluoroethylene-ter-trifluoroethylene) terpolymers, including 68 mol % vinylidene fluoride, were prepared by the partial reduction of chlorine in poly(vinylidene fluoride-co-chlorotrifluoroethylene) copolymers. The terpolymers were then allowed to crystallize under two sets of conditions: (1) crystallized from solution (in N,N-dimethylformamide) at 35°C for 108 h and (2) annealed at temperatures 5°C below their respective melting points for 11 h. The effect of the chlorotrifluoroethylene (CTFE) content and crystallization conditions on the crystallization behavior of the terpolymers was investigated by X-ray diffraction, Fourier transform infrared spectroscopy, and differential scanning calorimetry. The results show that with increasing CTFE content, the terpolymers contained less of the β phase (it even disappeared), which had an all-trans chain conformation, and more of the γ phase was found, which became prominent with the trans–trans–trans–gauche conformation. The crystallinity, crystal size, fusion enthalpy, and melting temperatures of the terpolymers decreased with increasing CTFE content. Compared with annealed terpolymers, the terpolymers crystallized from the solution at 35°C included more polar components that contained more trans conformations but had lower crystallinities, melting temperatures, and fusion enthalpies and smaller crystal sizes. These results suggest that crystallization from the solution may be helpful in forming polar crystals, whereas an annealing process at a high temperature is beneficial in perfecting the crystal structure. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011