Structural variations in ethylene‐tetrafluoroethylene copolymers as a function of composition and temperature

Abstract

AbstractEthylene‐tetrafluoroethylene copolymers, containing 50–80 mol‐% of tetrafluoroethylene (TFE) units, were investigated by wide‐angle X‐ray scattering (WAXS) and dynamic mechanical analysis (DMA). With increasing TFE content, a shift toward low temperatures of the crystalmesophase transition is observed; only the mesophase is observed for high TFE content (e.g., the 80 mol‐% TFE copolymer). On the basis of a conformational analysis, a gradual change, with the TFE content, of the chain conformation from a planar zig‐zag conformation to a conformation built up locally of very short helical stretches is indicated. For both the crystal and the mesophase structure the size of the domains in which the ordered disposition of the chain axes is maintained is larger for copolymers with higher TFE content, where a lower degree of local order is expected.