Molecular mechanism for elongation: poly(vinylidene fluoride) form II

Elongation of an unoriented sample of poly(vinylidene fluoride) form II at high temperature (above 140 °C) results in a uniaxially oriented sample of form II during so-called necking. The short-range and long-range order parameters of poly(vinylidene fluoride) form II and measures of the structural order on thec-projection are characterized by the intensity and half-width of the 120 reflection. The elongation under the same condition gives almost the same order parameters, independent of the order parameters before the elongation. Furthermore, the dependence of the order parameters on the elongation temperature behaves in the same way as the dependence of the quenched unoriented sample on the annealing temperature. This suggests that the elongation of the sample during necking corresponds to the crystallization or recrystallization after a much disordered state, approximately molten state; this supports the mechanism proposed by Yoon and Flory.