Investigation of structural changes in PVDF by modified X-ray texture methods

Polyvinylidenefluoride films of α and α_p phases have been investigated by wide-angle X-ray scattering texture analysis before and after poling in a strong electric field (E=180 MV/m). Changes in crystalline structure and orientation are discussed on the basis of these results. After uniaxial drawing and before poling the crystalline c axes are oriented along the draw direction and the dipole axes (crystalline a axes) show a slightly preferred orientation toward the transverse T direction of the sample. A partial conversion of α-phase crystallites in polar α_p-phase crystallites and a preferred orientation of the polar a axes along the poling field direction N is observed after poling. Crystallites having a broad orientation spectrum between N and T are involved in the conversion. A qualitative discussion of the structural changes in the PVDF films due to poling is given