γ-radiation induced structural changes in PVDF and VDF-TFE copolymer

The structure of poly(vinylidenefluoride) (PVDF) and its copolymer with tetrafluoroethylene (TFE) exposed to various doses of γ-radiation in air was studied by X-ray diffraction analysis. The irradiation of isotropic PVDF samples containing crystalline α-modification is accompanied by redistribution of the diffraction intensity between some inter- and intramolecular reflections. This is related to a partial transformation of the α phase into its polar modification under the action of local fields of a space charge produced by γ-quanta in the polymer matrix. In the isotropic copolymer samples with coexisting nonequilibrium para- and ferroelectric phases, the irradiation leads to a radiation-induced transition of the paraelectric to ferroelectric type. In the uniaxially drawn copolymer samples containing both isotropic and anisotropic (mesomorphic) components of the paraelectric phase, the irradiation may result in increasing longitudinal dimensions of the ferroelectric crystallites.