Collective polarization effects inβ-polyvinylidene fluoride and its copolymers with tri- and tetrafluoroethylene

The polar properties of the β phase of polyvinylidene fluoride (PVDF) and its copolymers with tri- and tetrafluoroethylene are investigated theoretically at different VDF-to-copolymer ratios. The calculations show that polarization in such polymers is described by cooperative, quantum-mechanical interactions between polymer chains, which cannot be viewed as a superposition of rigid dipoles. For β-PVDF, the monomer dipole moment is increased by 50% (from 20.3em0exto0.3em0ex30.3em0exD) as the isolated chains are brought together to form a crystal. In PVDF crystals containing copolymers, we observe a weakly parabolic dependence of monomer dipole moments on copolymer concentration.