Molecular dynamics of ferroelectric polymeric systems as studied by incoherent quasielastic neutron scattering

We have studied by incoherent quasielastic neutron scattering the molecular dynamics of the ferroelectric copolymers of vinylidene fluoride and trifluoroethylene with two different molar ratios. Thermal hysteresis effects accompanying the structural changes observed in these materials are found. In the temperature range investigated three motions were identified: (i) a vibrational motion of Debye-Waller type which shows increasing amplitude until the vicinity of the Curie temperature and then it follows a ${\mathit{Q}}^4$ law, (ii) a slow jump diffusive motion of each chain in the restricted volume defined by other chains, thermally activated with an activation barrier of ≊8 kcal/mol, and (iii) a fast local diffusive motion with only some fraction of the chains concerned.