FERROELECTRIC BEHAVIOR OF THIN-FILMS OF VINYLIDENE FLUORIDE TRIFLUOROETHYLENE/HEXAFLUOROPROPYLENE COPOLYMER/

Ferroelectricity in vinylidene fluoride (VDF), trifluoroethylene (TrFE ) and hexafluoropropylene (HFP) copolymers (P(VDF/TrFE/HFP)) with a lo w HFP content (lower than 11mol%) has been investigated primarily thro ugh switching measurements using P(VDF/TrFE) as a comparison. Switchin g phenomena as a result of ultimately 180 degrees rotations of individ ual molecular chains around their axes in crystalline regions were obs erved in P(VDF/TrFE/HFP) with an HFP content lower than 2.5 mol%. With increasing HFP content in P(VDF/TrFE/HFP), the amount of reversed pol arization decreases, and the dielectric permittivity at the Curie poin t becomes smaller. However, the switching times have very low dependen ce on the HFP content of P(VDF/TrFE/HFP). These results suggest that n oncrystalline regions in P(VDF/TrFE/HFP) are similar to those in P(VDF /TrFE), and the disorder in crystalline regions of P(VDF/TrFE/HFP) inc reases compared to that in crystalline regions of P(VDF/TrFE).