Nanometric and Macroscopic Electroactive Response of P(VDF-co-TrFE) Copolymers and P(VDF-ter-TrFE-ter-CTFE) Terpolymers

Abstract

The knowledge and the improvement of the electric responsiveness of P(VDF-co-TrFE) copolymer and P(VDF-ter-TrFE-ter-CTFE) terpolymer films are essential for their application in electronic devices. Many factors affect the performances of these electroactive films, such as the chemical composition and the thermal treatment. In this article, the response to an external electric field of copolymer and terpolymer films at both the nanometric and macroscopic scales is studied. The response at the nanometric scale is analyzed by piezoresponse force microscopy on thin films (∼100 nm thick), while that at the macroscopic scale is analyzed by measuring the electric displacement–electric field loops on thick films (∼20 μm thick). The effect of the chemical composition (CTFE content) is found to be crucial, both at the nanometric and macroscopic scales, in defining the electroactive behavior of the samples, while the thermal treatment seems more exacerbated at the nanometric scale. The orientation, shape, and size of the crystalline lamellae affect the orientation of the electric dipoles, which are thus more or less sensitive to the applied electric field. The controlled growth of edge-on lamellar stacks, obtained after crystallization from the melt at low cooling rates, provides a better piezoresponse of the film.