Actuation efficiency of polyvinylidene fluoride-based co- and ter-polymers

Abstract Poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) (P(VDF-TrFE-CTFE)) ter-polymers reach strain up to 4% with the application of an electric field. This is several times larger than PVDF-TrFE co-polymers. However this large strain comes with reduced stiffness, which is detrimental to ter-polymers integration in heterogeneous structures. Here we compare the actuation capabilities of cantilevers with P(VDF-TrFE-CTFE) and P(VDF-TrFE) as active layer. Our ter-polymers exhibit CTFE composition ranging from 0 to 9.7%. We compared the electrical and mechanical displacements as well as the electromechanical coupling of these devices. We found that ter-polymer devices with CTFE ratio below 8% are ferroelectric whereas they become relaxor beyond 8% of CTFE. The maximum deflections of all cantilevers at high electric field are comparable, though slightly larger for the ter-polymer with 5% CTFE. The main finding of this paper concerns the effective electromechanical coupling of ter-polymers that is at best only half of the co-polymer one.