Strain-enhanced nanoparticle electrostrictive polymer blends for actuator applications

The electrostrictive terpolymer poly(vinylidene fluoride-trifluoroethylene-1,1-chlorofluoroethylene) - P(VDF-TrFECFE) - exhibits higher field-induced strain and larger dielectric constant (> 30) than most materials. In this paper we show that the strain of this terpolymer can be increased even more by mixing it with BaTiO3 nanoparticles of high dielectric constant. For our investigation, actuator-like stacks on basis of terpolymer / nanoparticles blend thin films were prepared. Measurements of electric-field induced strain in the blend thin films, carried out with a Michelson interferometric set-up, show that indeed that the electrostrictive strain increases with increasing the nanoparticle content in the blend. Structural characterization by means of X-ray diffraction and phase transitions analysis with differential scanning calorimetry (DSC) indicate that the crystalline phase in the terpolymer host has been altered by the presence of nanoparticles. Additional measurements reveal that the dielectric permittivity of the obtained blend thin films is larger than that of the terpolymer. For the blend containing 1 wt% nanoparticles a dielectric permittivity of about 40 and an electrostriction coefficient of about 4 times larger than that of terpolymer were determined. Besides we show that by employing optimum annealing temperatures, the film quality with respect to its surface roughness can be improved.