Microstructure and electromechanical responses in semicrystalline ferroelectric relaxor polymer blends

Ferroelectric relaxor poly(vinylidene fluoride-trifluoroethylene-1,1-chlorofluoroethylene) [P(VDF-TrFE-CFE)] terpolymer with VDF/TrFE/CFE composition of 59.2∕34.6∕7.2 (mole %) exhibits a high dielectric constant (∼50) around room temperature and strong electromechanical response. It can form miscible blends with poly(methyl methacrylate) (PMMA). This paper reports the results of a systematic investigation of the influence of PMMA on the microstructure and electromechanical responses of the terpolymer blends with PMMA content up to 10wt%. It was found that the crystallinity of the blends decreases nearly linearly with increased PMMA content. Since the dielectric constant and polarization response of P(VDF-TrFE-CFE) terpolymer are mainly from the crystalline region, these properties accordingly exhibit proportional reduction with increased PMMA concentration. Nevertheless, a small amount (∼5wt%, for instance) of PMMA can raise the elastic modulus of the blend quite markedly while the field-induced strain level is not affected very much. Consequently, the elastic energy density can be enhanced in the blends. As a result, the electromechanical efficiency of blends in the composition range investigated is also significantly improved. In addition, the mechanical loss factor is dramatically decreased at room temperature by blending with PMMA.