Primary piezoelectric relaxation in copolymers of β-hydroxybutyrate and β-hydroxyvalerate

Abstract

Oriented films of a copolymer of 75 mol% ß-hydroxybutyrate and 25 mol% ß-hydroxyvalerate produced from microorganism showed intrinsic shear piezoelectricity. Complex piezoelectric constant e=e'-ie", elastic constant c= c'+ ic" and dielectric constant ε= ε' — iε" were dynamically determined at 0.8–100 Hz and at −40 −40°C. Relaxational behaviors of these quantities were observed around glass transition temperature. Assuming time-temperature equivalence, master curves for these three constants were well composed. The temperature variation of shift factor fitted well to WLF equation. The theory of spherical dispersion model, in which piezoelectric crystalline are dispersed in relaxing amorphous medium, was satisfactorily applied for the piezoelectric relaxation.