Piezoelectric Constant in Oriented β-form Polypeptides

Abstract

Piezoelectric constant and its temperature variation are determined in oriented films of poly-γ-methyl-L-glutamate with the β-form molecular conformation. Semi-quantitative calculation of piezoelectric constants is performed on the basis of a molecular model of pleated sheet structure. Shearing force in the plane of the sheet brings about slide between two adjacent extended polypeptides molecules. The plane of CONH dipole then rotates around the axis of the main chain, which produces an electric polarization. The estimated piezoelectric stress-constant for a single crystal of β-form poly-γ-methyl-L-glutamate is e ₁₄=-2.8×10⁴ cgse.s.u.. If the degree of crystallinity X _c =5%, the degree of orientation \varPi_α=70% and the symmetry due to uniaxial orientation of the molecules are taken into consideration, e ₁₄=-5×10² cgse.s.u. is obtained for the present specimen, which agrees with the experimental observation.