Molecular theory of piezoelectricity of α‐helical polypeptide

A molecular theory of the piezoelectric constant of the α‐helical backbone of polypeptide is developed on the basis of fluctuation formalism. The piezoelectric constant, electric susceptibility, and elastic compliance of the α‐helix are calculated through the method of molecular lattice dynamics by use of normal‐coordinate analysis. Displacements of each atom due to the external stress exerted upon the backbone are also calculated. The piezoelectricity of the α‐helix is concluded to arise mainly from rotation of the CONH bond. The value of the piezoelectric constant of poly(γ‐benzyl‐L‐glutamate) film calculated from the above theoretical constants along with a composite theory is found to agree reasonably with experiment.