Piezoelectricity in oriented films of poly(γ‐benzyl‐L‐glutamate)

Abstract

Abstract Oriented films of poly(γ‐benzyl L ‐glutamate) (PBLG) were prepared by two methods. Films of PBLG cast from chloroform solutions were elongated by rolling at 70°C. A solution of PBLG in methylene bromide was placed in a magnetic field of about 7000 gauss and the solvent was slowly evaporated for a few days until an oriented film was obtained. The real and imaginary components of the complex piezoelectric strainconstant d 25 * = d 25 ′ − jd 25 ″ were determined over the temperature range from −180°C to +180°C at a frequency of 20 Hz. The constants showed dispersions at about 20°C and about 100°C, where dynamic viscoelastic dispersions were also observed. Degree of crystallinity X c and degree of orientation II a of crystallites were determined from x‐ray diffraction diagrams. The product X c II α and the value of d 25 ′ at room temperature were found to be linearly related, and both showed a maximum at an elongation ratio of 1.5 (the ratio of the final to initial length) for roll‐oriented films and at an initial solution concentration of 15% by weight for magnetically oriented films. The largest values of d 25 ′ were approximately 2 × 10 −12 and 4 × 10 −12 coulomb/newton, respectively, at room temperature.