Viscoelastic Behavior of Poly (γ-methyil--glutamate)

Abstract

The dynamic mechanical properties of poly (γ-methyl L-glutamate) (PMLG) fibers and films were observed. The undrawn fiber and films, which were found to have an α-helical conformation, showed a maximum in the dynamic loss E" curve at 150-160°C. This dispersion was assumed to be due to the slipping motion of the unoriented helices in the amorphous region. The fiber sample slowly drawn at 150°C and also the oriented film exhibited another maximum in the E″ curve at above 180°C. This maximum was assigned to a slipping motion in the crystalline region. The cold-drawn fiber was found to be mainly in the β-form and showed a maximum in the E″ curve at about 100°C. This dispersion was assigned to a segmental motion in the random-coil region. The conformation of PMLG in films cast from the random-coil solvents, dichloroacetic acid and trifluoroacetic acid (TFA), was found to be α-helical. It was assumed that the transformation from random-coil to α-helical occurred in the casting process. The film cast from TFA-formic acid was mainly in the β-form. But a contribution of the random-coil region to the dynamic mechanical dispersion was not found.