Dynamic Mechanical Properties of Poly(α-amino acid)s. II. Poly(ε-N-benzyloxycarbonyl-L-lysine)

Abstract

Dynamic mechanical measurements for solid films of poly(e-N-benzyloxy-carbonyl-L-lysine) (PCLL) were carried out with torsion pendulum apparatus over a frequency range from 1.0 to 0.003 Hz at various temperatures within its side-chain dispersion region, and the effects of annealing were also examined. Frequency dispersion curves of real and imaginary parts of complex rigidity and loss tangent were superposed onto master curves by performing suitable shifts along the logarithmic frequency axis. The temperature dependence of shift factor aT was well represented by the Williams—Landel—Ferry equation with the universal parameters. The dispersion exhibits some characteristics of the glass transition, as was found for the side-chain dispersions of poly(γ-benzyl L-glutamate) (PBLG), poly(γ-methyl L-glutamate) (PMLG), and their copolymers. The relaxation spectrum for PCLL is considerably sharper than those for PBLG or PMLG. As the temperature of the annealing is increased, the dispersion shifts to higher temperatures (longer times) and the distribution of the relaxation times becomes a little broader.