Anisotropy of turbidity and elastic constants of liquid-crystalline polypeptide solutions

Abstract

The light scattering method was utilized to measure the anisotropy of turbidity and to determine elastic constants K 1, K 2 and K 3 in lyotropic solutions of poly(γ-benzyl- l-glutamate) (PBLG). Because of surface-induced orientation of the PBLG molecules, one of the turbidity components showed unexpectedly large values. The order of magnitude of the evaluated elastic constants was within the 10 −7–10 −9 dyn range, and the characteristic anisotropy trend was K 1≥ K 3≥ K 2. The elastic constants correlated with molecular weight and concentration of the polymer, and were also affected by the solvent type. The dependence of the elastic constants was affected by the solvent. Correlation of K 1 and K 1 K 3 with molecular weight was in qualitative agreement with the polymer chain flexibility model.