Molecular association of polypeptides in concentrated solutions investigated by the electrooptical method: I. Poly-γ-benzyl- l-glutamate—dichloroethane system

Abstract

From the saturation effect of the electric birefringence in PBLG-dichloroethane systems at various concentrations, values of the dipole moment and the optical anisotropy factor were obtained, and the average relaxation time of the rotational diffusion was obtained from the decay process of the birefringence. The dipole moment and the average relaxation time increased remarkably with increasing concentration in the pre-liquid crystal region, whereas the optical anisotropy factor did not. Above a critical concentration the solution became naturally birefringent a week after. During this process noticeable increases of the dipole moment and the average relaxation time were found. In order to make the physical image concrete as to what was happening in the solution, the length distribution functions were derived from the relaxation curves at various conditions. The results strongly suggest that a cooperative growth of the molecular aggregates is the groundwork of the formation of the liquid crystalline phase.