The rise process of the electric birefringence of poly-γ-benzyl-l-glutamate at high fields

Abstract

The rise process, steady-state and decay process of the birefringence of poly-γ-benzyl-l-glutamate solutions under the action of a rectangular pulse have been studied at 25 °C over a wide range of field strength of 1.5×103 to 3×104V/cm. The solvent used was a dichloroethane-dimethylformamide mixture of the volume ratio 99∶1. From the decay process the average relaxation time extrapolated to zero concentration and the corresponding rotational diffusion constant were determined. The apparent dipole moment and the optical anisotropy factor were obtained from the field strength dependence of steady-state birefringence. The rise process was analyzed according to our theory which holds for arbitrary high field strength in the initial stage. The Δn(t)/t versus t curves for various field strengths were found to be linear in the initial stage and pass through the origin. Thus, it was concluded that the electrical orientation of poly-γ-benzyl-l-glutamate in solution is due primarily to the permanent dipole moment. Furthermore, the value of the apparent permanent dipole moment obtained from the rise process was compared with that obtained from the steadystate birefringence.