The effect of dichloroacetic acid on the electric and hydrodynamic properties of poly-γ-benzyl-L-glutamate in solution

Abstract

The electric birefringence of poly-γ-benzyl-Irglutamate in ethylene dichloride-dichloroacetic acid mixtures of various compositions and ethylene dichloride-dimethyl-formamide mixtures (99.8:0.2 and 98:2 by volume) has been measured over a wide range of field strengths by use of the rectangular pulse technique. The apparent permanent dipole moment and the optical anisotropy factor were obtained from the field strength dependence of the steady-state birefringence, and the average relaxation time was obtained from the decay curve of birefringence. In addition, the viscosity of the solutions has been measured at low concentrations of dichloroacetic acid or dimethylformamide. The experimental results suggest that the first addition of dichloroacetic acid gives rise to dissociation of aggregates, protonation of terminal amide groups and change in the average orientation of side chains, and further addition of dichloroacetic acid results in introduction of some breaks in the helix backbone. The most important contribution to the initial abrupt drop of the specific Kerr constant comes from the protonation of terminal amide groups.