The electrical birefringence of cellulose carbanilate solutions as a function of molecular weight

Abstract

The electron, dynamo-optical and hydrodynamic properties of a series of solutions of fractions of cellulose carbanilate (CC) were studied in dioxane and in ethyl acetate. There was a strong Kerr dispersion effect in an alternating electrical field which indicated a dipole oriented mechanism for electrical birefringence and its relaxation. Comparison of the relaxation periods of these fractions with their molecular weights (mol.wt) and the intrinsic viscosities has led to the conclusion that the mechanism responsible for the Kerr effect is a molecular rotation of the entire molecule in the electrical field (a kinetically rigid molecule). The relaxation period as a function of mol.wt. M has shown that an increase of the latter causes the CC molecular conformations to change from a slightly bent rod to a rigid Gaussian coil. The same conclusion was also reached in the study of the Kerr equilibrium constant K as a function of M. The Kerr effect depends in the Gaussian range (larger M) on the parallel component (relative to the chain) of the dipole moment formed by the CO bond present in the glucoside ring. A considerable part is played in birefringence at small M by the transverse component of monomeric dipoles.