DYNAMIC BIREFRINGENCE OF CELLULOSE ACETOBENZOATE SOLUTIONS

Dynamic bifringence of cellulose acetobenzoate solutions in dioxane at 21-degrees has been studied for the range of samples and fractions of close degrees of substitution (245 towards benzoic acid and 55 towards acetic acid) in the 200-fold MM range. Reduced birefringence [n]/[eta] increases with increase of MM for M less-than-or-equal-to 2.10(5) and doesnot depend on MM for M > 2.10(5). The experimentally found dependence of [n]/[eta] on MM is characteristic for rigid polymers and is described by the birefringence theory for the model of the kinetically rigid worm-like chain. The value of the optical anisotropy of the statistical Kuhn segment alpha-1-alpha-2 = 1085.10(-25) cm2. Using the value of the Kuhn segment A = 210.10(-8) cm found earlier for this polymer the value of the optical anisotropy of the chain length unity has been determined: beta-L = (5.2 +/- 0.3).10(-17) cm2. Optical characteristics of cellulose acetobenzoate molecules are compared with corresponding ones of cellulose carbanylate.