Liquid crystalline solutions of cellulose acetate in phosphoric acid

The influence has been studied of both the acid strength of phosphoric acid and the degree of substitution of cellulose acetate on the formation of an anisotropic phase. The solvent composition is expressed as a P2O5 concentr ation. It was found that the clearing temperature increases strongly with d ecreasing amount of water in the solvent. The influence of the degree of su bstitution (DS) was studied on a series of samples with a DS ranging from 0 .23 to 2.89. It was found that over the entire range good solubility occurr ed in anhydrous phosphoric acid. The DS hardly affected the clearing temper ature in the process of dissolving a constant number density of polymer cha ins. However, the birefringence of the solution was strongly influenced by the DS, due to the intrinsic birefringence of the polymer chains. (C) 2001 Elsevier Science Ltd. All rights reserved.