CELLULOSE-BASED FIBERS FROM LIQUID-CRYSTALLINE SOLUTIONS - SOLUTION PROPERTIES OF CELLULOSE ESTERS

Solutions of cellulose esters with different concentrations in dimethyl acetamide (DMAc) and with different types of substituents, but with nearly constant total degree of substitution and constant molecular weights, were studied in relation to their liquid crystalline solution behavior. Observations made by dynamic mechanical spectrometry and by cross-polarized optical microscopy revealed classical liquid crystalline behavior for all solutions. Critical polymer concentration levels (V(p)c) were observed for all cellulose esters, and these were found to vary with substitution pattern. V(p)c is highest for cellulose acetate and lowest for the cellulose acetate butyrate with maximum degree of butyration. This is opposite to expected behavior based on the classical model by Flory, which predicts an increase in V(p)c with decreasing aspect ratio. Cellulose ester solutions are viscoelastic in nature.