The Circular Dichroism of Cholesteric Cellulose Acetate Solutions; Dependence on Molecular Weight

Abstract

Concentrated solutions of cellulose acetate in trifluoroacetic acid are cholesteric liquid crystals. The circular dichroism of solutions of two samples of cellulose acetate of different molecular weights has been examined. We found that under the same conditions of temperature and polymer concentration by weights the solutions of the higher molecular weight polymer gave circular dichroism peaks at higher wavelength and of higher intensity and are presumably more highly ordered. Solutions containing mixtures of polymer chains of two different lengths gave a single circular dichroism peak which occurred at a wavelength intermediate between those corresponding to the two polymer species. The intensity of the peak was, however, considerably reduced, in some instances being lower than that which would have been given by either component taken on its own.