New results concerning the behavior of cellulose acetate in solutions and films by means of CD measurements

Cellulose acetate (DS = 2.45) was extensively investigated by Circular Dich roism (CD) in acetonitrile and dioxane. Wefolrnd great differences between the CD spectra of a 1 wt % acetonitrile solution and the corresponding diox ane solution of cellulose acetate (CA) indicating that the macromolecules e xist in those solutions in different molecular arrangements (e.g., persiste nce length solvatation shell). The resulting morphologies could be transfor med reversibly into each other, as we found by measuring the CA in mixtures of both solvents. Solid CA films show discernible CD spectra depending on the solvent they were evaporated from. In this way, we prepared solid films of the same polysaccharide owning different chiral properties. Furthermore , changes in the spectra occurred with increasing CA concentration. Basing upon our findings, some general statements concerning the polymer behavior of CA are possible. (C) 1999 John Wiley & Sons, Inc.