Dilute solution properties of water-soluble incompletely substituted cellulose acetate

Abstract

Water-soluble incompletely substituted cellulose acetate (CA) was synthesized by the hydrolysis of cellulose diacetate with hydrochloric acid. CA having a degree of substitution DS between 0.39 and 0.81 was water-soluble. The CA (DS=0.49) whole polymer was fractionated into 15 parts, using water-methanol as the solvent-nonsolvent by the successive solution method. The CA(DS=0.49) polymer was soluble in highly polar organic solvents. Solution viscosity, light scattering, and membrane osmometry measurements were performed at 25»C on these fractions in N, N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), water, and formamide. The fractions had ratios of weight-to-number-average molecular weight Mn/Mn of approximately 1.3, independent of Mw. The following relations between limiting viscosity number [॑], z-average radius of gyration z1/2 and Mw were obtained: [॑]=0.19 Mw0.60 (cm3 g-1) and z1/2=0.50*10-8 Mw0.52 (cm) in DMAc at 25»C. Flory's viscosity parameter ऴ in DMAc was (1.82-2.18)*1023, showing a small molecular weight dependence. The short-range interaction parameter A was estimated thermodynamically as 1.33*10-8 (cm) in DMAc and the conformation parameter σ found to be 2.29. The effect of DS on the molecular characteristics of cellulose acetate is discussed. © 1981 The Society of Polymer Science, Japan.