Characterization of curdlan in aqueous sodium hydroxide

Abstract

Curdlan ((1 → 3)-β-D-glucan) was found to be fractionated through liquid—liquid phase equilibrium with the mixture dimethyl sulfoxide + lithium chloride as a solvent and acetone as a precipitant. Light scattering and viscosity measurements were made on solutions of fractionated samples in 0.3 M NaOH in the range of the molecular weight M w, from 5.3 × 10 4 to 2.0 × 10 6. The observed intrinsic viscosity [η] was analysed by the Yamakawa—Fujii—Yoshizaki theory of a wormlike chain, and the persistence length, molecular weight per unit contour length and molecular diameter were determined roughly as 6.8 nm, 890 g nm −1 and 1.1 nm, respectively. These molecular parameters represented the molecular weight dependence of [η] and the mean-square radius of gyration 〈 s 2〉 z , reasonably indicating an effect of the excluded volume at large M w. Detailed behaviour of curdlan in 0.3 M NaOH could not be revealed on account of a large uncertainty caused by microgel aggregates in the light scattering measurements.