Characterization of curdlan in aqueous sodium hydroxide

Curdlan ((1 --> 3)-beta-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 x 10(4) to 2.0 x 10(6). The observed intrinsic viscosity [eta] 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 [eta] 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. (C) 1997 Elsevier Science Ltd. All rights reserved.