Viscosity Behaviors of Chinese Lacquer Polysaccharide in Aqueous Solutions

Abstract

A Chinese lacquer polysaccharide is an acidic polysaccharide and has a 1, 3-β linked D-galactopyranosidic main chain having complex branches with 4-O-methyl-β-D-glucuronic acid in the terminal. The viscosity of the polysaccharide was measured at 30 ± 0.05°C in water and NaCl solutions. In deionized water, the reduced viscosity increased rapidly with decreasing concentration of polysaccharide, indicating the behavior due to acidic polysaccharides. Dilute NaCl solutions (1.0×10^-4 N and 2.0×10^-4N) produced a maximum in the viscosity curve. In the NaCl solutions between 2.0×10^-3 N and 1 N, the reduced viscosity decreased linearly with decreasing polysaccharide concentrations. It was found that the lacquer polysaccharide had the lowest reduced viscosity in 0.5 N NaCl solution. In high concentrated NaCl solutions more than 1 N, it was revealed that the reduced viscosity increased gradually with increasing NaCl concentrations, suggesting that the counter cation, Na⁺, penetrated into the branches to expand the polysaccharide molecules. The intrinsic viscosity [η] in 0.5 NNaCl solution which provided the lowest reduced viscosity was calculated to be 0.085dl/g by extrapolating to the zero concentration of polysaccharide. In deionized water, the [η] was calculated by the Fuoss linearization to be 0.65dl/g. It was found that the lacquer polysaccharide provided the specific viscosity behaviors in aqueous solutions originated from the complex branched structure.