ジェラン水溶液の粘度に及ぼすアルカリ金属塩の影響

抄録

Effects of alkaline metal salts on zero-shear viscosity (η₀) of gellan aqueous solutions were investigated. The temperature (T) dependence curves of η₀ showed a steep change due to the coil-helix transition of the gellan molecules. The transition temperature (T_Tr) depended on the salt concentration while it was independent of the cationic species. At temperatures higher than T_Tr, η₀ decreased with increasing salt concentration. At temperatures lower than T_Tr, T-η₀ curves at various salt concentrations produced a kind of envelope corresponding to the T-η₀ curve for gellan with double-helical conformation. The addition of alkaline salts enhanced the aggregate formation at temperatures lower than T_Tr, and the efficiency for the aggregate formation depended on the cationic species used. At a fixed salt concentration, the degree of aggregation increased in the order of Cs ^{+>Rb+>K+>Na +} >Li. Defining the temperature at which the double helices start to aggregate as T_a, both T_Tr and T_a were not affected by the type of halogens, Cl ^{−, Br− and I−}.