Abstract Gellan is an anionic bacterial polysaccharide, which in aqueous solution dissociates into a charged gellan polymer molecule containing carboxyl ions and counter ions and forms thermoreversible gel under appropriate conditions. In this study, we investigated the effect of polymer concentration, the concentration of added monovalent metallic ion, and temperature on the DC electrical conductivity of the gellan. Results suggest that the DC conductivity decreases with the increasing polymer concentrations and the added monovalent metallic ions. Such a decrease in DC conductivity can be attributed to the reduction of the mobility of counter ions due to the increase in the crosslinking density of the gellan network. DC conductivity of gellan gels was increased with temperature, which is interpreted as the dissolution of physically cross-linked networks, thus increasing the mobility of counter ions. The behavior of temperature variation of DC electrical conductivity reveals an abrupt change at a specific temperature, which can be considered a way to determine the gel point or sol–gel transition temperature T c of this thermoreversible biopolymer gel. This result agrees with that of rheological measurements where the viscosity showed a similar trend with temperature and diverges to infinity at the temperature close to T c.

中文翻译：

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从直流电导率测定结冷胶生物聚合物凝胶的凝胶点

摘要 结冷胶是一种阴离子细菌多糖，在水溶液中可解离成带电荷的结冷胶聚合物分子，其中含有羧基离子和抗衡离子，并在适当条件下形成热可逆凝胶。在这项研究中，我们研究了聚合物浓度、添加的单价金属离子浓度和温度对结冷胶直流电导率的影响。结果表明直流电导率随着聚合物浓度的增加和添加的单价金属离子而降低。DC 电导率的这种降低可归因于由于结冷胶网络的交联密度增加而导致反离子迁移率的降低。结冷胶的直流电导率随温度升高，这被解释为物理交联网络的溶解，从而增加了反离子的迁移率。DC电导率的温度变化行为揭示了在特定温度下的突然变化，这可以被认为是确定这种热可逆生物聚合物凝胶的凝胶点或溶胶-凝胶转变温度T c 的一种方式。该结果与流变测量的结果一致，其中粘度随温度显示出类似的趋势，并在接近 T c 的温度下发散到无穷大。这可以被认为是一种确定这种热可逆生物聚合物凝胶的凝胶点或溶胶-凝胶转变温度 Tc 的方法。该结果与流变测量的结果一致，其中粘度随温度显示出类似的趋势，并在接近 T c 的温度下发散到无穷大。这可以被认为是一种确定这种热可逆生物聚合物凝胶的凝胶点或溶胶-凝胶转变温度 Tc 的方法。该结果与流变测量的结果一致，其中粘度随温度显示出类似的趋势，并在接近 T c 的温度下发散到无穷大。