阳离子纤维素-十二烷基苯磺酸钠的拟聚阴离子研究

采用浊度法、 表面张力法、 zeta电位法和毛细管电泳法(CE)研究了典型的阳离子纤维素(JR400)与典型的阴离子表面活性剂十二烷基苯磺酸钠(SDBS)之间的缔合作用. 浊度法和zeta电位法实验结果表明, 在等电区附近产生的沉淀区随JR400浓度减小而变窄, 加入过量SDBS后沉淀消失, 而且发现阳离子纤维素同系物的分子量和取代度对结果的影响较小. 表面张力法实验结果显示, 该类复合体系的表面张力曲线表观上与典型“中性聚合物-阴离子表面活性剂”体系相似, 具有3个拐点(但第二拐点易被沉淀区覆盖)且SDBS与阳离子纤维素间形成缔合物. zeta电位法实验结果表明, 沉淀区前少量SDBS存在时该缔合物具有正电位, 因而维持聚阳离子特性; 沉淀区后过量SDBS存在时该缔合物具有负电位, CE分析进一步证明其为拟聚阴离子. 上述实验结果和结论对研究该类复合体系具有较大理论意义和实用价值.

Investigation on Pseudo-polyanions of Cationic Cellulose-Sodium Dodecylbenzenesulfonate†

The complexation between typical cationic cellulose(JR400) and a typical anionic surfactant sodium dodecylbenzenesulfonate(SDBS) in aqueous solution was studied by nephelometry, tensiometry, zeta potential method and capillary electrophoresis(CE) in this paper. The turbidity and the zeta potential results show that precipitation zone(PZ) appears near to the isoelectric zone and shrinks with the declined concentration of JR400, and sediment disappears when SDBS in large excess, in addition to being less influenced by molecular weight and substitution degree of the cationic celluloses. The tensiometry results show that there are three critical concentration thresholds though the second critical concentration is commonly overlapped by PZ, which indicates the formation of complexes between SDBS and the polycations similar with “neutral polymer-anionic surfactant” systems. The zeta potential results show that the complexes formed ahead of PZ have the positive zeta potential so that keep the polycation properties, while behind the zone the negative in large excess of SDBS, and the latter is confirmed by CE being pseudo-polyanions. These experimental results and conclusions have great theoretical significance and practical value for studies of polycation-anionic surfactant systems.