Bola反离子诱导的高粘弹十六烷基硫酸钠蠕虫胶束溶液

利用稳态和频率扫描研究了十六烷基硫酸钠(SHS)与Bola盐(N,N’-双乙基二甲基-α,ω-乙烷溴化铵(Bola2Et)或N,N’-三甲基-α,ω-丁烷溴化铵(Bola4))混合体系的流变行为.实验结果表明两个体系均在45℃时形成了长蠕虫胶束,溶液呈现出高粘弹性,尤其是SHS/Bola2Et溶液表现出很高的弹性,零剪接粘度高达2520Pa’s,表观上呈现胶状.这些结果归因于在Bola反离子诱导下,表面活性剂SHS与Bola反离子形成了静电吸引的2:1结构复合物.由于这两个Bola反离子的联接链长度均短于季铵离子的静电平衡距离,因此形成的复合物在形状上有利于蠕虫胶束生成.作为对比,添加简单的四甲基铵反离子无法诱导SHS形成蠕虫胶束,溶液仅呈现低粘度.

Highly Viscoelastic Worm-Like Micelle Solution of Sodium Hexadecyl Sulfate Induced by Bolaform Counterions

The rheological behaviors of mixed aqueous solutions of sodium hexadecyl sulfate(SHS)and a bolaform salt,either N,N’-ethanediyl-α,ω-bis(ethyldimethylammonium bromide)(Bola2Et)or N,N’-propanediyl-α,ω-bis(trimethylammonium bromide)(Bola4),were investigated by steady-state and frequency-sweep measurements.The results showed that long worm-like micelles were formed in both systems at 45℃,and the solutions exhibited high viscoelasticities,especially the SHS/Bola2Et system in which the solution had very high elasticity.The zero-shear viscosity of SHS/Bola2Et was as high as 2520 Pa·s,and the system was gel-like.These results were attributed to the formation of 2:1 complexes by electrostatic attraction.Since the spacers of both Bola counterions were shorter than the distance between quaternary ammonium ions under electrostatic equilibrium,the generated complex in shape favored formation of worm-like micelles.In comparison,it was difficult to induce SHS to form worm-like micelles by the addition of tetramethylammonium counterions,and the solution exhibited low viscosity.