利用流变学方法研究了两性表面活性剂十四烷基磺基甜菜碱(TDAPS)和阴离子表面活性剂十二烷基硫酸钠(SDS)混合体系中蠕虫状胶束的耐盐性能,分析了二价金属离子对蠕虫状胶束微观结构的影响.结果表明,在加入MgCl2和CaCl2使Mg2+和Ca2+总浓度达到0~1900 mg/L的情况下,TDAPS/SDS体系中形成的蠕虫状胶束的粘弹性能和耐剪切能力不仅没有损失而且增强.对静态流变和动态流变结果进一步分析表明体系中同时存在两种可区分尺寸的蠕虫状胶束.加入二价金属离子,体系的微观结构发生了由小尺寸蠕虫状胶束向大尺寸蠕虫状胶束转变,同时,大尺寸蠕虫状胶束线性增长并发生枝化.两性表面活性剂头基上的正电荷中心减小了蠕虫状胶束的反离子结合程度,抑制了线性生长到枝化生长的过程,使体系表现出优异的耐盐性能.
The salt resistance property and microstructure transition induced by divalent metal ion of wormlike micelle formed in mixed zwitterionic(N-tetradecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate,TDAPS) and anionic(sodium dodecyl sulfate,SDS) surfactant system are investigated by rheological meas-urement.It has been found that the viscoelastic and anti-shearing properties of this wormlike micelle system are not reduced but reinforced in the total concentration of Mg2+ and Ca2+ range of 0~1900 mg/L upon adding MgCl2 and CaCl2.A further analysis of the rheolgical measurement results show that two distinct length wormlike micelles coexist in this system.During the addition of divalent metal ion,a transition from small wormlike micelle to large wormlike micelle takes place,and the large wormlike micelle grows linear and branched at the same time.The positive charge on the zwitterionic surfactant headgroup reduces the binding efficiency of the wormlike micelle,and inhibits the microstructure transition,which endows the high salt resistance property of this system.