Ca^(2+)介导的月桂酰甲基牛磺酸钠相行为研究

Study on the phase behavior of sodium lauroyl methyltaurate mediated by Ca^(2+)

为探究高价无机盐对阴离子表面活性剂月桂酰甲基牛磺酸钠(SMLT)溶液的表面活性和相行为的影响,考察了Ca^(2+)浓度对SMLT溶液的表面张力和不同SMLT/Ca^(2+)摩尔比对SMLT/水二元体系的相行为影响。结果表明,加入适量的Ca^(2+)对其表面活性影响显著,当Ca^(2+)浓度从0增加至0.1 mol/L时,cmc从8.0×10^(-3)mol/L降至8.0×10^(-4)mol/L,γ_(cmc)从36.00 mN/m降至31.45 mN/m。同时,在SMLT溶液中加入Ca^(2+),SMLT/水体系的二元相图出现胶束溶液相区、蠕虫胶束相区、六角束液晶相区、层状液晶相区和胶束-晶体相区,原有的双水相区消失,胶束-晶体区变大。在考察Ca^(2+)浓度对SMLT溶液黏度的影响时,发现当SMLT/Ca^(2+)的摩尔比为1时,SMLT溶液增黏效果明显,摩尔比为0.6时溶液析出固体。选择质量分数为20%的SMLT溶液进行流变性能测定,根据样品流变曲线,发现其具有剪切变稀的现象,冷冻透射电镜显示有蠕虫胶束的形成。

The effects of high-valent inorganic salts on the surface activity and phase behavior of anionic surfactant sodium lauroyl methyl taurate(or sodium methyl lauroyl taurate,SMLT)were studied.The effects of Ca^(2+)concentration on the surface tension of SMLT solution and the effects of different SMLT/Ca^(2+)molar ratios on the phase behavior of SMLT in water were investigated.The results showed that the addition of an appropriate amount of Ca^(2+)had significant impact on the surface activity.When the Ca^(2+)concentration was increased from 0 to 0.1 mol/L,the cmc decreased from 8.0×10^(-3) mol/L to 8.0×10^(-4) mol/L,and theγ_(cmc) decreased from 36.00 mN/m to 31.45 mN/m.Meanwhile,by adding Ca^(2+)to the SMLT solution,the binary phase diagram of the SMLT/water system showed phase regions of micellar solution region,wormlike micelle region,hexagonal liquid crystal region,lamellar liquid crystal region,and micellecrystal region.The original aqueous two-phase region disappeared,and the micelle-crystal region became larger.When examining the effect of Ca^(2+)concentration on the viscosity of SMLT solution,it was found that,with a molar ratio of SMLT/Ca^(2+)of 1,the viscosity was significantly increased,while at a molar ratio of 0.6,solid precipitated from the solution.An SMLT solution at mass fraction of 20%was selected for measurement of rheological performance.According to the rheological curve of the sample,a phenomenon of shear thinning was observed,and the formation of wormlike micelles was observed by cryogenic transmission electron microscopy.