Rosen Milton J, Wang Hongzhuang, Shen Pingping, Zhu Youyi
Surfactant Research Institute, Brooklyn College of the City University of New York, 2900 Bedford Avenue, Brooklyn, NY 11210, USA.
Langmuir. 2005 Apr 26;21(9):3749-56. doi: 10.1021/la0400959.
The interfacial tension (IFT) between alkanes and several individual surfactants and their mixtures has been investigated, using three kinds of alkyl hydrocarbons: decane, dodecane, and tetradecane. For individual and mixed surfactant systems, critical micelle concentrations and areas per molecule at the hydrocarbon-aqueous solution interface were calculated; for the mixed surfactant systems, betasigma(LL), the molecular interaction parameter at the hydrocarbon-aqueous solution interface, and beta(M), the molecular interaction parameter in mixed micelle formation, were calculated. It was found that IFT in the 10(-3) mN/m (ultralow) range can be obtained at surfactant concentrations below 0.05 wt % and even at concentrations below 0.01 wt %, when mixtures of certain surfactants are used at the proper ratio. Surfactants with branched-chain alkyl groups show a much better IFT reduction effectiveness than those with straight-chain alkyl groups. Contrary to what has been observed at the air-aqueous solution surface, mixtures of two homologues with two hydrophobic groups show significant molecular interactions, with both betasigma(LL) and beta(M) having negative values in the 4-5 range in some cases, with the betasigma(LL) value more negative than beta(M). The relationship between micellar shape and ultralow IFT was investigated by calculating the critical packing parameter of the surfactants. It was found that ultralow IFT between the surfactant mixtures and the three hydrocarbons investigated could reach ultralow (<10(-2) mN/m) values when the critical packing parameter is very close to 1.
使用三种烷基烃（癸烷、十二烷和十四烷）研究了烷烃与几种单一表面活性剂及其混合物之间的界面张力（IFT）。对于单一和混合表面活性剂体系，计算了烃 - 水溶液界面处的临界胶束浓度和每个分子的面积；对于混合表面活性剂体系，计算了烃 - 水溶液界面处的分子相互作用参数betasigma(LL)以及混合胶束形成中的分子相互作用参数beta(M)。研究发现，当以适当比例使用某些表面活性剂混合物时，在低于0.05 wt%甚至低于0.01 wt%的表面活性剂浓度下，可获得10⁻³ mN/m（超低）范围内的IFT。具有支链烷基的表面活性剂比具有直链烷基的表面活性剂表现出更好的IFT降低效果。与在空气 - 水溶液表面观察到的情况相反，具有两个疏水基团的两种同系物的混合物表现出显著的分子相互作用，在某些情况下，betasigma(LL)和beta(M)的值均为4 - 5范围内的负值，且betasigma(LL)值比beta(M)更负。通过计算表面活性剂的临界堆积参数，研究了胶束形状与超低IFT之间的关系。研究发现，当临界堆积参数非常接近1时，表面活性剂混合物与所研究的三种烃之间的超低IFT可达到超低（<10⁻² mN/m）值。
