Shrestha Lok Kumar, Sato Takaaki, Aramaki Kenji
Graduate School of Environment and Information Sciences, Yokohama National University, Tokiwadai 79-7, Yokohama 240-8501, Japan.
J Phys Chem B. 2007 Feb 22;111(7):1664-71. doi: 10.1021/jp067546d. Epub 2007 Jan 26.
We have investigated the self-organization structures of diglycerol monomyristate (DGM) in different types of organic solvents. Study of phase behavior shows the presence of solid at lower temperature, and upon increasing temperature, the solid phase transforms to lamellar liquid crystal (L(alpha)) phase in the surfactant axis in all the DGM/oil systems. In the dilute regions, however, the dispersion of the solid or L(alpha) phase is observed, depending on the solvent and temperature. At higher temperatures, the L(alpha) phase melts to the isotropic reverse micellar solution phase. GIFT analysis of small-angle X-ray scattering data supported by a complementary modeling method have unambiguously shown that the structure of the DGM reverse aggregates can flexibly be controlled by optimizing the fundamental properties of solvent oils. In aromatic oils, the observed moderate micellar elongation is almost solely governed by the polarity of the aromatic ring, the length of the hydrocarbon side chain group showing no drastic effect. In contrast, when the solvent is replaced with linear-chain hydrocarbon oils, the drastic effects depending on the chain length emerge; by gradually increasing the length from decane to hexadecane, the long cylindrical particles in decane are finally transformed into planar aggregates, whose mechanism may be explained in terms of the transfer free energy of the diglycerol moiety from the hydrophilic environment to the hydrocarbon oils with a different chain length. We have also systematically examined the effects of temperature, the surfactant concentration, and added water.
我们研究了甘油单肉豆蔻酸酯(DGM)在不同类型有机溶剂中的自组织结构。相行为研究表明,在较低温度下存在固体,随着温度升高,在所有DGM/油体系中,固相会在表面活性剂轴向上转变为层状液晶(L(α))相。然而,在稀溶液区域,根据溶剂和温度的不同,会观察到固体或L(α)相的分散情况。在较高温度下,L(α)相会熔化为各向同性的反胶束溶液相。通过互补建模方法支持的小角X射线散射数据的GIFT分析明确表明,通过优化溶剂油的基本性质,可以灵活地控制DGM反聚集体的结构。在芳烃油中,观察到的适度胶束伸长几乎完全由芳环的极性决定,烃侧链基团的长度没有显著影响。相比之下,当溶剂被直链烃油取代时,会出现取决于链长的显著影响;从癸烷到十六烷逐渐增加链长,癸烷中的长圆柱形颗粒最终会转变为平面聚集体,其机制可以用甘油二酯部分从亲水环境转移到不同链长的烃油中的转移自由能来解释。我们还系统地研究了温度、表面活性剂浓度和添加水的影响。