Department of Applied Chemistry, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan.
J Chem Phys. 2012 Sep 7;137(9):094902. doi: 10.1063/1.4747491.
Free energy of transfer of methylamine, octylamine, methanol, and octanol from water phase to sodium dodecyl sulfate (SDS) micelle has been calculated using thermodynamic integration method combined with molecular dynamics calculations. Together with the results for alkanes obtained in our previous study [K. Fujimoto, N. Yoshii, and S. Okazaki, J. Chem. Phys. 133, 074511 (2010)], the effect of polar group on the partition of hydrophilic solutes between water phase and the micelle has been investigated in detail at a molecular level. The calculations showed that the molecules with octyl group are more stable in the SDS micelle than in the water phase due to their hydrophobicity of long alkyl chain. In contrast, methanol and methylamine are stable in the water phase as well as in the micelle because of their high hydrophilicity. The spatial distribution of methylamine, octylamine, methanol, and octanol has also been evaluated as a function of the distance, R, from the center of mass of SDS micelle to the solutes. The distribution shows that the methylamine molecule is adsorbed on the SDS micelle surface, while the methanol molecule is delocalized among the whole system, i.e., in the water phase, on the surface of the micelle, and in the hydrophobic core of the micelle. The octylamine and octanol molecules are solubilized in the SDS micelle with palisade layer structure and are not found in the water phase.
已使用热力学积分法结合分子动力学计算，计算了甲胺、辛胺、甲醇和辛醇从水相向十二烷基硫酸钠（SDS）胶束转移的自由能。结合我们之前在烷烃研究中的结果[K. Fujimoto、N. Yoshii 和 S. Okazaki，J. Chem. Phys. 133, 074511（2010）]，从分子水平详细研究了极性基团对亲水分子在水相和胶束之间分配的影响。计算表明，由于长烷基链的疏水性，具有辛基的分子在 SDS 胶束中比在水相中更稳定。相比之下，甲醇和甲胺由于其高亲水性，在水相和胶束中都很稳定。还评估了甲胺、辛胺、甲醇和辛醇的空间分布作为距 SDS 胶束质心的距离，R 的函数。分布表明，甲胺分子被吸附在 SDS 胶束表面，而甲醇分子在整个体系中弥散，即在水相、胶束表面和胶束的疏水核中。辛胺和辛醇分子溶解在具有栅栏层结构的 SDS 胶束中，而不在水相中发现。
