A molecular dynamics study of local pressures and interfacial tensions of SDS micelles and dodecane droplets in water.
A molecular dynamics study of local pressures and interfacial tensions of SDS micelles and dodecane droplets in water.
复制标题
水中 SDS 胶束和十二烷液滴的局部压力和界面张力的分子动力学研究。
DOI：
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发表时间：
2016
影响因子：
4.4
通讯作者：
S. Okazaki
中科院分区：
文献类型：
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作者：
Masahiro Kitabata;K. Fujimoto;N. Yoshii;S. Okazaki
为了获得局部压力张量PN(R)和PT(R)的径向（法向）和侧向（横向）分量，以及胶束的界面张力，对球形十二烷基硫酸钠（SDS）胶束进行了分子动力学（MD）计算。利用Irving-Kirkwood公式计算了局部压力张量作为径向距离R的函数。对水中的正十二烷液滴也进行了类似的MD计算，以比较局部压力和界面张力值与胶束的差异。SDS胶束和十二烷液滴的界面张力分别为20±5和44±10 mN/m。SDS胶束和十二烷液滴由于界面张力产生的多余自由能分别为340和1331 kJ/mol。用亲水性基团覆盖胶束的疏水核，胶束的稳定性为991 kJ/mol。十二烷液滴的界面张力很大，这是由于PN(R) - PT(R)在所有R值下均为零或正值造成的，而SDS胶束中的界面张力较小，则是由于在很大的R范围内PN(R) - PT(R)值为负值造成的。油滴内外压差及其界面张力很好地满足拉普拉斯方程。然而，SDS胶束的疏水核与液态烷烃有很大的不同，SDS胶束不符合拉普拉斯图。将界面张力分解为各种相互作用的贡献，发现带电基团和极性基团之间的相互作用主导了SDS胶束的界面张力。胶束表面的正静电电位（1.3 V）和油滴表面的负静电电位（-0.15 V）对界面张力的贡献分别为19和0.5 mN/m。因此，SDS胶束的界面张力是由静电相互作用产生的，与十二烷液滴相反。
To obtain the radial (normal) and lateral (transverse) components of the local pressure tensor, PN(R) and PT(R), respectively, and the interfacial tension of micelles, molecular dynamics (MD) calculations were performed for spherical sodium dodecyl sulfate (SDS) micelles. The local pressure tensor was calculated as a function of radial distance R using the Irving-Kirkwood formula. Similar MD calculations were also carried out for an n-dodecane droplet in water to compare the differences in the local pressure and interfacial tension values with those of the micelles. The calculated interfacial tensions were 20 ± 5 and 44 ± 10 mN/m for the SDS micelles and dodecane droplets, respectively. The excess free energies due to the interfacial tension were 340 and 1331 kJ/mol for the SDS micelle and dodecane droplet, respectively. The micelles are stabilized by 991 kJ/mol by covering their hydrophobic cores with hydrophilic groups. The dodecane droplet has a large interfacial tension caused by the zero or positive values of PN(R) - PT(R) at all values of R. In contrast, the small interfacial tension in the SDS micelles comes from the negative PN(R) - PT(R) values over a wide range of R. The pressure difference between the inside and outside of the oil droplet and its interfacial tension well satisfies the Laplace equation. However, the hydrophobic core of the SDS micelle is quite different from the liquid alkane, and the SDS micelles do not follow Laplace's picture. Decomposing the interfacial tension into contributions from various interactions, it is found that those between charged and polar groups dominate the interfacial tension of the SDS micelles. The positive electrostatic potential (1.3 V) on the micelle surface and the negative potential (-0.15 V) on the oil droplet contribute to the interfacial tensions by 19 and 0.5 mN/m, respectively. Thus, the interfacial tension of the SDS micelles is produced by electrostatic interactions, in contrast to the dodecane droplet.
影响因子：
3.4
作者：
Gullingsrud, J;Schulten, K
通讯作者：
Schulten, K