Molecular dynamics simulation of binary betaine and anionic surfactant mixtures at decane - Water interface
Molecular dynamics simulation of binary betaine and anionic surfactant mixtures at decane - Water interface
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二元甜菜碱和阴离子表面活性剂混合物在癸烷-水界面的分子动力学模拟
DOI：
10.1016/j.molliq.2018.06.047
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发表时间：
2018-09-15
影响因子：
6
通讯作者：
Zhao, Sui
中科院分区：
文献类型：
--
作者：
Cai, Hong-Yan;Zhang, Yi;Zhao, Sui
用分子动力学模拟方法研究了甜菜碱与阴离子表面活性剂复配体系在正庚烷-水界面的界面性质。两种甜菜碱为烷基甜菜碱(ASB)和烷基苯磺基甜菜碱(BSB)，三种阴离子表面活性剂分别为十二烷基硫酸钠(SDS)、十二烷基苯磺酸钠(SDBS)和十八烷基磺酸钠(SOS)。从质量密度分布、界面厚度、原子间距和倾斜角等方面考察了甜菜碱与阴离子表面活性剂的协同效应。用原子间距和倾斜角计算了甜菜碱的亲水性尺寸。亲水性尺寸的计算值约为81A(2)，与实验饱和吸附面积和模拟的临界胶束面积大致相等。存在两层阴离子表面活性剂，少量分子与ASB平行，产生竞争吸附。更多的阴离子表面活性剂位于ASB疏水链的裂隙中，形成混合吸附。混合吸附对甜菜碱/阴离子表面活性剂混合物的吸附过程起主导作用。SDBS在油相的分布范围与ASB的分布范围完全相同，说明两种表面活性剂的疏水链长基本一致。通过比较混合吸附层上的甜菜碱数和阴离子表面活性剂数，可以定量计算界面的致密性。模拟的界面密实度与实验的界面张力很好地吻合，这可能代表着对不同甜菜碱混合物进行比较的可靠评价标准的发现。表面活性剂的亲水-亲油平衡和亲水-疏水结构的一致性都会影响界面性质。在分子水平上完善了表面活性剂混合吸附的机理，对提高采收率具有重要意义。(C)2018爱思唯尔B.V.保留所有权利。
The interfacial properties of binary betaine and anionic surfactant mixtures at decane-water interface have been studied via molecular dynamics simulations. Two betaines chosen are alkyl sulfobetaine (ASB) and alkylbenzene sulfobetaine (BSB), while three anionic surfactants chosen are sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfonate (SDBS) and sodium octadecyl sulfonate (SOS), respectively. The synergistic influences between betaines and anionic surfactants are explored using mass density profile, interfacial thickness, atomic spacing and oblique angle. Hydrophilic size of betaine has been calculated through atomic spacing and oblique angle. The calculated value of hydrophilic size is about 81 A(2), which is approximately equal to experimental saturated adsorption area and simulated critical micelle area. Two anionic surfactant layers exist, a small amount of molecules are paralleled with ASB to generate competitive adsorption. More anionic surfactants are located in the cracks of ASB hydrophobic chains to form mixed adsorption. Mixed adsorption dominates surfactant adsorbent process for betaine/anionic surfactant mixtures. SDBS distribution range is exactly same as ASB range at the oil phase, which implies the consistent of hydrophobic chain lengths between above two surfactants. Interfacial compactness can be quantitative calculated by comparing betaine number and anionic surfactant number at mixed adsorbent layer. Simulated interfacial compactness perfectly corresponds with experimental interfacial tension, which may stand for the discovery about reliable evaluation criteria of comparing different betaine mixtures. Both surfactant hydrophilic-lipophilic balance and consistency of hydrophilic-hydrophobic structure can affect interfacial properties. The mechanism about surfactant mixed adsorption is also perfected at a molecular level, which is important for the enhanced oil recovery processes. (C) 2018 Elsevier B.V. All rights reserved.