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采用分子动力学的方法研究了阴离子表面活性剂十六烷基苯磺酸盐在正十六烷-水界面上的聚集结构,研究了苯环在碳氢链上的取代位置对油水界面性质的影响。由界面生成能和界面层厚度的计算结果可知,苯磺酸盐接在十六烷第2个碳上体系从能量上最稳定,界面厚度最大;不同体系的分子占有面积和分子构象参数决定了不同表面活性剂界面单层膜排列情况。研究结果表明,对于较大碳数烷烃,支链烷基苯磺酸盐结构的影响主要来自于尾链的构象排布,苯环的取代位置越靠近碳链端点,分子占有面积越小,在界面上的吸附能力越强。表面活性剂分子的伸展性和有序性的增加使界面排布更紧密,更容易达到低界面张力,利于驱油。
The molecular structure of the anionic surfactant cetyl benzene sulfonate at the n-hexadecane-water interface was studied by molecular dynamics method. The effect of the substitution position of benzene ring on the hydrocarbon chain on the interfacial properties of oil and water influences. From the calculated results of interfacial energy and interfacial layer thickness, it is found that benzene sulfonate is the most energetically stable and has the largest interface thickness on the second carbon of hexadecane. The molecular occupancy and molecular conformational parameters of different systems determine Different surfactant interface monolayer alignment. The results show that the structure of branched alkylbenzene sulfonate mainly comes from the conformational arrangement of the tail chain for larger carbon number alkanes. The closer the position of benzene ring substitution is to the end of the carbon chain, the smaller the occupied area is. The adsorption capacity of the interface is stronger. Surfactant molecules extend the scalability and order to make the interface more closely arranged, easier to achieve low interfacial tension, which will help oil displacement.