粗粒化力场分子动力学模拟研究十二烷基硫酸钠(SDS)和十二烷基苯磺酸钠(LAS)在硬水中的协同作用
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- 英文论文题名：Improved Hardness Tolerance of Mixed Anionic Surfactants(Sodium Dodecyl Sulfate(SDS) and Sodium Dodecyl 6-Benzene Sulfonate(LAS))Investigated by Coarse-Grained Molecular Dynamics Simulation
- 论文作者：龚正 ; 孙淮
- 英文论文作者：Zheng Gong ; Huai Sun ; School of Chemistry and Chemical Engineering ; Shanghai Jiao Tong University
- 年：2016
- 作者机构：上海交通大学化学化工学院;
- 论文关键词：阴离子表面活性剂 ; 硬水 ; 沉淀 ; 粗粒化力场 ; 分子动力学模拟
- 会议召开时间：2016-07-01
- 会议录名称：中国化学会第30届学术年会摘要集-第三十一分会：胶体与界面化学
- 语种：中文
- 分类号：TQ649.1
- 学会代码：ZGHY
- 会议名称：中国化学会第30届学术年会-第三十一分会 ; 胶体与界面化学
- 会议地点：中国辽宁大连
- 主办单位：中国化学会
- 学会名称：中国化学会
- 页数：1
- 文件大小：144k
- 原文格式：D
- 会议级别：全国
摘要
SDS和LAS在工业生产和日常生活中有着广泛的应用,通常用作洗涤用品中的有效成分。但是在硬水中,SDS或LAS会与二价阳离子(主要是钙镁离子)生成沉淀,严重削弱它们的洗涤性能。研究报道,相比于SDS或LAS的单组份系统,SDS和LAS的混合物在硬水中不容易形成沉淀。这一现象的机理尚不明确。在这里,我们先以全原子力场为基础,开发了适用于表面活性剂和硬水体系的粗粒化力场。然后使用该力场,直接模拟了不同表面活性剂在氯化钙溶液中的聚集。结果显示,当有钙离子存在时,SDS和LAS的混合物比纯的SDS或LAS聚集要慢,这一模拟结果与实验相符。通过分析模拟轨迹,我们发现SDS和LAS在钙离子存在下的聚集机理不同,哪种机理占主导地位取决于钙离子的分布和钙离子与阴离子表面活性剂头基之间的作用强弱。钙离子会促进SDS或LAS形成碟状胶束。在胶束生长过程中,SDS的胶束倾向于纵向聚集,而LAS倾向于侧向融合。而对于SDS和LAS的混合物,这两种聚集机理都被抑制,因而在硬水中不容易沉淀。
SDS and LAS are the detergents used in daily life.It is known the performance of SDS and LAS are severely inhibited in hard water,because both of them precipitate with divalent ions.The mixture of SDS and LAS is reported to show improved hardness tolerance than pure component system of SDS or LAS.In this work,a coarse-grained force field for SDS/LAS/CaCl_2/water system is developed.Utilizing the force field,we investigate the aggregation mechanism of SDS-LAS mixture in hard water.We find that,the mixture surfactants aggregates slower in the presence of calcium ions than that of pure SDS or LAS system.Two mechanisms,vertical growth and lateral fusion,are found in the aggregation process,and the dominant aggregation mechanism depends on the distribution of calcium ions and the interaction between calcium ions and headgroups.The SDS micelle tends to grow vertically,while LAS micelle prefers lateral fusion.For SDS-LAS mixture,both aggregation mechanisms are inhibited,resulting in the enhanced harness tolerance of mixture system.
SDS and LAS are the detergents used in daily life.It is known the performance of SDS and LAS are severely inhibited in hard water,because both of them precipitate with divalent ions.The mixture of SDS and LAS is reported to show improved hardness tolerance than pure component system of SDS or LAS.In this work,a coarse-grained force field for SDS/LAS/CaCl_2/water system is developed.Utilizing the force field,we investigate the aggregation mechanism of SDS-LAS mixture in hard water.We find that,the mixture surfactants aggregates slower in the presence of calcium ions than that of pure SDS or LAS system.Two mechanisms,vertical growth and lateral fusion,are found in the aggregation process,and the dominant aggregation mechanism depends on the distribution of calcium ions and the interaction between calcium ions and headgroups.The SDS micelle tends to grow vertically,while LAS micelle prefers lateral fusion.For SDS-LAS mixture,both aggregation mechanisms are inhibited,resulting in the enhanced harness tolerance of mixture system.
引文
[1]Shinoda,W.;De Vane,R.;Klein,M.L.Soft Matter 2011,7:6178.