Self-assembly and adsorption of cetyltrimethylammonium bromide and didodecyldimethylammonium bromide surfactants at the mica-water interface.
Self-assembly and adsorption of cetyltrimethylammonium bromide and didodecyldimethylammonium bromide surfactants at the mica-water interface.
复制标题
十六烷基三甲基溴化铵和双十二烷基二甲基溴化铵表面活性剂在云母-水界面的自组装和吸附。
DOI：
10.1039/c9sm01464k
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发表时间：
2019
期刊：
影响因子：
3.4
通讯作者：
Tsagkaropoulou G
中科院分区：
文献类型：
--
作者：
Tsagkaropoulou G
采用分子动力学模拟方法研究了十六烷基三甲基溴化铵（CTAB）和双十二烷基二甲基溴化铵（DDAB）在白云母-水界面上的自组装和吸附。吸附通过离子交换机制发生，其中K+离子被溶液中的有机烷基铵阳离子取代。进行模拟，有和没有表面K+离子，纯水，和水溶液中的表面活性剂。CTAB和DDAB在本体溶液中形成胶束结构，并且在没有表面K+离子的情况下，它们快速吸附并形成双层结构。十六烷基三甲基溴化铵（CTAB）的双层有序性并不完善，与圆柱形胶束的形成存在竞争。另一方面，DDAB形成良好有序的双层结构，最内层显示出较强的取向有序性，最外层更无序。纯水的模拟突出了分子有序性和与云母表面原子的强静电相互作用。使用模拟的散射长度密度分布，结果进行了比较，直接和批判与现有的中子反射率测量。模拟结果与实验结果基本一致，并对云母-水界面的分子尺度有序性产生了新的认识。
The self-assembly and adsorption of the surfactants cetyltrimethylammonium bromide (CTAB) and didodecyldimethylammonium bromide (DDAB) at the muscovite mica–water interface are studied using molecular-dynamics simulations. Adsorption takes place by an ion-exchange mechanism, in which K+ ions are replaced by the organic alkylammonium cations from the solution. Simulations are performed with and without the surface K+ ions, with pure water, and with the surfactants in aqueous solution. CTAB and DDAB form micellar structures in bulk solution, and in the absence of the surface K+ ions, they quickly adsorb and form bilayer structures. The bilayer ordering of CTAB is not perfect, and there is a competition with the formation of cylindrical micelles. DDAB, on the other hand, forms a well-ordered bilayer structure, with the innermost layer showing strong orientational ordering, and the outermost layer being more disordered. The simulations with pure water highlight the molecular ordering and strong electrostatic interactions with the mica-surface atoms. Using simulated scattering length density profiles, the results are compared directly and critically with existing neutron reflectivity measurements. The simulation results are generally consistent with experiments, and yield new insights on the molecular-scale ordering at the mica–water interface.