固体表面选择性吸附及表面活性剂分子自组装体系中的分子动力学模拟

发布时间：2018-02-10 09:54

本文关键词： 自组装膜(SAM) 定位沉积拉伸分子动力学伞形取样表面活性剂分子模拟自组装　出处：《聊城大学》2017年硕士论文　论文类型：学位论文

【摘要】：吸附、沉积、聚集是大自然当中存在的物理现象。微纳尺度有机发光小分子定位沉积形成的图案在众多领域有广泛的应用,因此表面图案的构筑已成为研究热点。表面活性剂由于其独特的双亲性质,在溶液中它们可以形成多种不同形状的聚集体,使得这类化合物在生产生活中有广泛的应用。采用分子模拟的方法研究这些物理现象,从分子层面上揭示这些过程发生的机理,对我们理解和应用一些新型的材料有巨大的指导意义。本论文主要工作如下:(1)采用平衡分子动力学和拉伸分子动力学模拟方法研究了模板诱导有机发光小分子3(5)-(9-蒽基)吡唑(ANP)在自组装膜上的选择性沉积,并利用伞形取样方法和加权柱状图分析法计算了沉积过程的均力势。模拟中以二氧化硅为底板分别构筑两种不同密度的烷烃链自组装膜模板,即低密度的液体扩展相和高密度的液体压缩相。平衡分子动力学结果显示:ANP分子容易沉积至低密度的液体扩展相中,难以沉积至高密度的液体压缩相中。拉伸分子动力学结果表明:当ANP分子沉积至液体压缩相表面时,在进入烷烃膜时遇到较大阻力,因而不易进入到烷烃链单层膜中;而ANP分子在进入液体扩展相的过程中受到的阻力较小。通过比较这两种不同密度自组装膜与ANP分子之间的结合自由能,发现ANP分子进入液体压缩相的能垒较高,而ANP分子与液体扩展相结合更加稳定,导致有机发光小分子在不同密度的模板上具有选择吸附性。(2)采用分子动力学模拟方法探讨有机盐水杨酸钠(NaSal)对表面活性剂3-十六烷氧基-2-羟丙基-三甲基溴化铵(R_(16)HTAB)在溶液中胶束球棒形态转化的影响。模拟结果显示:在没有NaSal存在的条件下,体系中预组装好的棒状胶束不稳定,最终会断裂形成球形胶束。而随着NaSal的加入,预组装好的棒状胶束在模拟过程中虽然存在波动,但是在30 ns的分子动力学模拟中,棒状胶束依然稳定存在。Sal-离子增溶进胶束内部与表面活性剂分子之间的静电相互作用和氢键作用促进R_(16)HTAB由球形胶束向棒形胶束转化。(3)采用分子动力学模拟方法研究三种盐(水杨酸钠(NaSal)、1-萘酚-2-甲酸钠(1SHNC)、2-萘酚-3-甲酸钠(2SHNC)对表面活性剂3-十四烷氧基-2-羟丙基-三甲基溴化铵(R_(14)HTAB)在溶液中胶束球棒形态转化的影响。模拟结果表明:加入的三种盐离子均可以维持R_(14)HTAB棒状胶束稳定存在。利用aRDG方法研究了盐离子与表面活性剂分子之间的弱相互作用。通过观察aRDG散点图和等值面图,我们直观的观察到渗透进胶束不同位置的盐离子与表面活性剂分子之间的静电作用力、氢键、范德华力。氢键及静电作用力、范德华力的存在导致棒状胶束的剪切粘度增加从而胶束更加稳定。
[Abstract]:Adsorption, deposition and aggregation are physical phenomena in nature. The patterns formed by micro-nanoscale organic luminescence and small molecular positioning deposition have been widely used in many fields. Therefore, the construction of surface patterns has become a research hotspot. Because of their unique amphiphilic properties, surfactants can form many different shapes of aggregates in solution. This kind of compounds are widely used in production and life. The molecular simulation method is used to study these physical phenomena and to reveal the mechanism of these processes at the molecular level. The main work of this thesis is as follows: (1) equilibrium molecular dynamics and tensile molecular dynamics simulation are used to study the template induced organic light emitting small molecule (3OL). Selective deposition of anthracenyl) pyrazolium (ANPs) on self-assembled films. The mean force potential of the deposition process was calculated by using the umbrella sampling method and the weighted histogram analysis method. In the simulation, two kinds of alkane chain self-assembled film templates with different densities were constructed using silica as the base plate. The equilibrium molecular dynamics results show that the 1: ANP molecule is easily deposited in the low density liquid spreading phase, and the equilibrium molecular dynamics results show that the equilibrium molecular dynamics results show that the equilibrium molecular dynamics results show that the WANP molecule is easily deposited in the low density liquid spreading phase. The results of tensile molecular dynamics show that when ANP molecules are deposited on the surface of liquid compressed phase, there is a great resistance to enter the alkane film, so it is not easy to enter into the alkane chain monolayer film. By comparing the binding free energies between the two kinds of self-assembled films with different densities and ANP molecules, it was found that the energy barrier of the ANP molecules entering the liquid compressed phase was higher than that of the ANP molecules. And the combination of ANP molecules with liquid expansion is more stable, The molecular dynamics simulation method was used to study the effect of sodium salicylate on surfactant 3- hexadecoxy-2-hydroxypropyl-trimethylammonium bromide. The effect of RAP16 HTAB) on the morphological transformation of micellar bat in solution. The simulation results show that, in the absence of NaSal, The pre-assembled rod-like micelles in the system are unstable and eventually break into spherical micelles. With the addition of NaSal, the pre-assembled rod-like micelles fluctuate in the simulation process, but in the molecular dynamics simulation of 30 ns, Rod-like micelles remain stable. Electrostatic interaction and hydrogen bonding between sal-ion solubilized micelles and surfactant molecules promote the transformation of RSP 16 HTAB from a spherical micelle to a rod micelle.) Molecular dynamics simulation method is used to study the effect of molecular dynamics on the transformation of RW 16 HTAB from a spherical micelle to a rod micelle. The effects of three salts (sodium salicylate, sodium salicylate, 1-naphthol-2-sodium formate, sodium salicylate, 1-naphthol, 2-naphthol, 2-naphthol, sodium formate, sodium formate, 2SHNCon) on the morphological transformation of micelle rods of surfactant 3- 14 alkoxy-2-hydroxypropyl-trimethylammonium bromide in solution were studied. Three kinds of salt ions were added to maintain the stable existence of RSC-14HTAB rod-like micelles. The weak interaction between salt ions and surfactant molecules was studied by aRDG method. The aRDG scatter diagram and iso-surface diagram were observed. We can directly observe the electrostatic force, hydrogen bond, van der Waals force, hydrogen bond and electrostatic force between salt ions and surfactant molecules permeated into micelles at different positions. The existence of van der Waals force increases the shear viscosity of rod-like micelles and makes the micelles more stable.
【学位授予单位】：聊城大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O647.2

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