嵌段聚醚非离子表面活性剂在油水界面吸附的动态Monte Carlo模拟

Dynamic Monte Carlo Simulation of the Adsorption of Nonionic Surfactants at the Oil-Water Interface by Using a Lattice Model

发展了一种利用MonteCarlo方法模拟两嵌段共聚物型非离子表面活性剂在油水界面吸附的动态算法,可以同时获得吸附过程的一些静态性质(如平衡后油水界面上所吸附的共聚物分子数目、界面层的厚度、对称性以及油水界面张力)和动态性质(如系统达到平衡所需时间等);在模拟过程中可以观察到共聚物分子在油水界面形成的亲油基伸展在油相、亲水基伸展在水相的定向排列的稳定的单分子界面膜;在其他条件一致的情况下,本文所描述的方法与静态算法所得到的界面上吸附的共聚物分子数基本相同,但略有差异,文中给出了合理的解释;绘制了界面吸附的共聚物分子数随模拟进程的变化图,当作用能参数不同时得到不同的吸附曲线,随着模拟的进行,高作用能系统平稳达到吸附平衡值,而低作用能系统的吸附曲线则在达到最大值后逐渐降低,最终达到平稳值,与文献报道的实验结果十分吻合,利用物理化学的基本原理对这些不同进行了解释。图7表2参14。

A cubic lattice model of amphiphile-oil-water system is developed in which oil and water molecules occupy single sites and amphiphiles, block-polyether of A_xB_y type, --chains of sites. The simulation shows rich structure details such as the formation and the change in size and amount of aggregates of amphiphile molecules, the stable monomolecular adsorbed layer of amphiphiles formed between oil and water phases with hydrophobic moieties oriented into the oil phase and hydrophilic moieties into the water phase. The amount of amphiphiles adsorbed on the interface under equal conditions obtained by the dynamic simulation procedure is basically similar to that by a static procedure with some differences, which are explained reasonably. The changes in the number of amphiphile molecules adsorbed on the interface during simulation are demostrated and appear coincident with the results published where else: the adsorption curves go through a maximum and then reach their equilibrium eventually for the systems with lower unfavorable interaction energy and reach their equilibrium simply for the systems with higher unfavorable interfaction energy. This phenomenon is explained in terms of physicochemical principles.