Thin Liquid Films - Structure and Stability

CTS9423584，D.T.伊利诺伊理工学院CTS9423584本研究的目的是从实验和理论上检验由布朗粒子的表面活性剂胶束稳定的流体表面亚微米薄膜中的多层微结构或分层现象，并进一步探索其作为探针在研究胶体分散体系中诱导长程结构力的有序性方面的应用。这项持续研究的一个独特之处在于，使用其最新的仪器表面力天平对具有流体界面的弯曲薄膜进行了研究，以研究多层微结构对薄膜厚度稳定性的影响。表面力天平将与差示干涉显微镜一起用于研究对称的泡沫和乳胶膜以及不对称膜，例如接近的小油滴与空气-水表面或水滴与空气-油表面之间的膜。使用阿贡国家实验室先进的光子源的同步辐射X射线衍射将被用来直接观察具有流体表面的薄液体薄膜的本征层内结构。用微分和普通的显微干涉方法进行实验，以获得薄膜弯月面的局部平均曲率和薄膜/弯月面接触角，从而得到薄膜的过剩能量和由于薄膜内部胶束结构的存在而产生的分离压力。利用激光共聚焦扫描荧光显微镜和低角度透射光衍射技术研究了薄液膜与弯月面之间的胶束/颗粒结构。这些实验将与我们的蒙特卡罗和分子动力学模拟进行比较。将评估影响膜结构和稳定性的重要技术因素，如有效胶束/颗粒体积分数、膜尺寸和膜厚度、颗粒尺寸、形状和聚分散性。要研究的体系将包括球形和非球形胶束、混合胶束(如阴离子和非离子胶束溶液的混合物)、蛋白质和带电差异的胶体粒子，如乳胶和二氧化硅，以及亲水胶体，如胶和淀粉。这项关于薄膜液膜现象的研究旨在了解表面诱导的结构/耗尽力在稳定或不稳定泡沫、乳液和乳胶分散体中的作用。

ABSTRACT CTS9423584 Wasan, D.T. Illinois Institute of Technology The objective of this research is to examine, both experimentally and theoretically, the phenomenon of multilayered microstructuring or stratification in sub-micron thin liquid films with fluid surfaces stabilized by surfactant micelles of Brownian particles; further to explore its use as a probe for investigating order inducing long-range structural forces in colloidal dispersions. A unique feature of this continuing study lies in the use of its newly instrumented surface force balance for curved films with fluid interfaces for investigating the influence of multilayered microstructuring on film thickness stability. Surface force balance will be used in conjunction with differential interference microscopy to study symmetric foam and emulsion films as well as asymmetric films such as those between approaching small oil droplets and an air-water surface or water droplets and an air-oil surface. X-ray diffraction using synchrotron radiation from the advanced Photon Source at Argonne National Laboratory will be used to directly observe the intrinsic, in-layer structure within thin liquid films with fluid surfaces. Experiments using differential and common microinterferometric methods will be performed to obtain the local mean curvature of the film meniscus and the film/meniscus contact angles and, thereby, the film excess energy and the disjoining pressure attributable to the presence of micellar structure inside the film. It is proposed to investigate the micellar/particle structure in the region between the thin liquid film and the meniscus, i.e., inside the wedged film by using Confocal Scanning Laser Fluorescence Microscopy as well as low-angle, transmitted light diffraction technique. The experiments will be compared with our Monte Carlo and Molecular Dynamics simulations. Important technological factors affecting the film structure and stability, such as effective micelle/particle volume fraction, film size and i ts thickness, particle size, shape and polydiserpisity, will be evaluated. Systems to be investigated will include both spherical and non-spherical micelles, mixed micelles (such as mixtures of anionic and nonionic micellar solution), proteins, and differentially charged colloidal particles such as latexes and silica, and hydrocolloids such as gums and starches. This study on thin liquid film phenomena is aimed at understanding the role of surface-induced structural/depletion forces in stabilizing or destabilizing foams, emulsions, and collodical dispersions.