Proximal Adsorption in Colloidal Systems

弗吉尼亚理工学院和州立大学的William a . Ducker博士的胶体系统近端吸附研究获得了化学学部物理化学项目的资助。他将在一个由硅颗粒和季铵表面活性剂组成的模型系统中测量表面活性剂的吸附，作为颗粒之间分离的函数（近端吸附）。在粒子力和稳定性的分析中，通常假设表面活性剂在粒子碰撞时不吸附或解吸。这可能导致严重的错误。他的力-距离-吸附测量结果将用于确定近端吸附对胶体力的影响。结果还将与Hall和Ash等人开发的热力学理论进行比较，并使用自洽场计算探索近端吸附背后的微观机制。他将使用相互作用驱动吸附的概念作为提高对表面活性剂和聚合物体系中胶体稳定性理解的途径。与传统的静电和统计力学计算相比，这种方法的优点是方法简单，并且力与最容易控制的实验参数直接相关：溶液中添加剂的浓度。研究生和本科生将接受表面化学理论和实验方法的培训，并将参与开发一种测量近端吸附的新仪器。我们在日常生活中遇到的许多物体实际上都是由非常细小的粒子组成的。例如，砖、纸、衣服、瓷器、土壤、大多数食物、化妆品，甚至人类都是由小颗粒组成的。这些物体的物理性质（如刚度、流动性和可加工性）取决于粒子之间的作用力。创造新产品和改进产品的部分过程是操纵颗粒之间的力以获得理想的材料性能。在实践中，这些新的性能是通过添加表面活性剂和聚合物获得的，它们吸附在颗粒的表面。我们知道这种吸附会因颗粒之间的碰撞而发生改变，但在大多数理论中没有考虑到这种影响，因此在配制产品时通常采用的推理缺少了一个关键步骤。这项研究的目的是测量、模拟和理解碰撞过程中吸附的变化。这将为预测材料的物理性质提供新的指导。

Dr. William A. Ducker of Virginia Polytechnic Institute and State University is funded for his research on proximal adsorption in colloidal systems by a grant in the Physical Chemistry program of the Chemistry Division. He will measure the adsorption of surfactants as a function of the separation between particles (the proximal adsorption) in a model system consisting of silica particles and quaternary ammonium surfactants. In the analysis of particle forces and stability, it is common to assume that surfactants do not adsorb or desorb when particles collide. This can lead to serious errors. His results of force-distance-adsorption measurements will be used to determine the effect of proximal adsorption on colloidal forces. The results will also be compared to the thermodynamic theory developed by Hall and by Ash et al., and the microscopic mechanism behind proximal adsorption will be explored using self-consistent field calculations. He will use the concept of interaction-driven adsorption as a route for improved understanding of colloidal stability in surfactant and polymer systems. The advantages of this approach over conventional electrostatic and statistical mechanical calculations are that the approach is simple, and the force is directly linked to the most easily controlled experimental parameter: the concentration of additive in solution. Graduate and undergraduate students will be trained in both theoretical and experimental approaches to surface chemistry, and will join in the development of a new apparatus for measuring proximal adsorption.Many of the objects that we encounter in everyday life actually consist of very fine particles. For example, bricks, paper, clothing, china, soil, most foods, cosmetics, and even humans are composed of small particles. The physical properties (e.g. stiffness, flow, and workability) of these objects depends on the forces between the particles. Part of the process of creating new and improved products is the manipulation of the forces between particles to obtain desirable material properties. In practice these new properties are obtained through the addition of surfactants and polymers, which adsorb to the surface of the particles. We know that this adsorption is modified by collisions between the particles, but this effect is not taken into account in most theories, and therefore the reasoning commonly employed in formulating products is missing a key step. The aim of this research is to measure, model, and understand the change in adsorption during a collision. This should provide new guidelines for predicting the physical properties of materials.