Adsorption of Surfactant Mixtures at Solid-Liquid Interfaces: A Study of Interactions and Dynamics Using Spectroscopic, Electrokinetic, and Calorimetric Techniques

9622781 Somasundaran表面活性剂在许多商业工艺中都有使用，但制备异构纯表面活性剂所涉及的固有困难和过高的成本使得使用表面活性剂混合物成为必要。此外，表面活性剂混合物的性能远远优于单独的成分，这导致在许多产品中故意添加表面活性剂混合物，如洗涤剂和化妆品。在大多数应用中，表面活性剂的有效性取决于吸附（或不吸附）以及被吸附层的微观结构。在了解表面活性剂的吸附机制方面已经做了很多工作，但对表面活性剂混合物的研究却很少。成功设计试剂组合的关键取决于对溶液和固液界面形成的表面活性剂结构的微观和纳米结构特征的理解，以及基于单个组分性质的预测模型的发展。本研究的目标是通过多管齐下的方法，将传统的吸附、动力学、润湿性和微量热法与现代光谱技术如荧光、电子自旋共振（ESR）、光漂白后荧光恢复（FRAP）和二次谐波产生（SHG）相结合，研究不同特性的表面活性剂与混合吸附层的微纳米结构之间的相互作用。荧光光谱和ESR光谱将用于测定吸附层的微极性、微粘度和聚集数；FRAP探测所涉及的动态；在界面处探测分子的相对和绝对取向。pH、表面活性剂结构、盐度、温度和扰动对这些参数的影响将被确定，以帮助阐明吸附机理和相关动力学。除了线性烷基芳基磺酸盐和二甲苯磺酸盐等表面活性剂外，新型糖基环境友好型表面活性剂将是研究的重点。预计，已经成功用于单一表面活性剂的多管齐下的实验和理论方法将有助于开发表面活性剂混合物在固体上吸附的预测模型。* * *

9622781 Somasundaran Surfactants find use in several commercial processes but the inherent difficulty and excessive costs involved in preparing isomerically pure surfactants has necessitated the utilization of surfactant mixtures. Moreover, the performance of mixtures of surfactants is far superior to that of the individual components which has resulted in the deliberate addition of surfactant mixtures in many products such as detergents and cosmetics. The effectiveness of the surfactant in a majority of the application s depends upon the adsorption (or lack of it) as well as the microstructure of the adsorbed layers. Much work has been done to understand the mechanisms involved in determining adsorption of surfactants but very little of it has been with mixtures of surfactants. The key to the successful design of reagent combinations depends upon the understanding of the micro and nanostructural features of surfactant structures formed in solution and at solid-liquid interfaces coupled with the development of predictive models based upon the properties of individual components. It is the goal of the proposed research to investigate the interactions between surfactants of different characteristics and the micro and nanostructures of the mixed adsorbed layers using a multi-pronged approach combining classical tools of adsorption, electrokinetics, wettability and microcalorimetry with modern spectroscopic techniques such fluorescence, electron spin resonance (ESR), fluorescence recovery after photobleaching (FRAP), and second harmonic generation (SHG). Fluorescence and ESR spectroscopy will be used to determine the micropolarity, the microviscosity and aggregation numbers of the adsorbed layers; FRAP to probe the dynamics involved; SHG to probe the relative and absolute orientation of the molecules at the interface. Effects of pH, surfactant structure, salinity, temperature and perturbations in these parameters will be determined to assist in elucidating the adsorption mechanisms and associated dynamics. In addition to the surfactants such as linear alkyl aryl and xylene sulfonates, novel sugar based environmentally friendly surfactants will be a focus of the study. It is expected that the multi-pronged experimental and theoretical approach that has been successfully used for single surfactants will help in developing predictive useful models for adsorption of surfactant mixtures on solids. ***