Wetting Properties of Surfactant Systems

本研究的目的是从理论上和实验上研究表面活性剂体系的润湿行为，重点是微乳液。将发展一种新的润湿转变热力学理论，其中将考虑到在这些系统中很重要的重力效应。与表面活性剂结构有关的润湿转变发生的条件也将与本研究一起进行。实验方法包括新的滴定量热法，动态接触角分析和增强的视频显微镜。一个基于分子热力学的新理论模型将被开发出来，它只依赖于容易测量的参数，允许直接比较预测和实验结果。本文的研究具有重要的理论意义和现实意义。这将有助于我们对表面活性剂体系中界面现象的基本理解，以及表面活性剂体系的性质发挥重要作用的众多应用，如提高采收率，洗涤剂，液体印刷，微电子，磁记录介质，以及新的分离过程。最近已经观察到，当人们离开微乳液系统的临界点时，微乳液相和过量相之间会发生润湿转变。这种现象只发生在某些表面活性剂上。提出的工作将研究表面活性剂结构在润湿转变中的作用。它将侧重于微乳液形成的理论模型的发展，该模型将以一种新的方式处理相间区域在微乳液形成中的作用。具体来说，界面的结构将与相之间的界面张力有关。由于模型将只包含可测量的热力学参数，模型预测湿润转变的能力将严格检验模型。本文的研究具有重要的理论意义和现实意义。这将有助于我们对表面活性剂系统中界面现象的基本理解，以及表面活性剂系统的界面特性在许多工程应用中起着重要作用，如提高采收率，洗涤剂，液体印刷，微电子，磁记录介质和新型分离工艺。

The objective of this proposed research is to study both theoretically and experimentally the wetting behavior of surfactant systems, with emphasis on microemulsions. A new thermodynamic theory of wetting transitions will be developed in which the effects of gravity, which are important in these systems, will be taken into account. Conditions under which wetting transitions occur, as related to the structure of the surfactant, will also be undertaken in conjunction with this study. Experimental methods to be used include novel titration calorimetry, dynamic contact angle analysis, and enhanced videomicroscopy. A new theoretical model, based on molecular thermodynamics, will be developed, which relies only on readily measurable parameters, allowing a direct comparison of predictions and experimental results. The proposed research is of both fundamental and practical significance. It will be beneficial to our fundamental understanding of interfacial phenomena in surfactant systems as well as the numerous applications in which the properties of surfactant systems play an important role, such as enhanced oil recovery, detergency, liquid printing, microelectronics, magnetic recording media, and novel separations processes. It has recently been observed that, as one moves away from a critical point in a microemulsion system, a wetting transition can occur between the microemulsion phase and the excess phases. This phenomenon occurs only for some surfactants. The proposed work will investigate the role of surfactant structure in the wetting transition. It will focus on the development of a theoretical model of microemulsion formation which will deal in a novel manner with the role of the interphase region in the formation of microemulsions. Specifically, the structure of the interphase will be related to the interfacial tension between the phases. As the model will contain only measurable thermodynamic parameters, the ability of the model to predict a wetting transition will rigorously test the model. The proposed research is of both fundamental and practical significance. It will be beneficial to our fundamental understanding of interfacial phenomena in surfactant systems as well as to the numerous engineering applications in which the interfacial properties of surfactant systems play an important role, such as enhanced oil recovery, detergency, liquid printing, microelectronics, magnetic recording media, and novel separations processes.