Fluctuations and Structure at Liquid-Liquid Interfaces

同步加速器x射线表面散射和布鲁斯特角度显微镜将用于研究和教育项目，以调查液-液界面的波动和结构。学生将被训练使用尖端的同步加速器技术来研究界面现象。本研究解决了对液-液界面的分子排序和结构知之甚少的领域。这一跨学科领域对于理解凝聚态系统中的不均匀性和软界面中的分子组织具有重要的意义。其结果将与一系列化学和生物系统相关。研究领域包括：(1)水-油界面表面活性剂单层的分子有序和相变；(2)检验毛细管波和本征结构在确定水与烷烃界面宽度中的作用的最新假设；(3)通过研究湿膜中短距离相互作用的波动界面来确定界面哈密顿量；(4)开发一种新的模型系统，适合于更大的生物分子在脂质膜上吸附的结构研究。表面活性剂分子优先吸附在两种液体（如油和水）的界面上。表面活性剂起着桥梁的作用，将两种材料连接在一起，否则就无法混合。这些表面活性剂在许多国内产品中发挥着重要作用，如洗发水、油漆和塑料。更重要的是，表面活性剂构成了支持地球上生命形成的生物细胞膜的基础。从凝聚态物理的角度来看，了解大量分子如何在界面上排列是很重要的，因为这些界面的组成决定了材料的许多重要性质。化学家和生物学家也对分子自我排列和通过液体界面运输的方式感兴趣。这是很重要的，例如，在分离有毒和无毒化学物质和控制哪些生物分子可以进入细胞的不同部分或细胞之间的液体区域。由于这些系统的重要性，人们对它们进行了多年的研究。然而，在分子长度尺度上对其结构的理解尚缺乏。在过去的三年里，美国国家科学基金会的支持使得强大的x射线散射技术得以发展，这种技术可以直接探测液-液界面上的分子组织。本基金支持培训学生进一步发展这些技术，并将其应用于物理、化学和生物物理领域。

Synchrotron x-ray surface scattering and Brewster angle microscopy will be used in a program of research and education to investigate fluctuations and structure at the liquid-liquid interface. Students will be trained to use cutting-edge synchrotron techniques to study interfacial phenomena. This research addresses the poorly understood area of molecular ordering and structure at liquid-liquid interfaces. This interdisciplinary area has important consequences for understanding inhomogenieties in condensed matter systems, and molecular organization at soft interfaces. The results will be relevant to a range of chemical and biological systems. The areas of study are: (1) Molecular ordering and phase transitions in surfactant monolayers at the water-oil interface, (2) Test of a recent hypothesis about the role of capillary waves and intrinsic structure in determining the interfacial width between water and alkanes, (3) Determination of the interfacial Hamiltonian through the study of fluctuating interfaces interacting over short distances in thin wetting films; and (4) Development of a new model system suited for structural studies of the adsorption of larger biomolecules to lipid membranes.Surfactant molecules preferentially adsorb to the interface between two liquids, such as oil and water. The surfactants act as a bridge that connects two types of materials that would, otherwise, not mix. These surfactants play an important role in many domestic products, such as shampoos, paints, and plastics. More importantly, surfactants form the basis for biological cell membranes that support the formation of life on earth. From the point of view of condensed matter physics, it is important to understand how large numbers of molecules arrange themselves at interfaces because the makeup of these interfaces determine many important properties of materials. Chemists and biologists are also interested in the way molecules arrange themselves and transport through liquid interfaces. This is important, for example, in the separation of toxic from non-toxic chemicals and in controlling which biological molecules can enter different parts of cells or the liquid region between cells. Due to the importance of these systems they have been studied for many years. However, an understanding of the structure on the molecular length scale is lacking. During the past three years, NSF support has enabled the development of powerful x-ray scattering techniques that directly probe the organization of molecules at the liquid-liquid interface. The present grant supports the training of students in the further development and application of these techniques to areas of physical, chemical, and biophysical interest.