Research Initiation Awards: Characterization of Interdiffusion Between Layers of Langmuir-Blodgett Multilayers

该计划的目标是定量描述Langmuir-Blodgett(LB)多层膜各层之间的互扩散程度，以及了解互扩散机制和识别重要参数。这项研究将集中在一个包含两种特性良好的材料-花生四酸镉(CDA)和取代聚谷氨酸(PG)-的模型体系上。当用作光学介质时，聚谷氨酸材料具有表现出的低模式损耗，并且该系统被选择来暗示潜在的有机光学器件的某些特性。由PG双层势垒隔开的CDA层之间的互扩散将使用中子反射仪(NR)和X射线反射仪(XR)进行补充。扩散前后的界面轮廓将通过将实验反射率与使用已建立的矩阵形式计算的模拟曲线相一致来推断。通过组合两个互补的实验探头、不同的氢气对比以及使用具有良好特性的系统组件，可以最大限度地减少解释中的潜在歧义。预期的结果将极大地增加现有关于二维有序层之间相互扩散的稀少数据。对互扩散机理和控制参数的新认识将潜在地影响分子尺度有机器件的设计和模型生物膜中传输的研究。具体地说，如果一种新型的类液晶聚合物起到了有效的扩散屏障的作用，它将被证明。

The objective of this program is a quantitative characterization of the degree of interdiffusion between layers of a Langmuir-Blodgett (LB) multilayer as well as an understanding of the interdiffusion mechanism and identification of important parameters. The study will focus on a model system containing two well characterized materials, cadmium arachidate (CdA) and a substituted polyglutamate (PG). The polyglutamate material has a demonstrated low mode loss when used as an optical medium, and the system is chosen to suggest certain characteristics of a potential organic optical device. Interdiffusion between CdA layers separated by a PG bilayer barrier will be followed using neutron reflectometry (NR) complemented with x-ray reflectometry (XR). Interface profiles before and after diffusion will be inferred by reconciling experimental reflectivities with simulated curves calculated using an established matrix formalism. Potential ambiguities in interpretation will be minimized by the combination of two complementary experimental probes, variation of contrast with deuteration, and the use of system components which are well characterized. The expected results will add greatly to the meager existing data on interdiffusion between two-dimensional ordered layers. New insight into the mechanism and controlling parameters of interdiffusion will potentially impact the design of molecular scale organic devices and the study of transport in model biological membranes. Specifically it will be shown if a novel liquid-crystalline-like polymer acts as an effective diffusion barrier.