Structure and Chemical Interactions at Model Polymer Interfaces

9801739 Allara这个项目的目标是为有机材料界面的潜在行为提供更多的基本理解。虽然人们普遍认识到，衬底结构和化学的细节在决定界面性质方面起着关键作用，但目前主流的聚合物界面研究只占总努力的一小部分。提出的工作是为了填补这一重要的空白，通过研究链限制在明确定义的表面以受控的方式。在此基础上，提出了三个平行的子推力：1.过渡金属表面上聚亚甲基（PM）纳米团簇表面约束的形态效应；2)表面接枝链组件润湿过程中的界面重建效应；3)在受控结构表面位置和/或受次级吸附物质约束的吸附柔性链的结构和动力学。在区域1中，工作将深入探讨约束对PM在不同金属晶面上的结构和相变的影响。此外，聚合物将通过侧链的内含物和有限的延伸来改变，以制备新型的聚合物纳米复合材料。在区域2中，将进行相关的实验和理论研究，以更广泛地了解表面约束链系统中润湿诱导的重建。在区域3中，被吸附聚合物的链结构密度分布将与“调谐”的衬底固定位点模式和地形相关，主要是通过分子自组装来实现的。此外，将通过化学诱导的界面扰动研究链重组和解吸动力学，以及化学吸附的分子陷阱（“钉”）施加的链约束对解吸动力学的影响。总的来说，这些研究跨越了柔性链结构，从固体纳米晶体到无序链组装，局限于化学和地形控制的表面。预计这项工作的结果将对从聚合物粘附到微电子到生物相容性等领域产生影响。它们可以提高对复杂有机界面性质的定量模型的能力，从而提高设计材料结构的能力，这些材料的性能严重依赖于这些类型的界面的性质。＊＊＊

9801739 Allara The goal of this project is to provide an increased fundamental understanding of the underlying behavior of the interfaces of organic materials. While it is generally well appreciated that the details of substrate structure and chemistry play a critical role in determining the interface properties, the current mainstream research in polymer interfaces has placed only a small fraction of total effort here. The proposed work is intended to fill this important gap through studies of chains confined at well-defined surfaces in controlled ways. Based on new developments in the past results from the principal investigator's work, three parallel sub-thrusts are proposed: 1.) morphological effects of surface confinement of polymethylene (PM) nano-clusters on transition metal surfaces; 2.) interface reconstruction effects in wetting of surface-grafted chain assemblies; and 3.) structure and dynamics of adsorbed flexible chains constrained at controlled architecture surface sites and/or by secondary adsorbate species. In area 1 the work will probe deeply into confinement effects on structure and phase transitions of PM on varied metal crystal faces. Further, the polymer will be varied by inclusions of side chains and limited extensions will be made to prepare novel types of polymer nano- composites. In area 2 connected experimental and theoretical studies will be made to develop a broader understanding of wetting-induced reconstruction in surface-constrained chain systems. In area 3 the chain structure density distribution for adsorbed polymers will be correlated with "tuned" substrate pinning site patterns and topography, primarily made via molecular self-assembly. In addition, chain reorganization and desorption dynamics will be studied via chemically-induced interface perturbations and effects of chain confinement imposed by chemisorbed molecular traps ("staples") on desorption kinetics studied. Overall these studies span flexible chain structure s, ranging from solid nanocrystallites to disordered chain assemblies, confined at chemically and topographically controlled surfaces. %%% The results of the proposed work are expected to have impact in areas ranging from polymer adhesion to microelectronics to biocompatability. They may provide an increased ability to make quantitative models of the properties of complex organic interfaces and thereby to enhance the ability to engineer materials structures whose performance depends critically upon the nature of these types of interfaces. ***