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. ***
