9807696 Blum This award will enable study ofthe segmental motion of polymers at interfaces, particularly those attached to solid surfaces. The interfaces in multiphase materials, such as those in composites, coatings, nano- and electronic materials play an important role in determining the physical properties of those systems. Since the interfaces themselves are quite thin, and as the size of structures is reduced, the effects of the interfaces become even more difficult to properly characterize with macroscopic physical testing. Spectroscopic techniques, especially deuterium nuclear magnetic resonance (NMR), will be used to study the microscopic properties of the polymers at interfaces with solid substrates. The use of deuterium labelling is important because specific deuteration is not a significant perturbation of the segmental motion of the polymer-the deuterons act as reporter groups based on their position which is synthetically controlled. The focus will be on the dynamics (i.e. molecular motion) of polymer segments. Segmental motion has not been studied as much as the structures of the interfacial species; however, both determine the ultimate properties of the systems used. This work builds on work previously funded by NSF where deuterium NMR has been shown to be a powerful tool for probing the motions of adsorbed polymers. For homopolymers adsorbed on solid surfaces, a motional gradient in a single-molecule thick film has been identified. However, the characterization of this gradient/layer was incomplete. It is proposed that experiments on composite materials, where the labelled polymer is adsorbed on the solid substrate and an unlabelled polymer is absorbed over it, be performed. These will identify how the presence of an overlayer affects the interfacial layer. With the sensitivity of the NMR instrumentation available, it is also proposed that two- dimensional exchange NMR experiments be performed in order to quantitatively estimate the rates and amounts of different motional species present in the interfacial polymers. %%% The result of the successful completion of this work will be that knowledge of the structure and dynamics of interfacial materials will help researchers to design interfacial systems with enhanced properties for advanced applications such as advanced composite structures, electronic devices, particle stabilization, and adhesive properties. ***
