Fabrication, Nanomechanical Properties, and Surface Functionality of Polymer Nanocomposites

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Advances in nanomanufacturing greatly depend on basic understanding of how to control building blocks of materials. Polymers have attracted significant attention in recent years, largely due to the rapid emergence of biotechnology and microelectronics. However, basic knowledge of the surface properties of polymers, often affecting component functionality more profoundly than bulk properties, and in-depth understanding of underlying deformation mechanisms at the nanoscale is very sparse. The central theme of this research is to bridge this gap by performing nanomechanical testing and surface chemical analysis on micrometer-thick polymer specimens manufactured by spin casting. The model polymers selected for study are polyurethane elastomers, comprising two insoluble monomers of relatively low and high glass transition temperatures, referred to as soft and hard segments, respectively. The principal objective is to examine the surface nanomechanical properties and adhesion (friction) characteristics in terms of polymer composition, contact load, elongation strain, and time under fixed elongation. The surface texture and material properties of pre-strained nanocomposite specimens will by studied by atomic force and surface force microscopy, while the surface chemical behavior at different strain levels and time under constant elongation will be analyzed by sum frequency generation vibrational spectroscopy. The information derived from this research will enhable enginnering of chemomechanical behavior of polymer nanocomposites, with direct implications to the manufacturing of nanodevices exhibiting tailor-made properties and multi-arrays/bio-implants possessing either hydrophilic or hydrophobic chemical behaviors, depending on the surface composition and applied strain. In addition, this project will provide the opportunity to two graduate students to become invovled with interdisciplinary research dealing with polymer mechanical property evaluation and chemical analysis at submicron scales using surface-specific state-of-the-art microsocpy and spectroscopy techniques. Such combination of surface-sensitive instrumentation is one of the strengths of this proposal. Results from this research will be incroporated in the content of a graduate course taught annualy by the PI, which currently addreses only bulk polymer behavior. This initiative will also enable the development of collaborations with industry involved with polymer biomaterials research and development, thereby increasing the application range of the obtained basic knowledge regarding the evolution of surface mechanical properties and chemical characteristics of strecthed polymer nanocomposites.