Intellectual Merit: This university (Southern Mississippi) and industry (Hybrid Plastics Inc.) cooperative research proposal will investigate the effects of incorporating into waterborne polyurethanes (PU) functional nanoscale fillers (such as reactive polyhedral oligomeric silsesquioxanes (POSS) consisting of an eight-corner, -(SiO1.5)n-based cage bearing one or more functional groups) to yield new hybrid PU/POSS films with potential solid-state properties such as enhanced bioactivity & non-thrombogenicity, thermal stability, flame resistance, excellent environmental durability in atomic oxygen, and improvement in mechanical properties. The ultimate goal of the project is to develop new knowledge on how variations in the hybrid PU/POSS composition, temperature and flow conditions can be used to tune the self-assembled morphologies of the final products (such as stents, thin films, and high-performance protective coatings) to prescribed macromolecular structure and properties; and invent new applications. In addition, the research will investigate the molecular origin of the structure, rheological properties and thermomechanical behavior of well-characterized hybrid PU/POSS polymers. Such studies on solvent-cast PU/POSS thin films as functions of different composition, chain extension/configuration, and particle size will enable one to shed light on how controlled changes in the strength and range of particle interactions alter the phase behavior, morphology and rheology of the hybrid PU/POSS system, and consequently on the mechanical, thermal and dynamical behavior of the solid PU/POSS hybrid films.
The results obtained from these studies will provide a quantitative basis for testing existing theories on self-assembly of polymer morphologies and fractal gels reported in the literature on relatively simpler polymer systems in the microscopic length scales, and may reduce or eliminate costly "trial and error" practices common in the literature and industry, allowing a route to rational design of synthesis and processing conditions at the nanometer length scale for this class of materials. In addition, the project is expected to discover novel phenomena that will provide new scientific challenges for theorists and computational materials scientists, making an important contribution to chemical engineering, materials science & engineering, and rheology. Further, the insights obtained from the advanced NMR and from other characterization methods will form a fundamental basis for the improved design of nanostructured materials with enhanced benefits and for controlling the phase structure dynamics of the materials in a feedback mechanism that will account for the materials improvements as a function of the reactive processing conditions. The targeted PU/POSS hybrids (which are different from conventional polymers, polymer nanocomposites and microcomposites) would be useful because many of the intrinsic properties of the PU and POSS are complementary, and they hold great promise for future high-end uses such as in biomedical devices, especially at cardiovascular interfaces, where other polymers are not useable. The academic liaison with industry will provide critical guidance and clear focus on relevance of the project.
Broader impacts: The results of this work will play an important role in the Nation?s current interest in developing micro- and nano length scale material and processing technologies. The materials are expected to possess desirable morphologies by self-assembly as well as many desirable properties such as good chemical resistance, water resistance, solvent resistance, toughness, abrasion resistance, durability, favorable melt/solution rheology, and good thromboresistant properties, making them widely applicable. The project will provide training for 1 PhD student, as well as provide research opportunities for undergraduate students. In addition, the research may lead to development of advanced characterization methods that can serve as broad-based tools for fundamental analysis of polymeric films and dispersions. By combining university and industrial efforts, this proposal will avoid the disappointing progress seen in prior attempts to follow one approach while neglecting others. The University of Southern Mississippi has a sizable minority student population who could benefit from training in the broad area of polymer reaction engineering.
