Complex Functional Materials Accessed Uniquely through Selective Covalent and Non-covalent Macromolecular Interactions
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PART 1: NON-TECHNICAL SUMMARYOrganic polymer materials, commonly thought of as plastics, are of critical importance to every aspect of human life, from the clothes that we wear to the computers that we use to the tires on which we drive to the devices through which medicines are administered. Due to the large, macromolecular size of polymers, there is great opportunity to vary the chemical composition and structure, throughout the entire molecular framework or in specific sub-regions, to achieve significant variation in the materials properties: i.e., flexible vs. rigid, conducting vs. insulating, etc. As the chemical structure of polymers becomes increasingly complex, their properties and technological applications also often increase. The expected significance of the proposed work will be in the advancement of synthetic chemistry approaches that allow for simple, scalable production of polymer materials that possess intricate complexity and exhibit unique physical and mechanical properties. A focus is on building the polymers to have a "bottle-brush-like" molecular architecture enabling them to exist as pre-fabricated super-size macromolecules that contain sub-regions designed for programmed assembly or degradation. From these macromolecules functional nanostructured objects can then be produced. Such objects may be able to be used as synthetic versions of viruses for synthetic vaccines, or as porous thin films for water purification, gas separation or other transport and separations applications. Other target structures will include nanostructures that are capable of oil spill clean-up with magnetic recovery. The fundamental knowledge generated is expected to impact chemistry, physics and engineering disciplines, and the project will also include multifaceted educational components. With the practical applicability of these new materials, including the specific target applications to be studied, industrial interest may be anticipated, which may translate to products offering additional societal benefits.PART 2: TECHNICAL SUMMARYThe activities of the proposed work will involve the development of advanced synthetic methodologies to afford nanoscopic materials having enhanced compositions, structures and functions. One objective is to increase the complexity of materials compositions, structures and properties, by first kinetically-trapping linear polymer precursors into covalent molecular brush architectures having pre-determined regiochemical distributions of functionalities. A second objective is to develop an understanding of the morphologies and properties that can be generated from the assembly of the resulting molecular brush building blocks in solution, thin films and the bulk. In addition to the roles of molecular architecture on the assembly processes and resulting properties, polypeptide segments will be incorporated as side chain grafts to provide for active secondary structural interactions, and degradable polypeptide or polyphosphoester portions will be built-in to allow for heterogeneous modulation of the density within nanoscopic domains of the overall materials. Beyond the fundamental objectives, specific targets will include discrete nanocage frameworks, modeled after the assembly of globular proteins into viral capsids, and extended thin-film or bulk porous polymer network materials, each of controlled dimensions and porosities for potential use in transport and separations applications. An additional objective is to further investigate hybrid inorganic-organic heterostructures that are designed to outperform our recently-developed magnetic shell crosslinked knedel-like (MSCK) nanoparticles in their capacity for crude oil recovery efforts. The methods that will be employed will include combinations of polymerization and chemical modification reactions to build up the structures, homogeneous or heterogeneous supramolecular assembly methods to afford complex morphologies, crosslinking of selective regions to stabilize those morphologies, and, in some cases, degradation of selective domains within the materials. Throughout the work, rigorous characterization studies will be conducted. A broad educational and outreach program is part of this project.