In this project funded by the Macromolecular, Supramolecular and Nanochemistry Program of the Chemistry Division, Karen L. Wooley of Texas A&M University will design synthetic strategies for the development of polymer materials that originate from renewable resources, exhibit novel combinations of strength, toughness, and hydrolytic degradability, and undergo breakdown to biologically-beneficial or benign by-products. This project combines polyhydroxy natural products as the monomeric building blocks, and carbonates, found in common engineering materials, as the linkages. Hydrolytic degradation will produce the polyhydroxy compound plus carbon dioxide. Two classes of natural monomers, D-glucose and quinic acid, will be evaluated for the construction of polycarbonates, each of which will hydrolyze to carbon dioxide plus the saccharide or quinic acid, respectively. The physical, mechanical and stability properties will be tuned by the chemical compositions and structures, controlled by the advancement of synthetic methodologies by which to prepare such materials. The broader impacts involve (1) diverse and extensive education, training and recruiting of the next generation of chemists, who are capable in chemistry and engineering, (2) advances to synthetic polymer chemistry, and (3) the creation of novel materials that have the potential to positively impact society. Students/postdoctoral associates will be trained in synthetic organic and polymer chemistries of challenging polyhydroxy and carbohydrate-based systems, they will gain expertise in rigorous physicochemical and mechanical characterization, they will be exposed to engineering concepts, and they will gain an appreciation for the creation of materials for important environmental, biomedical and other applications.
This work will produce polymer materials for use as engineering plastics that originate from natural sources, thereby reducing dependence on petrochemicals, and that later degrade into natural compounds, to promote biological and environmental clearance. These materials are designed with aspects of engineering-type construction materials from Nature (e.g. cellulose, chitin, etc.) that are degradable, resorbable and recyclable. Ultimately, these polymers could have the potential to replace common plastics and to be developed for high-end medical and orthopedic device applications.
The intellectual merit of the proposed work included the design of synthetic strategies for the development of polymer materials that originate from renewable resources, exhibit novel combinations of strength, toughness, and hydrolytic degradability, and undergo breakdown to biologically-beneficial or benign by-products. Although Nature has several examples of engineering-type construction materials (e.g. cellulose, chitin, etc.) that are degradable, resorbable and recyclable, most synthetic materials are designed to be derived from renewable resources and degradable or from petrochemicals and an engineering material. The fundamental work that was supported by this NSF grant allowed for the development of synthetic approaches to incorporate polyhydroxyl natural products as monomers in degradable polycarbonate materials. Polycarbonates of glucose, quinic acid, ferulic acid, tyrosine and quercetin were prepared and characterized. The development of synthetic methods that allow for the use of natural products to generate polymers that exhibit interesting physical and mechanical properties is an important step, and a finding of inherent fluorescence for some of the polymers point to new directions in sensing applications as well. The results were disseminated in five peer-reviewed publications, with additional manuscripts submitted for publication, and tens of presentations given at meetings and institutions across the U.S. A PCT patent application was filed in 2011 on this general approach to novel degradable polymers, which are derived from renewable resources, are designed to possess important physical and mechanical properties to serve as engineering materials, and are designed to undergo hydrolytic degradation to regenerate the natural product-based polyhydroxyl monomers. We continue to develop these materials as well-defined linear polymers and as crosslinked networks, making significant fundamental advances in the synthetic approaches and in the types of materials and their properties. It is expected that the materials developed under this project will ultimately be utilized as unique tissue engineering scaffolds, suture materials, bone repair devices, etc. Moreover, with our advances in polycarbonates derived from polyphenolic natural products, it is expected that they will displace bisphenol A polycarbonates, having enormous impact as engineering polymers with environmental and societal benefits. Additional broader impact outcomes included (1) diverse and extensive education, training and recruiting of the next generation of chemists, who are capable in chemistry and engineering, (2) advances to synthetic polymer chemistry, and (3) the creation of novel materials that have the potential to positively impact society.