Renewable Polymers from Waste Streams

Renewable polymers are needed to help reduce global dependence on petrochemicals. Many renewable polymers are also biodegradable, biocompatible, and beneficial for a variety of applications, such as compostable cups and cutlery, elastomeric shoe soles and car tires, sturdy machine parts and electronics casings, and compatibilizing agents. Lignin and fatty acids are two of the most abundant renewable waste streams that can contribute to the collection of renewable (biobased) polymers already available. Lignin is a byproduct from pulp and paper mill manufacturing and typically is burned for energy. Fatty acids can come from waste cooking oils and sometimes are fed to livestock or converted to biofuels. Alternatively, these renewable resources can provide lignin model compounds (LMCs) shown structurally in the figure and n-alkyl (“fatty”) alcohols of varying aliphatic chain-length and degree of saturation. We can incorporate such LMCs and fatty alcohols into materials through functionalization and subsequently polymerization. The functional handles and structural diversity in these biobased monomers provide means for adjusting properties to our needs. Thus, we are interested in de novo design of practical lignin- and fatty acid-based polymers, such as polycarbonate resins and block copolymer thermoplastic elastomers, to create next-generation plastics.

Another significant waste stream that holds promise as a source of renewable polymers is plastics waste. While mechanical methods of recycling plastics are commonly used, these methods require extensive sorting of waste streams, are limited to certain plastic chemistries, and result in recycled plastics which retain only a fraction of their value. Using an extremely diverse approach, including catalytic methods, polymer chemistry, and process engineering, a large degree of plastics waste can be converted into valuable products, including highly functional materials and commodity chemicals for industrial and consumer uses. Plastics waste can also be converted into monomer feedstocks for the renewable production of new plastics which retain high value. This project addresses longstanding questions in chemical recycling and upcycling in order to develop fundamental tools and approaches to make better use of plastics waste as a feedstock. The findings will ultimately lead to more sustainable plastics as well as overall reduction of waste.