Engineering Lignin-derived Polymers to be Recyclable by Design.*

The environmental crisis caused by the modern accumulation of plastic waste has driven many to search for a circular lifecycle for commodity plastics. In this presentation, we report the results of a study aimed at chemically recycling lignin-derived non-diisocyanate polyurethanes and track the structural alteration that occurs to recycled precursors. Starting from a protocol developed in our lab for non-isocyanate polyurethane foams, a hydrolytic chemical recycling technique is used to revert waste polymers back to their precursors: lignin and a bio-derived curing agent. In addition, through the use of vulnerable "molecular zippers" throughout the polymer structure, native structural features of lignin can be regenerated during chemical recycling. By minimizing the structural alteration to lignin, the hydroxyl content can be maintained and utilized for a subsequent generation of polymer synthesis. A unique window is opened toward understanding how lignin can be used in the rational design of polymer structures specifically engineered to undergo chemical recycling at their end of life.