UC Santa Barbara

Epoxy thermoset represents one of the most versatile thermosetting materials that has been used as coatings, adhesives, electronic materials and structural composites. However, by far more than 90% of the epoxy cross−linked polymers involve the use of petroleum−based bisphenol A (BPA). Lignin is an abundant, low−cost and renewable source that can provide building blocks for epoxy thermosets. Lignin−derived monomers, oligomers and bulk lignin were modified through methods including demethylation, phenolation and condensation to make renewable BPA analogs. Glycidylation of these analogs followed by cross−linking process yielded renewable thermosets with marked thermomechanical properties that could replace or supplement the BPA−based counterparts. While most of the traditional epoxy thermosets cannot be reprocessed after cross−linking, incorporating reversible bonds into the backbone of thermosets can achieve stress relaxation and reversible depolymerization through cross−link exchange and bonds cleavage−reformation. This affords malleability, weldability and recyclability to the renewable thermosets.