UC Santa Barbara

Increasing greenhouse gas emissions and petroleum depletion have motivated the development of renewable energy sources. Nonfood lignocellulosic biomass is a promising renewable source for making liquid fuels, valuable chemicals, and materials due to its high energy content. However, the efficient utilization of biomass has been significantly hindered by its recalcitrant nature. Herein, we describe the use of genetically modified high-syringol (high-S) poplar lignin to produce 4-propyl-2,6-dimethoxyphenol (DMPP). Various lignin extraction methods and catalyst preparations were studied to optimize depolymerization yields. The produced monomer, DMPP, is then upgraded to the multi-functional compound propylpyrogallol (DMPPO) by a catalytic reaction using Nb2O5 in water or hydrobromic acid (HBr). Epoxies are used in various applications due to their excellent mechanical properties, chemical resistance, and thermal stability. Up to 90% of epoxy thermosets are made from petroleum-based bisphenol A (BPA), but interest in BPA alternatives is rapidly increasing due to toxicity concerns. The resulting DMPPO can be converted to a novel tri-epoxide by epichlorohydrin. Epoxy thermoset polymers using the two different epoxide preparations are synthesized, characterized, and contrasted. The performance of renewable lignin-based DMPPO epoxy thermosets, in terms of thermal and mechanical properties, opens avenues for the direct utilization of biorefinery products in the fabrication of bio-based polymers and offers a sustainable alternative to petroleum-based polymer materials.