As the second most abundant natural polymer after cellulose, lignin provides an ideal platform for the development of novel polymeric and composite materials. Lignin is isolated from plant materials through the industrial processing of lignocellulosic biomass during the production of paper or ethanol. While the polysaccharide components of biomass are well-utilized, lignin is considered a low value byproduct and has little commercial use. In 2011, the worldwide pulp and paper industry produced 50 million tons of lignin but only 2% was used commercially and the rest was burned as a low value fuel. An opportunity therefore exists to utilize lignin as widely available low value carbon source to produce new commodity and high performance polymeric materials. Monolignols (the monomers that form lignin) and their derivatives (including hydroxycinnamates, a biosynthetic precursor to monolignols) are particularly attractive because they possess an aromatic group, which is quite uncommon in other natural polymers. Introduction of aromatic units into polymers typically improves their thermal and mechanical properties (compared to aliphatic polymers), We developed a series of monomers based on hydroxycinnamates, and incorporated them into polymers via condensation polymerization. Approximately 40 different polymeric structures were synthesized, with a broad range of molecular weights and molecular weight distributions. The resultant polymers exhibit good thermal stability and were typically amorphous (although a few samples exhibited a melting point). However, the polymers generally exhibited very limited solubility in common organic solvents (excluding DMF). These results suggest that hydroxycinnamate-based copolymers may find use in applications where thermal stability and solvent resistance are desired. Furthermore, these results indicate that lignocellulose may be useful as a new feedstock for commodity polymeric materials.

Biomass-derived polymers incorporating hydroxycinnamates

253rd National Meeting (2017)

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