Lignin is an important potential source of synthetic materials because of its abundance in nature and low production cost. However, the current use of lignin as a raw material is very limited and focused only on cheap and poorly-defined nonfunctional materials. The present research reports natural lignin’s a new chemical modification method which is low energy and environmentally friendly technology. The chemical modification is a visible light induced thiol-ene photoredox reaction. The thiol−ene reaction between lignin−alkene and 1-decanethiol revealed that Ru(bpy)3Cl2 was the most efficient, resulting in conversions of 97% with 2.5 mol % catalyst loading. The Ru(bpy)3Cl2 was further investigated with diverse thiol compounds including poly(ethylene glycol). In addition to the new lignin modification chemistry, a self-healing property lignin-based polymer was synthesized by copper catalyzed click reaction. The new functional lignin-based polymer is lignin-graft-poly(5-acetylaminopentyl acrylate) (lignin-graft-PAA), which has acetylamino groups on their pendants to generate strong hydrogen-bonding for self-healing properties. In the synthesized lignin-graft-PAA, 5−20 wt % lignin demonstrated the most optimal rubber-like, flexible property. The self-healing property presented recovering up to 93% of its original maximum stress before severance.

New chemistry to modify natural lignin: synthesis of lignin-based functional polymers

2019 Spring National Meeting

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