Controlled Radical Polymerization of Crude Lignin Bio-oil Containing Multihydroxyl Molecules for Methacrylate Polymers and the Potential Applications

In this work, methacrylate polymers with different thermal and viscoelastic properties were synthesized from red oak lignin bio-oil. The bio-oil, also called pyrolytic lignin (PL), consisted of various phenolic monomers and oligomers with average hydroxyl content of 3.04 mol/mol. The PL was first esterified with different amounts of methacryloyl chloride and acetyl chloride to form PL methacrylates and then subjected to reversible addition–fragmentation chain transfer polymerization. Polymerization of fully methacrylated PL caused gelation to yield a cross-linked polymer. On the other hand, gel-point suppression occurred in the polymerization of partially methacrylated PL to yield a thermoplastic polymer with glass transition temperature (Tg) of 161 °C and thermal decomposition temperature (Td) of 241 °C. In comparison, the functionalization of PL by partial methacrylation and subsequent acetylation resulted in a polymer with Tg of 130 °C and Td of 250 °C. Unlike other biobased methacrylate polymers that ...