Synthesis and Investigation of Nitrile-Containing Polymers Inspired by Lignin

Abstract: The lignin-inspired derivatives coniferyl aldehyde and sinapyl aldehyde were used to prepare nitrile-containing methacrylate monomers with the aim to synthesize bio-based polymers exhibiting high glass transition temperatures (Tgs). The aldehydes were initially transformed to the corresponding nitriles and then underwent methacrylation before being polymerised by free-radical polymerisation. The homopolymers displayed very low solubility in various solvents and did not exhibit any Tgs below the decomposition temperatures, indicating that the synthesized polymers were cross-linked. Copolymers with styrene were also prepared with different compositions of the nitrilecontaining methacrylate monomers. All the synthesized copolymers displayed very low solubility, similar to the homopolymers. Copolymers prepared with ≥ 25 mol% of the nitrile monomers did not exhibit any Tg, likely due to a significant degree of cross-linking. As the nitrile monomer content in the feed decreased to ≤ 5 mol%, the polymers exhibited Tgs ranging from 126 – 146 °C. This is attributed to a decrease in the degree of cross-linking in combination with reduced intermolecular interactions due to lower amounts of the highly polar nitrile group.