Molecular Design of Lignin-Derived Side-Chain Phenolic Polymers toward Functional Radical Scavenging Materials with Antioxidant and Antistatic Properties

This article reports a new family of functional side-chainphenolicpolymers derived from lignin monomers, displaying a combination ofproperties that are usually mutually exclusive within a single material.This includes a well-defined molecular structure, transparency, antioxidantactivity, and antistatic properties. Our design strategy is basedon the lignin-derived bioaromatic monomer dihydroconiferyl alcohol(DCA), a promising and yet largely unexplored asymmetrical diol bearingone aliphatic and one phenolic hydroxyl group. A lipase-catalyzed(meth)acrylation protocol was developed to selectively functionalizethe aliphatic hydroxy group of DCA while preserving its phenolic groupresponsible for its radical scavenging properties. The resulting mono-(meth)acrylatedmonomers were then directly copolymerized using reversible addition-fragmentationchain-transfer (RAFT) polymerization without any protection of thephenolic side chains. Kinetics studies revealed that, under selectconditions, these unprotected phenolic groups surprisingly did notinhibit the radical polymerization and lead to polymers with definedmolar masses, low dispersities, and block copolymers. Finally, applicationsof these new radical scavenging polymers were demonstrated using anantioxidant assay and antistatic experiments. This research opensthe door to the direct incorporation of natural antioxidants withinthe synthetic polymer backbones, increasing the biobased content andlimiting the leaching of potentially harmful additives.