Bioaromatic-Associated Multifunctionality in Lignin-Containing Reversible Elastomers

The unique molecular structure of lignin, intrinsicallyrich inbioaromatic groups (phenolic hydroxyls), gives it, e.g., antioxidant,antistatic, antimicrobial, UV-blocking, hydrophobic, or even flame-retardantproperties, which are highly interesting. An attractive strategy touse lignin as a macro-monomer for the design of functional materialsthat retain certain of these lignin-specific properties is to partiallypreserve some phenolic groups during the synthesis. In this work,we explore the properties of reversible elastomers containing a ligninfraction whose phenolic groups have only been partially modified.To do so, Kraft lignin was first fractionated and partially (89%)modified with furan groups, allowing its homogeneous incorporationin Diels-Alder formulations. The effect of the residual phenolicgroups embedded in the polymer matrix was then systematically studied,focusing on the specific material properties associated with lignin.The obtained lignin-containing networks notably showed increased radicalscavenging activity (which directly resulted in improved antistaticand antioxidant properties), displayed improved UV absorbance dueto the presence of multiple lignin chromophores, and were even ableto inhibit the growth of bacteria. This article demonstrates thattailored and partially modified lignin fractions could be used asmulti-functional building blocks for the design of complex (and reversible)polymer architectures, mimicking some of the unique lignin functionalitiesfound in nature, and this without the need to add specific additives.