Functionalization of chitosan with lignin to produce active materials by waste valorization

The valorization of lignin to produce functionalized materials is challenging. A grafting reaction based on the reactivity between chitosan amino groups and lignin hydroxyl groups was performed, in an environmentally friendly solvent to produce thin films that can be used as active packaging or coating materials. A systematic comprehensive study was performed, that focused first on the grafting of the three phenolic acids composing lignin (coumaric, ferulic, and sinapic acids), and then of the lignin polymer itself onto chitosan. The anti-oxidant activity of lignin monomers was preserved after grafting onto chitosan with significant differences regarding their initial radical scavenging activity: sinapic acid > ferulic acid > coumaric acid. The lignin polymer can also be grafted onto chitosan, which results in an intermediate anti-oxidant activity of the film. Therefore, this work opens a new route for the valorization of lignin, with the possibility of tuning the anti-oxidant activity of the final material based on the appropriate selection of the initial sustainable resource. Active films are produced by a grafting reaction based on the reactivity between chitosan amino groups and lignin hydroxyl groups. This opens a new route for the valorization of lignin, with the possibility of tuning the anti-oxidant activity.