Microwave-assisted esterification of bleached and unbleached cellulose nanofibers

Microwave-assisted synthetic pathway was explored for the sustainable esterification of cellulose nanofibers (CNFs) using an aromatic amine compound. For this purpose, nanofibers were isolated from unbleached and bleached eucalyptus pulp through the homogenization process. The chemical composition, the structural properties, the morphology, and the thermal properties of the extracted nanofibers were investigated. para-aminobenzoic acid (PABA) was employed to esterify CNFs's aliphatic hydroxyl groups. FTIR and 13C NMR spectroscopy confirmed the success of the chemical modification. The structural characterization of the cellulose nanofibers and lignocellulose nanofibrils esterified (CNF-E and LCNF-E) confirmed the grafting of the aromatic amine counterparts onto CNFs's surface. The thermogravimetric technique assessed the thermal stability of the nanofibrils. The thermal properties were affected by the esterification resulting in a significant improvement of the char yield (CR) compared to the original CNFs (from CR≈ 10% to > 20%). Finally, this sustainable chemical pathway increases CNFs's functionality by introducing ester and aromatic amine functionalities, making LCNF-E and CNF-E sustainable platforms for further smart applications.