Bio-based nanocomposites obtained through covalent linkage between chitosan and cellulose nanocrystals

► Functionalized cellulose nanocrystals (CNCs) with ester end group were prepared. ► The functionalized CNCs reacted with the amino groups of chitosan (CH). ► Bionanocomposites based on chitosan covalently bonded to CNCs were obtained. ► Improvements in mechanical and water resistance properties were achieved. ► The approach used in this work can be extended to other natural polymers.