Natural cuticle-inspired chitin/silk fibroin/cellulose nanocrystal biocomposite films: fabrication and characterization

Abstract

Abstract This study aims at developing a green sustainable bio-inspired composite film by combining the flexible chitin/silk fibroin matrix (CT/SF) and the rigid cellulose nanocrystals (CNC) with the multi-layer chiral nematic structure. The effects of CNC concentration on the chemical bonding, optical- and micro-morphology, thermal stability and mechanical properies of chitin/silk fibroin/cellulose nanocrystal (CT/SF/CNC) were comprehensively investigated. The results indicate that a critical concentration for CNC at 2 wt% can display the obvious iridescent color domains of biocomposite films with potential optical functional property. There is a color shift from blue to yellow-red corresponding to the higher concentrations at 3.5 and 5.0 wt%, respectively. The concentration of CNC also affects the transition of conformation of SF from the random to the β-turn as well as the bonding ability between SF and CT. The CT/SF/CNC-3.5 wt% with the excellent optical and mechanical properties as well as the improved thermal stability breaks the conventional conflict between increased strength and compromised ductility. Its tensile strength and elongation at break effectively elevate by 282% and 42%, respectively.