Green fabrication of chitosan films reinforced with parallel aligned graphene oxide

The excellent water solubility of graphene oxide (GO) imparts it feasibility as a new filler for reinforcing hydrophilic biopolymers. In this work, we present a simple and green approach to fabrication of GO/chitosan nanocomposite films. Mechanical properties of the nanocomposite have been significantly enhanced without sacrificing the optical transparency. GO sheets are unidirectionally aligned in the chitosan matrix and parallel to the surface of nanaocomposite film, which has been manifested by the morphological observation and explained by the theoretical prediction of tensile modulus. With incorporation of 1 wt% GO, the fracture strength and tensile modulus of the nanocomopsites are significantly enhanced by 93% and 51%, respectively. The simultaneous improvement of strength and toughness could be attributed to the homogeneous dispersion and alignment of GO sheets in the chitosan matrix, the strong interfacial adhesion between GO and chitosan, as well as the high specific surface area and the two-dimensional geometry of GO.