Hybrid Graphenene Oxide/Cellulose Nanofillers to Enhance Mechanical and Barrier Properties of Chitosan-Based Composites

Chitosan-based hybrid nanocomposites, containing cellulose nanocrystals (CNCs),graphene oxide (GO), and borate as crosslinking agents, were successfully preparedby solution-casting technique. The synergistic effect of the two fillers, and the role of thecross-linker, in enhancing the structural and functional properties of the chitosan polymer,was investigated. XPS results confirm the chemical interaction between borate ions andhydroxyl groups of chitosan, GO, and CNCs. The morphological characterization showsthat the GO sheets are oriented along the casting surface, whereas the CNC particles arehomogenously distributed in the sample. Results of tensile tests reveal that the presence ofgraphene oxide enhances the elastic modulus, tensile strength, elongation at break, andtoughness of chitosan, while cellulose and borate induce an increase in the elastic modulusand stress at the yield point. In particular, the borate-crosslinked chitosan-based samplecontaining 0.5 wt% of GO and 0.5 wt% of CNCs shows an elongation at a break value of30.2% and a toughness value of 988 J*m-3 which are improved by 124% and 216%,respectively, compared with the pristine chitosan. Moreover, the water permeability resultsshow that the presence of graphene oxide slightly increases the water barrier properties,whereas the borate and cellulose nanocrystals significantly reduce the water vaporpermeability of the polymer by about 50%. Thus, by modulating the content of the tworeinforcing fillers, it is possible to obtain chitosan-based nanocomposites with enhancedmechanical and water barrier properties which can be potentially used in variousapplications such as food and electronic packaging.