Green Fabrication of Regenerated Cellulose/Graphene Films with Simultaneous Improvement of Strength and Toughness by Tailoring the Nanofiber Diameter

The development of green and facile synthesis techniques for flexible, transparent, and conductive films (FTCFs) is in great demand with the rapid consumption of electronics. Herein, we report the environmentally friendly and one-pot fabrication of regenerated cellulose nanofibers (CNFs)/graphene FTCFs directly from raw materials of cellulose and graphite based on ionic liquid. Prepared FTCFs exhibit simultaneous and extraordinary improvement of tensile strength (135.4%) and toughness (459.1%) with graphene loading of only 0.1 wt %. In addition to the contribution of graphene sheets as reinforced filler, the morphology analysis reveals that the diameter size of regenerated CNF plays the key role in tailoring the mechanical properties of regenerated CNF/graphene film. Meanwhile, our results show that the diameter of regenerated CNF is dependent on the dispersion state of graphene sheets. The disruptive self-assembly of cellulose molecules in the regeneration process induced by the hydrophobic interaction between graphene sheets and cellulose chains is proposed to explain the reduction of diameter size of regenerated CNF in the presence of graphene. The high performance FTCFs fabricated by such a simple and green strategy have potential in large-scale industrial applications.