Strong, tough, and ductile biocomposite from noncovalently functionalized cellulose nanofiber/graphene nanoplatelets hybrid and their structure-property relationship

Abstract

A self-assembled cellulose nanofiber (CNF)/graphene nanoplatelets (GNP) biocomposite nanopaper was fabricated with high toughness, ductility, and tensile strength, via noncovalent functionalization with extremely low GNP concentrations of 0.25%, 0.5%, 1%, 2% and 5%. GNP functions as a ball bearing lubricating agent that partially blocks some of the hydrogen bonds while introducing noncovalent C–H···π interactions between the aromatic GNP and the hydrophobic domain of CNF. The produced composite nanopapers possess excellent mechanical properties, and the structure properties co-relationship was established by a combination of Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), wide-angle X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and tensile testing. FESEM results conveyed the formation of a layered fibrous network structure. Raman spectra confirmed the noncovalent functionalization, while XRD analysis highlighted cellulose crystal size modification and reduction in crystallinity owing to the hydrogen bonds alteration, and the interfacial interactions are supported by the FTIR results. These interfacial interactions resulted in controlled fibril slippage and repeated rupture and reformation of hydrogen bonding during mechanical testing leading to simultaneous improvement of toughness, ultimate tensile strength, and strain-to-failure of 34.1 ± 1.8 MJ/m3, 158.3 ± 4.5 MPa, and 35 ± 2.5%, corresponding to improvements of 210%, 47%, and 191%, respectively.