Simultaneous Reinforcement and Toughening of Carbon Nanotube/Cellulose Conductive Nanocomposite Films by Interfacial Hydrogen Bonding

Carbon nanotube (CNT)/cellulose nanocomposite films were prepared by a featured processing method, i.e., solution dispersion, slow gelation and hot-press drying, where an environmentally benign processing solvent (sodium hydroxide/urea aqueous solution) was used. The scanning electron microscopy and transmission electron microscopy demonstrated uniform CNT dispersion in the cellulose. The slow gelation and hot-press drying could effectively reduce the free volume and force the cellulose chains and CNTs to contact as close as possible, thus forming the strong interfacial hydrogen bonding between the residual oxygen-containing functional groups on the CNT surfaces and the hydroxyl groups in the cellulose chains, as confirmed by X-ray photoelectron spectroscopy and Fourier transformation infrared spectroscopy results. As a result, with a CNT loading of 5 wt %, the tensile strength and Young's modulus of the cellulose nanocomposite films were increased by 55% and 21% relative to neat cellulose film. More interestingly, the tensile toughness reached 5.8 MJ/m3, about 346% higher than that of neat cellulose film. This simultaneous reinforcement and toughening of cellulose by only incorporating the pristine CNTs has been rarely reported. The reason could be explained in the terms of the fortified interfacial hydrogen bonding, which not only facilitated the stress transfer in the interfacial region but also reduced the density of hydrogen bonding network in the intra- and intermolecular chains of cellulose so as to enhance the plastic deformation of the cellulose nanocomposite films significantly. In addition, a good conductivity of 7.2 S·m–1 was achieved with a percolation threshold of as low as 0.71 vol %. The strategy proposed here is simple, low cost, efficient and "green", exhibiting great potential for fabricating high-performance and multifunctional CNT/cellulose nanocomposite films used in the realms of antistatic packages, electromagnetic shielding, electrodes, sensors and electric smart brands.