All-Cellulose Nanocomposites Reinforced with in Situ Retained Cellulose Nanocrystals during Selective Dissolution of Cellulose in an Ionic Liquid

All-cellulose nanocomposites, with cellulose nanocrystals as the reinforcing phase and regenerated cellulose as the matrix, are prepared by a partial dissolution method in 1-ally-3-methylimidazolium chloride (AmimCl), followed by solution casting. The direct images of many undissolved nanocrystals in cellulose/AmimCl solutions have been observed clearly by conventional transmission electron microscopy (TEM). X-ray diffraction (XRD) also proves that there are original cellulose I crystals in regenerated cellulose films. The nanocomposite films are compact, isotropic and transparent to visible light, and show good mechanical properties as a result of the nanocrystals reinforcement. Using microcrystalline cellulose (MCC) as the raw material, the optimal tensile strength and elastic modulus of nanocomposite films have reached 135 MPa and 8.1 GPa, respectively, by controlling the dissolution temperature and time. This work provides an easy and effective pathway to prepare all-cellulose composites.