Green composite films composed of nanocrystalline cellulose and a cellulose matrix regenerated from functionalized ionic liquid solution

By using the excellent selective solubility of the hydroxyl functionalized ionic liquid, 1-(2-hydroxylethyl)-3-methyl imidazolium chloride ([HeMIM]Cl), to the pretreated microcrystalline cellulose (PMCC) and nanocrystalline cellulose (NCC), a green all-cellulose nanocomposite film, in which both the fibers and the matrix are cellulose, was easily prepared via adding NCC to the cellulose ionic liquid solution. It was found that the PMCC can be efficiently dissolved in [HeMIM]Cl, whereas NCC slightly dissolved in it. The morphology, crystalline structure, thermal stabilities, mechanical and optical properties of the as-prepared film were characterized by X-ray diffraction (XRD), thermal gravimetric analysis (TGA), scanning electron microscope (SEM), optical transmittance and mechanical testing. The nanocomposite films showed good optical transparency, thermal stabilities and mechanical properties as the result of reinforcement by increasing the content of NCC. But, with the content of NCC increased from 5% to 25%, the decomposition temperature and elongation at break decreased obviously. This work demonstrated a promising route for the preparation of biodegradable green all-cellulose nanocomposites. In addition, this all-cellulose nanocomposite composite is composed of sustainable biodegradable resources, which give it to be benign to environment.