Preparation of high-aspect-ratio cellulose nanocrystals by solvothermal synthesis followed by mechanical exfoliation

Abstract

We report a green chemical–physical approach for extracting cellulose nanocrystals (CNCs), using a two-step collaborative process combining solvothermal pretreatment and mechanical exfoliation. This method avoids the use of large volumes of sulfuric acid. The structure, morphology, size distribution, zeta potential, crystallinity, and thermal stability of the CNCs are characterized by Fourier-transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and scanning electron, transmission electron and atomic force microscopies. The yield and properties of the obtained CNCs are investigated and compared with those obtained by the conventional acid hydrolysis method. A yield of 72.17 ± 2.00% was obtained, which was significantly higher than that of 30–35% for the traditional sulfuric acid hydrolysis method. CNCs are obtained with an aspect ratio of 25 times, average length of 280 nm, and average width of 11 nm. The CNCs obtained by the two-step process exhibit better thermal stability than those obtained by the conventional acid hydrolysis. The combination of solvothermal pretreatment and mechanical exfoliation is an efficient and promising method for the large-scale production of CNCs for industrial application.