A new facile and efficient strategy for high-yield preparation of spherical cellulose nanocrystals via enzymolysis-mechanical synergy

This study presents an easy, low-cost, high-yield fabrication method for spherical cellulose nanocrystals (SCNCs) from raw celluloses of eucalyptus pulp (EP) and microcrystalline cellulose (MCC) via a synergetic strategy of swelling-enzymolysis-mechanical treatment. The effects of swelling, enzymolysis, and homogenization on the morphology and properties of the SCNCs obtained from the two raw celluloses were systematically investigated. In comparison with the method that only resulted in low-yield (at most 8%) SCNCs from the supernatants prepared by swelling and enzymolysis of raw celluloses in sequence or simultaneously, high-yield, well-dispersed SCNCs with a high purity of more than 98% was obtained by high-pressure homogenization of centrifugal precipitates of the swollen and enzymatically hydrolyzed raw celluloses. The total yields of SCNCs with diameters of 20-50 nm were ca. 72% and 74% from EP and MCC, respectively. The deconvolution fitting of FT-IR showed that the inter-molecular and intramolecular hydrogen bonds related to O(6) within the anhydroglucose unit of cellulose were largely destroyed in the process of enzymatic hydrolysis, which was closely associated with the degradation of partial crystalline regions by endonu-clease under high enzyme activity, thus promoting the depolymerization of cellulose and the formation of SCNCs. The crystal structure of the resulting SCNCs did not change. In particular, compared with SCNCs from EP, the SCNCs obtained from MCC possessed high crystallinity (88.5%), thermal stability (decomposition temperature, 341.7 degrees C), and hydrophobicity. The unique morphology and excellent properties of SCNCs may broaden the application of cellulose-based nanomaterials in high value-added fields. [GRAPHICS] .