Preparation and characterization of sterically stabilized nanocrystalline cellulose obtained by periodate oxidation of cellulose fibers

We produced novel nanocellulose particles made from cellulose fibers by periodate oxidation. For partial oxidation [degree of substitution (DS) <2], three products were generated after the periodate oxidized fibers were heat treated: fibrous cellulose, rod-like dialdehyde cellulose (DAC) nanofibers which we refer to as sterically stabilized nanocrystalline cellulose (SNCC), and dissolved DAC which is a copolymer of cellulose and DAC which we refer to as dialdehyde modified cellulose (DAMC). The products were separated by centrifugation and cosolvent addition. SNCC has similar dimension (100-200 nm in length and 5-8 nm in width) as conventional nanocrystalline cellulose (NCC) made by sulfuric acid hydrolysis. Several techniques were applied to characterize SNCC and its properties are compared to NCC. DAMC was found to be soluble in hot water or a few solvents (such as dimethyl formamide and dimethyl acetamide) at elevated temperature, but was insoluble in most common solvents at room temperature. The molecular weight of DAC (DS = 2) produced under various conditions (heating time and temperature) was determined by gel permeation chromatography. It was shown that the molecular weight decreased from 85.1 to 4.1 kDa with heating time and residence time when cooled down to room temperature.