Dispersibility of Nanocrystalline Cellulose in Organic Solvents

Aqueous suspensions of nanocrystalline cellulose (NCC) were obtained by sulfuric acid hydrolysis using the standard procedure. Suspensions, films, and aerogel of NCC were characterized by various methods: the degree of polymerization was determined, elemental analysis was carried out, the degree of crystallinity and crystallite size were calculated on the basis of X-ray data, and the morphology of NCC aerogels was studied using scanning electron microscopy. The particle size of the NCC was determined using a transmission electron microscope, a scanning atomic force microscope, and the method of dynamic light scattering. NCC hydrosols with different pH were used to prepare lyophilized NCC samples. From NCC hydrosols with pH 2.2, by gradual replacement of water with an organic solvent, NCC organogels with acetone, acetonitrile, and ethanol were obtained. The dispersion of lyophilized NCC and NCC organogels (acetone, acetonitrile, and ethanol) in water and in 11 organic solvents was investigated. The effect of the pH of the initial aqueous suspension of the NCC and the solvent forming the NCC organogel on the repeated dispersibility of the NCC is shown. The optimum pH value of the initial aqueous suspension of NCC was determined, which determines the maximum dispersibility of the lyophilized samples in each specific solvent. Acetone, acetonitrile, and ethanol organogels are dispersed in most of the solvents studied with the formation of particles less than 100 nm in diameter.