Stability of Soluble Dialdehyde Cellulose and the Formation of Hollow Microspheres: Optimization and Characterization

The poor solubility of raw cellulose greatly limits its applications. Herein, the periodate oxidation of cellulose was conducted to obtain dialdehyde cellulose (DAC), which is a kind of soluble and configurable cellulosic derivative with great potential applications as a functional material. The oxidation of cellulose included a process of exfoliating the cellulose from its original source, and the particle size was reduced after a prolonged oxidation. The dissolved DAC, solubilized in water by heating, showed an obvious Tyndall phenomenon with a strengthening trend with aging, and the molecular weight decreased sharply at the beginning of aging and then tended to be stable after 3 months. A large change in the freeze-dried DAC solutions with different oxidation degrees, ranging from crystal string beading to hollow microspheres, was explicated by layer peeling during oxidation, while the solution was at a steady state after aging. The special structure of DAC, such as the existence of aldehydes with low molecular weight in solution-based processes and the formation of regular hollow spheres after freeze-drying, enabled it to be used in cosmetics, food, wound dressings, and drug carriers.