Stability and aging of solubilized dialdehyde cellulose

Derivatization of alpha cellulose by periodate oxidation is an useful method for production of dialdehyde cellulose (DAC). Conversion of the 2,3-hydroxyl groups to a pair of aldehyde groups along with cleavage of the C2–C3 bond of anhydroglucose unit reduces crystallinity of initial material, leaving DAC soluble in water under mild conditions. Solubilization in hot water is necessary to obtain product in solution. The first part of our work confirmed that solubilization causes severe degradation of the molecular weight of the polymer. However, the chemistry and processes within these solutions are currently poorly understood. In the main part of the study, products of periodate oxidation were identified in acidic DAC solutions by NMR spectroscopy for the first time. Subsequent investigation of the acidic DAC solution's aging demonstrated that the low pH of the DAC solution considerably slows the degradation processes, namely the decrease of reactive aldehyde group content when compared to previous studies. Large increase in the molecular weight, observed after 14 days of aging, was explained by formation of intermolecular hemiacetals. Our results demonstrate that pH-stabilized aqueous DAC solutions remained active (e.g. applicable for cross-linking reactions) even several weeks after preparation, therefore reducing the need to prepare a fresh solution each time.