Effect of sonochemical treatments on the integrity and oxidation state of cellulose

The sonochemical degradation of cellulose by a 24-kHz ultrasound probe system and the oxidative modification of cellulose upon sonication were studied. Both aqueous cellulose suspension (heterogeneous system) as well as cellulose solutions in N,N-dimethylacetamide/LiCl (homogeneous system) were used. In both cases, a significant reduction in the degree of polymerization was observed. The rate of the degradation process was dependent on the degree of polymerization of the starting material, temperature, cellulose amount in suspension, cellulose concentration in solution, and the pH value of the aqueous suspension. In solution, the degradation process was accompanied by cellulose oxidation as seen in the introduction of carbonyl groups. The introduction of carbonyl groups could be shown to occur close to chain ends. Sonochemical degradation of cellulose is a very efficient non-classical method in accordance with "green chemistry" concepts.