Effects of 360-kHz ultrasound on aqueous solutions of chitosan and starch were studied. This treatment is an efficient procedure for
reduction of molecular weight of both polysaccharides. It has been demonstrated that at the applied ultrasound frequency degradation is
caused both by OH radicals and mechanochemical effects. In Ar-saturated 2!10K2 mol dmK3 chitosan solutions, pH 3, at an ultrasound
dose rate of 170 W kgK1, the average sonochemical chain scission yield in the sonication time range of 0–90 min is ca. 8!10K11 mol JK1.
This yield has been shown to depend on polymer concentration, ultrasound power and gas used to saturate the solution. Scission is
accompanied by side reactions leading to the formation of carbonyl groups. Ultrasound-induced chain scission of starch proceeds with lower
yield, one of the reasons being probably the different chain conformation when compared with rod-like chitosan macromolecules.
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