Oxidative Degradation of Chitosan to the Low Molecular Water-Soluble Chitosan over Peroxotungstate as Chemical Scissors

Low molecular water-soluble chitosan was prepared by the depolymerization of chitosan in the presence of a series of catalysts with active W(O 2 ) sites. Both the peroxo species [W 2 O 3 (O 2 ) 4 ] 2- and {PO 4 [WO(O 2 ) 2 ] 4 } 3- showed high efficiency in the degradation of chitosan, indicating that the degradation mechanism did not follow the radical mechanism. That means •OH is not the active species, which has been proven by the fluorescence spectra. H 2 O 2 acted as an oxidant to regenerate the active W(O 2 ) sites in the depolymerization of chitosan. The developed catalyst (TBA) 3 {PO 4 [WO(O 2 ) 2 ] 4 } is recoverable.