Elimination of inter- and intramolecular crosslinks of phosphorylated chitosan by sodium salt formation

Inter- and intramolecular crosslinking is the main cause of the water insolubility of phosphorylated chitosan synthesized with a phosphorus pentoxide/methanesulfonic acid system. The goal of this study was to eliminate inter- and intramolecular crosslinks and synthesize water-soluble phosphorylated chitosan. Two main factors for the formation of inter- and intramolecular crosslinks are W electrostatic interaction between amino groups and methanesulfonic acid salt and (ii) electrostatic interaction between ammonium groups and phosphoric groups. The influences of ethanol washing and sodium salt formation on the elimination of inter- and intramolecular crosslinks were investigated. Sodium phosphorylated chitosan was water soluble. The solubility was independent of the degree of phosphoric substitution. Polymer Journal (2010) 42, 148-156; doi:10.1038/pj.2009.317; published online 23 December 2009