2003 Volume 36 Issue 6 Pages 716-719
Chitosan gel particles were prepared by the suspension evaporation method in which various gelation conditions, such as acid media to dissolve the chitosan flake, gelation temperature and crosslinking degree were controlled. The gelation of the chitosan solution of strongly acidic (hydrochloric acid) media could not be observed at any gelation temperature. On the other hand, in the chitosan solution of weakly acidic media such as acetic and adipic acid, the gelation occurred at a temperature between 348 and 358 K. The amount and pKa values of amino groups in the gel particles were analyzed by an acid-base titration method and dissociation property of the amino groups was evaluated. The pKa of the amino groups in the chitosan gel particles was low compared with that of the original chitosan polymer. It was demonstrated that dissociation curves of the gel particles shifted toward a much lower pH region increasing their crosslinking degree, that is, the formation of three-dimensional polymer networks.