Chitosan cross-linked with Mo(VI) polyoxyanions: a new gelling system

A procedure for preparing homogeneous chitosan gels by in situ molybdate cross-linking is described. The gels are obtained by dispersing solid MoO3 in a buffered chitosan solution and the polymer is cross-linked by formation of heavily negatively charged molybdate polyoxyanions. The resulting ionic gels are very transparent, thermoirreversible and can be made at low polymer concentrations. Depending on the ionic strength, these gels are able to swell several times their original size in aqueous solutions. Estimates of the degree of cross-linking reveal a very open pore structure which is confirmed by electron micrographs of the gel.