Polyelectrolyte complex materials from chitosan and gellan gum

The formation of polyelectrolyte complexation (PEC) films by dipping free-standing films of either gellan gum (GG) or chitosan (CH) into solutions of opposite charge is reported. It was shown that the composition and mechanical characteristics depend on pH, and the order in which the biopolymers were added, i.e., dipping CH into GG, or dipping GG into CH. Toughness, tensile strength, extensibility and density values of PEC films prepared by immersing CH films into GG solutions increased with increasing CH:GG ratio. This was not observed for PEC films prepared by dipping GG into CH. The observed behaviour is attributed to the difference in their film compositions, i.e., films prepared by dipping GG into CH solution consist of an inner CH layer and two outer GG layers. In contrast, GG appears to diffuse into the CH layer for films prepared by dipping CH into GG.