Voltammetric characterization on the hydrophobic interaction in polysaccharide hydrogels

Cyclic voltammetric (CV) investigations on the properties of microdomains in polysaccharide hydrogels, methyl cellulose (MC) and kappa-carrageenan (CAR), coated on glassy carbon electrodes were reported in which methylene blue (MB), tris(1,10-phenanthroline)cobalt(III) (Co(phen)3(3+/2+)) cations, and ferricyanide/ferrocyanide (Fe(CN)6(3-/4-)) anions were used as electroactive probes. Information on the patterns and strength of intermolecular interactions in these polysaccharide hydrogels can be inferred from the net shift of normal potentials (E degrees'), the change of peak currents (ip), the ratio of binding constants (K(red)/K(ox)) for reduced and oxidized forms of bound species, and the apparent diffusion coefficients (D(app)) of probe in hydrogels. The transition of hydrophobic interaction in MC hydrogel with temperature was manifested by the CV method, which is in agreement with the evolution of the storage modulus (G') during gelation. It was also found that, in addition to inducing the change of E degrees' and ip of these probes used, the hydrophobic-hydrophilic nature of the microenvironment in hydrogels coated on the substrate electrodes greatly influenced the peak-peak separation (DeltaEp) of MB and the redox reversibility of Fe(CN)6(3-/4-) via modulation of both the heterogeneous electron-transfer process at the gel-substrate interface and the charge-transfer process in hydrogels. The results imply that the CV method is of significant benefit to the understanding of the gelation driving forces in the polysaccharide hydrogels at a molecular level.