Dynamic scaling for gelation of a thermosensitive chitosan-β-glycerophosphate hydrogel

This paper investigates the thermal gelation of a chitosan-beta-glycerophosphate system using rheometry. The gelation, performed for two polymer concentrations, was achieved in isothermal conditions to examine the effect of various temperatures (between 35 and 65 degrees C) on the sol-gel transition. The oscillatory shear data was used to verify the scaling behavior (G' similar to G ''similar to omega(n) ) at the gel point, and the power-law index n was found to be dependent to some extent on chitosan concentration and temperature. The solutions zero shear viscosity (eta (0)) and the gels low frequency modulus (G (e)) were analyzed in terms of the relative distance to gelation time (epsilon). The two properties showed power-law relationships with epsilon, i.e., eta (0) similar to epsilon (-s) and G(e) similar to epsilon(z), and the indexes slightly increased with temperature. The dynamic scaling theory predicts a relationship between the indexes, i.e., n =z/(z +s), and this was in reasonably good agreement with the experimental findings.