Static Inhomogeneities in Thermoreversible Gels

Abstract

The effect of cross-linking on static inhomogeneities in a thermoreversible polymer gel was investigated by light scattering. Speckle patterns of poly(vinyl alcohol)-Congo Red ion complexes in an aqueous solution were measured at a temperature range between 20 and 60°C. The system changed from the gel state to the sol state in the vicinity of 45°C. An interesting feature was disclosed; the formation of gel leads to a remarkable increase in the spatial fluctuations of scattered intensity (I(q)). By comparing these results with those for a chemically cross-linked gel, it was concluded that the increase in I (q) is solely due to the restricted ergodicity of gels as a result of introducing cross-links to the system.