Gel Network Structure of Methylcellulose in Water

Abstract

Thermal gelation was studied for aqueous gelling solutions of a methylcellulose. An attempt was made to elucidate the gel network structure and the validity of scaling laws. Thermal gelation was observed on heating, and it reverted to the liquid state on cooling. The thermoreversibility was a heating/cooling rate dependent process. For isothermally stabilized samples, 42.5 °C was found to be the critical temperature differentiating the weak gels from the strong gels. Below 42.5 °C, the gel elasticity evolved by following a scaling law with temperature as G e ∼ [( T − T c )/ T c ] 2.93 where G e is the equilibrium modulus of the gel and T c is the critical temperature of 42.5 °C. In contrast, no single scaling laws could be found for G e when the temperature was above 42.5 °C. In the temperature range from 42.5 to 70 °C, it was observed that the elasticity evolution was a linear function of temperature and the mean bridge length between junctions was independent of temperature. On the basis of the experimental results, we proposed the gel network structure formed from the methylcellulose, which consists of hydrophobically associating domains as the junctions and the mean chain length of 2.75 × 10 4 g/mol as bridges connecting the junctions.