Abstract
The scaling law derived from the percolation theory was applied to the concentration dependence of mechanical properties of polyacrylamide measured near the sol-gel transition point. The critical concentration of the sol-gel transition, φg, was estimated from the plot of concentration (φ) vs. the reciprocal of viscosity (η) by extrapolating 1/η to zero. The critical exponent for the sol viscosity, s, which was estimated from the slope of the log(φg-φ) vs. log η plot was about 0.7. The estimated value of s was similar to the value predicted by the percolation theory based on the superconductor-normal conductor mixture model. The critical exponent for the gel elasticity, t, was estimated from the slope of the log(φ-φg) vs. log G' plot, where G' was the dynamic shear modulus of the gel at a frequency of 2Hz. The value of t was about 2, which was also similar to the value predicted by the percolation theory. These results indicated that the concentration dependences of η and G' of polyacrylamide near the sol-gel transition point were described by the percolation theory.
