Dynamic Light Scattering Analysis on Critical Behavior of Cluster Size Distribution of Polyacrylamide and Agarose Solutions near the Sol-Gel Transition Point

Abstract

The dynamic light scattering (DLS) method was applied to measure the cluster radii of polyacrylamide and agarose solutions near the sol-gel transition point. In the case of polyacrylamide, primary clusters were formed first and secondary clusters on a larger scale were sequentially formed in the progress of the polymerization process. The z-average radius of the secondary cluster near the sol-gel transition point increased divergently with an increase in acrylamide concentration to the transition point. By fitting the data with the scaling law, the sol-gel transition concentration and the critical exponent were determined to be 1.53 % and 0.84, respectively. The z-average radius of the agarose cluster also showed a tendency to diverge with an increase in concentration to the sol-gel transition point. With fitting by the scaling law, the sol-gel transition concentration and the critical exponent of the agarose solution were determined to be 4.5×10^-2% and 0.92, respectively, at 27.0°C. Thus, the percolation theory was proved to be effective to describe the cluster size distributions near the sol-gel transition point for both polyacrylamide and agarose solutions.