Real-time fluorescence measurements have been developed for measuring the fractal dimension $d_f$ and critical exponents $\gamma$ and $\beta$ simultaneously during the sol-gel transition of acrylamide bisacrylamide cross-linking copolymerization. We observed that $d_f$ passes through a minimum value of $\sim 2.5$ at a critical time $t_c$ and crossover to 3 above it. The exponents $\gamma$ and $\beta$, measured at $t_c$, were found to be around 1.8 and 0.45, respectively. All parameters $d_f$, $\beta$, and $\gamma$ measured at the critical point $t_c$ agree with three-dimensional percolation results.

• Received 3 March 2008

DOI:https://doi.org/10.1103/PhysRevE.77.051121