Dilution effect on the cluster growth near the gelation threshold

Abstract

Cluster growth process during the gelation is attractive from both scientific and biomedical point of views. Until now, there have been many attempts from theoretical and experimental approaches. However, the comparison of the experimental results with the theoretical prediction is ambiguous, because it is impossible to quench the gelation reaction and directly estimate the connectivity in experiments. In this study, we fabricated the states near the critical points using the Tetra-PEG gel system with off-stoichiometrically mixing. We estimated the connectivity directly using the NMR measurement. Using this system, we performed the DLS and viscosity measurements to discuss the cluster growth. The cluster size increase with approaching the gelation critical point showing the characteristic scaling relationship. The scaling exponent depended on the polymer concentration at preparation. At the high concentration region, the exponent agrees with the prediction of the percolation theory. While it downwardly deviates from the prediction in low concentration, which suggests the lattice approximation is failed below the overlapping concentration.