Connectivity dependence of gelation and elasticity in AB-type polymerization: an experimental comparison of the dynamic process and stoichiometrically imbalanced mixing

To control various physical properties of polymer gels, it is important to control the connection probability between functional groups of network structures (connectivity). In this study, we compare two methodologies tuning the connectivity in AB-type polymerization: one is stopping the reaction intentionally at a certain conversion, and the other is mixing two prepolymers in a stoichiometrically imbalanced ratio. By experimentally examining the relationships between elastic modulus and connectivity, we find that the relationships are almost the same for these two methodologies. However, the critical connectivity for gelation is different. These results are well reproduced by a kind of phantom network model whose structural parameters are estimated by using a mean-field approximation.