Light scattering studies of the sol-to-gel transition in particulate systems

We present investigations of the kinetics of the colloidal sol-to-gel transition by combining small angle static light scattering (SASLS) and dynamic light scattering (DLS) techniques. Dilute monomer volume fractions were used to allow for a full investigation of the gelation to obtain all possible kinetic regimes. Our data verify the predictions of a kinetic theory, the ideal gel point (IGP) theory, where three regimes of kinetics are expected. We observe the first regime, the well-known cluster-dilute regime, with a kinetic exponent of z = 1. Followed by a cluster-dense regime with an enhanced kinetics and z ≃ 2. Finally, a gelation regime is observed where the aggregate growth slows and ceases to grow at the IGP predicted size, R_g,G. These results quantitatively verify the IGP theory. We conclude that kinetic description provides a complete theory of the gelation process from sol to gel.