Sol-to-Gel Transition: The Models

Abstract

The sol-to-gel transition is a critical phenomenon which is observed in systems of different nature and composition; several theories with different mathematical approaches have been developed with the main purpose of making a prediction of the gel point. These models have been applied to systems which grow in a stochastic way and to different practical problems. Most of these theories have been used for studying gelation in organic polymers and colloidal systems of particles but they also have been, even if a much smaller extent, applied to inorganic sol-gel systems. Some of these models reach a quite good correspondence with experimental results; in other cases, even if they fail to match with the data they are however an important tool for a basic understanding of the process. The models are also used to make previsions and to find answers to some fundamental questions: when the system will gel, which is the minimum number of reactions (bonds formation) to observe a sol to gel transition?