Historical view of hydrogel characterization

Hydrogels are three-dimensional polymeric networks whose main feature is their ability to absorb and retain a large amount of water. This property is mainly due to the structure of their network and varies according to the network parameters. Therefore it was very important for researchers to determine different parameters in order to explain synthesized hydrogel’s behavior. Nowadays, characterization techniques are based on developing machines such as dynamic rheometers, established on the behalf of mathematical and physical theories. However, before the appearance of such equipment, network properties were estimated using, for example, sol–gel analyses such as the Charlesby–Pinner method. In this chapter, we describe the historical methods used for hydrogel network characterization and discuss their efficiency compared to current techniques.