Hydrogels

Hydrogels are crosslinked polymers with the ability to swell in an aqueous medium. Crosslinking in hydrogels occurs by chemical or physical means depending on the polymer properties and experimental conditions. Owing to a large variety in chemical structure and crosslinking methods, various hydrogels have been prepared for various applications in pharmaceutical and biomedical fields. This chapter begins with hydrogel classification, properties, and their methods of preparation. The chapter continues with intelligent hydrogels, which are able to respond to environmental changes such as temperature, pH, and solvent composition, by changing their dimensions. Hydrogel based on polysaccharides, hydrocolloids, and synthetic polymers are discussed accordingly. Finally, the chapter concludes with known hydrogel applications in the pharmaceutical area. These include superdisintegrants, ion exchanging resins, superporous hydrogels, hydrogel implants, hydrogel inserts, osmotic products (devices, implants, and tablets), as well as tissue expanding hydrogels and contact lenses.