Interpenetrating polymer networks hydrogels

After the term first appeared in the 1960s, interpenetrating polymer network (IPN) hydrogels have received tremendous interest for the combined properties and/or functions of both components, as well as the unusual mechanical performances originating from the topologically interlocked structure. These fundamental characteristics of IPNs have been studied extensively, and diverse IPN hydrogels with versatile functions and/or excellent mechanical properties have been developed. These hydrogels are ideal materials for tough adhesion, soft actuators, artificial organs, and so forth, which greatly broaden the applications of gel materials in biomedical and engineering fields. In this chapter, we strive to review the major progress in IPN hydrogel from the aspects of its definition and development, classification, and functionalities. Representative examples are provided to illustrate the general features and application potentials of these IPN gels. At the end of this chapter, we offer some personal opinions on the future research of IPN hydrogels.