Morphology Study of IPN-PNIPAAm Hydrogels

Hydrogels are 3-D polymer networks that absorb water but don’t dissolve in water. They show many potential applications in biomedical and biotechnological fieldsincluding drug delivery, enzyme immobilization, and gene carriers due to their high hydrophilicity, biocompatibility, and similarity to natural tissues. Stimuli-sensitive hydrogels, which exhibit volume or phase transitions in response to slight environmental changes, such astemperature, pH, ionic strength, light, electric and magnetic fields, etc., are called intelligent materials (1-3). Among the intelligent hydrogels, crosslinked poly (NIsopropylacrylamide)(PNIPAAm) and its derivatives are typical thermosensitive hydrogels with lower criticalsolution temperature (LCST) around 33°C, below whichthe PNIPAAm hydrogel swells and retains abundant water within its matrix (1, 4) .This transition, is mainly controlledby the hydrophobic interactions among the pendant groups along the PNIPAAm chains. This thermoreversible property of phase separation of PNIPAAm hydrogel has been widely used in many devices (4). In this study, thermosensitive poly (N-Isopropylacrylamide) (PNIPAAm)hydrogel with an interpenetrating polymer network (IPN) structure was prepared by a developing method forcomparison its response rate to temperature, deswelling kinetics, and interior morphology with a conventional PNIPAAm hydrogel.