Frontal polymerization and characterization of interpenetrating polymer networks composed of poly(N-isopropylacrylamide) and polyvinylpyrrolidone

The synthesis of semi-interpenetrating polymer networks (IPN) of the hydrogel, poly(N-isopropylacrylamide)/polyvinylpyrrolidone (PNIPAm/PVP), by frontal polymerization, was carried out. The frontal parameters were studied, and the products were characterized. It was observed that the incorporation of PVP into PNIPAm shortened the response time, without changing the lower critical solution temperature (LCST) of PNIPAm. Furthermore, the compressive strength of IPN hydrogels increased with increase in PVP concentration. Also, the drug release behaviors of IPN hydrogels were explored using the model drug aspirin. It was demonstrated that the drug loading capacity of the hydrogels increased from 245 to 422 mg/g by increasing PVP concentration from 0 to 20%. The drug release data suggested that the drug could be released in an improved and controlled manner by the IPN hydrogels, without the loss of their intelligent properties. All these results indicate that IPNs based on PNIPAm/PVP hydrogels can be finely tuned by frontal polymerization and can be used as drug delivery systems.