Synthesis and characterization of thermo- and pH-sensitive poly(vinyl alcohol)/poly(N, N-diethylacrylamide-co-itaconic acid) semi-IPN hydrogels.

In this paper, a series of thermo- and pH-sensitive poly(vinyl alcohol)/poly(N, N-diethylacrylamide-co-itaconic acid) (PVA/P(DEA-co-IA)) semi-interpenetrating polymer network (semi-IPN) hydrogels were synthesized by radical polymerization and semi-IPN technology. The influence of PVA on the property of resulting PVA/P(DEA-co-IA) (PVA/PDI) semi-IPN hydrogels was investigated and characterized. The interior morphology observed by scanning electron microscopy (SEM) revealed that freeze-dried semi-IPN hydrogels had small pore size and interconnected porous network structures. X-ray diffraction (XRD) studies showed that a sharp characteristic peak of PVA in semi-IPN hydrogel could be observed at about 2θ = 20°. The incorporation of PVA decreased the equilibrium swelling ratio of modified hydrogels when compared with a usual PDI hydrogel. The semi-IPN hydrogels exhibited unconventional thermosensitive characteristics, such as faster deswelling rates and slower swelling rates in response to temperature change, and excellent mutative values in response to an alternation of the pH value, the changing degree of which depended on the PVA content. The release behaviors of the model drug, aminophylline, were found to be dependent on hydrogel compositions and the environmental temperature. Compared with the usual PDI hydrogel, the drug release rate of the semi-IPN hydrogel is slower, which could be expected to be useful in the biomedical and biotechnology fields.