Interpenetrating polymer network (IPN) hydrogels based on poly(vinyl alcohol) (PVA) and 1-vinyl-2-pyrrolidone (VP) were prepared by radical polymerization using 2,2-dimethyl-2-phenylacetophenone (DMPAP) and methylene bisacrylicamide (MBAAm) as initiator and crosslinker, respectively. The thermal characterization of the IPNs was investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dielectric analysis (DEA). Depressions of the melting temperatures of PVA segments in IPNs were observed with increasing VP content via the DSC. The DEA was employed to ascertain the glass transition temperature (T-g) of IPNs. From the result of DEA, IPNs exhibited two T(g)s indicating the presence of phase separation in the IPN. The thermal decomposition of IPNs was investigated using TGA and appeared at near 270degreesC,