Traditional and gradient interpenetrating polymer networks (IPNs) of various composition have been prepared on the basis of crosslinked siliceous polyurethane and a copolymer of butylmethacrylate and dimethacrylate triethylene glycol. For various layers of gradient IPNs cut from the surface to the center of the sample detailed investigations by methods of volume dilatometry, vapor sorption and broadband ac dielectric relaxation spectroscopy were carried out. From data of benzene vapor sorption by various layers of gradient IPN the free energy of mixing of the IPN components has been calculated. For all the layers the free energies of mixing are positive and depend on the distance from the sample surface. Each layer consists of two phases with their own transition temperatures. From these data the composition of each phase for various layers has been calculated. The dipolar Lu mechanism of the polyurethane-rich phase and the ac conductivity mechanism were studied in detail by analyzing the dielectric susceptibility data within the complex permittivity and the modulus formalism.