Microstructure and phase behavior of a semi-interpenetrating polymer network consisting of 10% poly(ethylene oxide) and 90% crosslinked-silicone have been studied using various H-1 solid-state NMR methods under fast magic angle spinning in combination with well-known polymer characterization techniques. Both, H-1 double-quantum MAS NMR spectroscopy as well as NOESY MAS measurements indicate a mixing of the two components on a molecular level.