New ternary polymer electrolytes based on a commercial cross-linking resin dianol diacrylate (DDA), tetramethylene sulphone (TMS) as a compatibilizing solvent and ionic liquids (ILs) were prepared by in situ photopolymerisation. The electrolytes containing two polymer-to-TMS-to-IL ratios, 20:30:50 and 20:20:60 by weight, respectively and six various ILs were investigated. The obtained materials were flexible, self-standing with good mechanical properties and a long-term stability. They showed high ionic conductivities, in the range of ca. 7×10−3 to 3×10−2 Scm−1 at 25°C. A very important result is that the conductivities of all the prepared polymer electrolytes exceeded the conductivities of the corresponding neat ILs by 2–3.5 times. The temperature dependence of the ionic conductivity correlates with VTF equation. All the materials prepared were characterized by a broad electrochemical stability window (3.3–3.7V).