The radical induced cationic frontal polymerization (RICFP) of the twin monomer 2,2'-spirobi[4H-1,3,2-benzodioxasiline] (SPIRO) in combination with bisphenol-A-diglycidylether (BADGE) has been developed to fabricate nanostructured hybrid material with domain sizes of 2-5 nm. In one reaction step, an interpenetrating network of phenolic resin, SiO2 and the epoxy resin is formed in a very short time period, initiated by UV light. That indicates that both polymerization reactions take place simultaneously. The influence of monomer composition on molecular structure was investigated by means of solid state NMR spectroscopies. The envisaged nanostructure of the resulting organic-inorganic hybrid materials is proven by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). The thermal properties of the hybrid materials are comparable to "state of the art" materials with the advantage that the silica quantity can be adjusted on demand.