The concomitant cationic polymerization of an epoxy resin and a hybrid monomer is a new concept for toughening epoxy resins. Thermolatent super acids are superior initiators of twin monomer polymerization and copolymerization. Determination of gel yield and instrumental characterization of the formed complex polymer network indicate that copolymerization occurs, integrating the linear silicone and novolak formed during twin polymerization into the epoxy network. (C) 2013 Elsevier Ltd. All rights reserved.