Simultaneous free radical and cationic photopolymerizations of mixtures of multifunctional acrylate and oxetane monomers were carried out to provide hybrid interpenetrating network polymers. The use of kick-started oxetanes in which oxetane monomers are accelerated by the use of small amounts of certain highly substituted epoxides provides dual independent radical and cationic systems with similar rates of photopolymerization leading to homogeneous interpenetrating networks. The combined photopolymerizations are very rapid and afford crosslinked network films that are colorless, hard, and transparent. The networks display no indications of phase separation. The use of this technology in various applications such as coatings, 3D imaging, and for composites is discussed. (c) 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 594-601