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SUMMARY: The photo-induced copolymerisation of electron donor/electron acceptor monomers has been studied by real-time infrared spectroscopy. With stoichiometric maleimide-vinyl ether mixtures, the reaction was found to proceed within seconds upon UV exposure. For systems with an excess of vinyl ether, the two monomers disappeared at essentially the same rate, to generate an alternating copolymer. In such photoinitiator-free systems, the initiating radicals are mainly formed by hydrogen abstraction by the excited maleimide molecules. Highly crosslinked polymer networks have been obtained by light-induced copolymerisation of bismaleimide and divinyl ether monomers. One of the distinct characteristics of this type of radical-induced polymerisation, beside the absence of any added photoinitiator, is that it is less sensitive to oxygen inhibition than the conventional UV-curable acrylate resins.