Cationic epoxide/oxetane hybrid films

摘要

Although cationic photopolymerisation of epoxides has a number of advantages over free radical acrylate polymerisation, including low sensitivity to oxygen and 'living' character, it is hardly used industrially, in part because there are few raw materials commercially available, but probably mainly because the polymerisation process is slow. Oxetanes also have high ring strain and the heterocyclic oxygen is more basic than the epoxide oxygen. Consequently oxetanes have been included in epoxide formulations to speed up cure. However, despite this higher reactivity, oxetanes are largely added to epoxide formulations because of their longer induction period in the early stages of the polymerisation process. The authors have previously reported work on organic-inorganic hybrid materials formed from the cationic photopolymerisation of sol-gel-derived cycloaliphatic epoxy oligosiloxane (CAEO) resins, which find use in a number of applications for their high transparency, photopatternability and gas barrier properties, but again the rate of photopolymerisation is relatively slow. This paper reports the photopolymerisation behaviour (especially speed) of CAEO resins with difunctional oxetane monomer (3-ethyl-3-{[(3-ethyloxetan-3-yl)methoxy]methyl}oxetanes (DOX)).