Real Time FTIR study on Hydrogen Bonded Complex of Epoxides and Oxetanes in Photo-initiated Cationic Polymerization

The importance of study on photo-initiated polymerization continue to increase, because its understanding and control is a key factor to accurate result of 3D printing. We studied the thermal stability of the hydrogen bonded complex of epoxy and oxetane monomers with Brønsted acid, as being generated during photo-initiated cationic polymerization. In particular, we investigated how its thermal stability affects the induction period in the polymerization. The chemical structure of monomers with glycidyl or methylene ether groups next to epoxy or oxetane groups form an intermediate metastable state of secondary oxonium ions with generated superacid. It stabilizes the photo-acid and is responsible for the induction time in the cationic photo-polymerization. Using temperature-controlled FTIR with in-situ UV irradiation, we performed a series of real-time FTIR (RT-FTIR) experiments to support that the induction time is originated from the thermal stability of the hydrogen bonded complex that is strongly influenced by the heat conduction environment for the study of photo-polymerization.