Photolysis and thermal active polymerization of bis (benzylidene) based benzoxazine monomers

A new class of photopolymerizable benzoxazine monomers has been developed, using photoactive bisphenol derivatives such as bis (4-hydroxybenzylidene)-4-phenyl cyclopentanone and bis (4-hydroxybenzylidene)-4-phenyl cyclohexanone, p-toludine and formaldehyde (37%). The structure of the benzoxazine monomers has been confirmed by Fourier Transform Infra Red spectroscopy (FTIR) and 1H and 13C Nuclear Magnetic Resonance spectroscopy (NMR). Upon photolysis with radiation of 365 nm, the monomers undergo photolysis via [2π + 2π] cyclo-addition reaction, which was confirmed by UV spectroscopy. After photolysis, the benzoxazine monomers were subsequently cured at 200 °C for 2 h. The photo irradiated cured products possessed enhanced glass transition temperature and thermal stability, with an increase in the photodimerization time.

► New class of photoactive benzoxazine monomers has been developed.
► Upon photolysis on 365 nm, the monomers undergoes photolysis via [2π + 2π] cycloaddition reaction.
► The UV irradiated benzoxazine gives a highly thermally stable polybenzoxazine.