A study of the photoactivities and thermomechanical properties of epoxy resins using novel [cyclopentadien-Fe-arene]+PF6− photoinitiators

The cationic photopolymerization of epoxy resins, initiated by novel cyclopentadien-Fe-arene hexafluorophosphate ([cyclopentadien-Fe-arene]+PF6−), has been investigated. The influence of different photoinitiators and the presence of different epoxy monomers on the rate of photopolymerization and on the thermomechanical properties of the UV-cured film obtained had been studied. Using [cyclopentadien-Fe-biphenyl]+PF6− (CFB) as photoinitiator, the photoactivity increased obviously when cycloaliphatic epoxy monomer 3,4-epoxycyclohexylmethyl-3′,4′-epoxycyclohexane carboxylate (ERL-4221) was added in epoxy resin (E44), but the film obtained is micro-heterogeneous. However, in spite of the lower activity, the film from glycidylether 1,2,3-(2,3-epoxypropyl)-glycidylether (EPON-812) + E44 is homogeneous. The film obtained from di(2,3-epoxypropyl)3,4-epoxy-1,2-cyclohexanedioate (TDE-85) + E44 possesses the highest glass transition temperature Tg. Photoinitiators can influence the properties of the resulting epoxy resins, including the rigidity, crosslink density, Tg and homogeneity. The resulting epoxy resin initiated by [cyclopentadien-Fe-toluene]+PF6− (CFT) with lower photoactivity got the highest crosslink density. Initiated by [cyclopentadien-Fe-diphenylether]+PF6− (CFD) and [cyclopentadien-Fe-anisole]+PF6− (CFA) with greater solubility, the compatibility of epoxy ERL-4221 and E44 can be improved.