(eta 6-Carbazole)(eta 5-cyclopentadienyl) iron hexafluorophosphate salts (CFS PF6) are capable of photoinitiating cationic polymerization of epoxy monomers directly upon irradiation with long-wavelength UV light. To improve the solubility of CFS ferrocenium salts in epoxides, two CFS photoinitiators; have been prepared: [cyclopentadiene-Fe-N-buylcarbazole] hexafluorophosphate (C4-CFS PF6) and [cyclopentadiene-Fe-N-octylcarbazole] hexafluorophosphate (C8-CFS PF6), bearing C4 and C8 alkyl chains, respectively, on the nitrogen atom. Studies with real-time infrared spectroscopy have shown that C4-CFS and C8-CFS photoinitiators; exhibit high efficiency in polymerization of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate (ERL-4221) epoxy monomer, but lower efficiency in polymerization of di(2,3-epoxypropyl)-3,4-epoxy-1,2-cyclohexanedioate (TDE-85) epoxy monomer. Elenzoyl peroxide (BPO) sensitizer was very effective in improving the photoinitiating activities of CFS in polymerization of both ERL-4221 and TDE-85. DSC studies have shown that C4-CFS and C8-CFS photoinitiators; can also be employed as thermal initiators for the cationic ring-opening polymerization of epoxides at moderate temperatures. POLYM. ENG. SCI., 49:613-618, 2009. (c) 2009 Society of Plastics Engineers