Diethoxy-azobis(pyridinium) salt as photoinitiator for cationic polymerization:: Towards wavelength tunability by cis-trans isomerization

N,N'-diethoxy-4,4'-azobis(pyridinium) hexafluorophosphate (DEAP) has been synthesized by alkylation of the corresponding N-oxide and characterized. DEAP exhibits UV induced cis-trans isomerization with absorptions at around lambda = 459 and 360 nm, respectively. The ability of the DEAP ion to act as a photoinitiator for the cationic polymerization of cyclohexene oxide and N-vinylcarbazole is demonstrated. The initiation step involves the decay of the excited state of the trans form of the salt with homolytic bond rupture of the nitrogen-oxygen bond. Its potential use as a photoinitiator for free radical polymerization is also demonstrated using methyl methacrylate monomer as the example.