Diazobenzo[a]fluorene derivatives as visible photosensitizers for cationic polymerization

Photoredox pairs consisting of dyes based on diazobenzo[a]fluorene derivatives and commercially available onium salts (diaryliodonium and triphenylsulfonium salts) are tested as effective initiator systems for the cationic polymerization of cyclohexene oxide using visible light. The efficiency of these initiator systems is discussed based on the free energy change for the electron transfer from examined dyes to the onium compounds. The most efficient sensitizers are the dyes with the lowest oxidation potential and the highest −ΔGel. A linear relationship between the quantum yields of acid release Φ(H+) and the conversion of CHO is observed.