Cationic and radical polymerization using a boron-thienothiophene-triphenylamine based D-π-A type photosensitizer under white LED irradiation

A donor-π-acceptor type photoinitiator, composed of boron-thienothiophene-triphenylamine (DMB-TT-TPA) to be used as a synthesizer under white LED irradiation, was studied for cationic and radical polymerization of mono and difunctional monomers. The monomers methyl methacrylate (MMA), styrene (Sty), cyclohexene oxide (CHO), isobutyl vinyl ether (IBVE), triethylene glycol dimethacrylate (TEGDMA) and bisphenol A diglycidyl ether (BADGE) were exposed to irradiation under a white LED source in CH₂Cl₂ with DMB-TT-TPA, in the presence of diphenyliodonium hexafluorophosphate (DPI). Of the spectroscopic techniques, fluorescence was used to investigate the photophysical characteristics of DMB-TT-TPA to gather data that would be helpful in affirming the initiation process. The presence of the synthesizer in all the polymer structures was proved by NMR spectroscopy studies. The importance of the described photoinduced electron transfer process with respect to the initiation of radical and cationic polymerizations and formation of conjugated polymers was demonstrated.