Initiation of 1,6-hexanedioldiacrylate polymerization by three component photoinitiators incorporating 2,3-dimethylmaleic anhydride

Three component photoinitiators mixtures comprised of benzophenone (BP), 4-benzoylbiphenyl (BBP), or isopropylthioxanthone (ITX) with a tertiary amine and an electron deficient anhydride ene result in rapid photoinitiation rates of acrylate polymerization. Concentrations of less than 0.1 weight percent 2,3-dimethylmaleic anhydride (DMMA) added to 1,6-hexanedioldiacrylate (HDDA) containing any of the aforementioned diarylketones and N-methyl-N,N-diethanolamine (MDEA) results in an increase in the polymerization rate maximum by a factor of as much as three times that attained for samples with only MDEA and BP, BBP, or ITX. Laser flash photolysis results confirm that BP, BBP, and ITX are readily quenched by MDEA and DMMA. An initiation mechanism is proposed.