A mechanistic and laser flash photolysis investigation of acrylamide polymerization photoinitiated by the three component system safranine-T/triethanolamine/diphenyliodonium chloride

The photopolymerization of acrylamide (AA) initiated by the synthetic dye safranine-T in the presence of triethanolamine (TEOHA) as co-initiator has been investigated in aqueous solution. It was found that the addition of diphenyliodonium chloride (DPIC) to the system has a marked accelerating effect on the polymerization rate. In the absence of DPIC an inhibiting effect of TEOHA is observed at high concentrations of the amine. This effect is suppressed by the presence of the onium salt. At the same time the photobleaching of the dye caused by the amine is suppressed by the presence of AA or DPIC. Laser flash photolysis experiments show that the presence of the onium salt increases the yield of triplet state of the dye. Also the yield of radicals in the quenching of the dye triplet by TEOHA increases by the presence of DPIC. The semi-reduced form of the dye decays faster in the presence of DPIC, suggesting a possible way of generating extra active radicals at the same time that the dye is regenerated. It is concluded that are several factors that contribute to the accelerating effect of DPIC on the polymerization rate.