The photoinitiation of MMA polymerization in the presence of iron complexes

The photoinitiated polymerization of methyl methacrylate (MMA) by Fe(III) complexes was studied in aqueous and organic solvents. Although [Fe(bpy)3]3+ and [Fe(DMSO)6]3+ initiate the polymerization in the presence and absence of co-initiators, polymerization was also observed just dissolving FeCl3 in the solvents. The complexes [Fe(CH3OH)6]3+ and [Fe(MMA)6]3+ initiated the polymerization when irradiated in the visible LMCT band. The photoinitiation by both complexes proceeds by different mechanisms due to the different binding of MMA and methanol to the central atom in the complex. It was found that the methanol complex is more effective in producing initiating radicals than the MMA complex. A good agreement is observed between the experimental reaction rates and those calculated assuming different effectiveness for both complexes.