Photoinitiation of acrylamide polymerization by Fe2O3 nanoparticles

Photocatalytic activity of α-Fe2O3 nanoparticles in the acrylamide photopolymerization in aqueous solutions has been investigated. The photoreaction proceeds efficiently both in degassed and air-exposed solutions, at low photoinitiator concentrations ([Fe2O3] < 1 × 10−3 M), under the near UV and the visible light (λ < 600 nm), and results in the formation of polyacrylamide with relatively high molecular mass (1.2 × 106 g/mole in degassed solutions and 0.7 × 106 g/mole in air-exposed solutions).Kinetics of the photoinduced acrylamide polymerization has been studied and optimal reaction conditions determined. It has been shown that the quantum yields of the photopolymerization and the photoinitiation in the systems under investigation do not exceed, respectively, 102 and 10−2.The mechanism of the photopolymerization has been proposed, which includes the photoinitiation stage with the participation of acrylamide radicals, the latters originating from the monomer oxidation by the photogenerated Fe2O3 valence band holes, the free-radical chain growth and subsequent recombination of the growing macroradicals.