The development of efficient and earth-abundant alternatives to noble-metal photocatalysts remains an important research focus in controlled radical photopolymerization. In this work, two Schiff base Fe(III) complexes (FeIIISalenH and FeIIISalenEtO) were synthesized and evaluated as photocatalysts for radical photopolymerizations. The FeIIISalenL complexes were characterized by FTIR, UV–vis, fluorescence spectroscopy, MALDI-TOF mass spectrometry, cyclic voltammetry, and molar conductance. Photoinduced polymerizations of methyl acrylate (MA) were conducted to investigate the controlling ability of the FeIIISalenL complexes under LED@365 nm. Phenacyl bromide (Ph-Br) served as the alkyl halide and electron acceptor, whereas ethyl 4-(dimethylamino)benzoate (EDB) acted as the electron donor in the system. Light-driven polymerizations yielded polymers with regulated molecular weight control and uniform distributions. Among the two complexes, FeIIISalenEtO exhibited superior performance, showing enhanced control over chain growth, as evidenced by the moderate polydispersity values. In addition, the water solubility of these complexes enables the photopolymerization of 2-hydroxyethyl methacrylate (HEMA) in aqueous media with high initial water fractions, resulting in hydrogels with high monomer conversion. Both complexes also mediated the synthesis of block copolymers (PHEMA-b-PBA), as confirmed by size exclusion chromatography (SEC), Raman, and 1H NMR analyses. The photoactivation mechanism was further investigated through spectroscopic analyses, providing insights into the redox and reactive processes involved in the photopolymerization reactions.
Shimizo et al. (Tue,) studied this question.