Simplified surface-initiated iron-based photoinduced ATRP : a facile route for polymer brush synthesis in microliter volumes

This report concerns the development of a surface-initiated iron-based photoinduced ATRP (SI-photo-Fe-ATRP) for efficient synthesis of polymer brushes under mild conditions utilizing microliter volumes of reagents. We proposed a simplified reaction setup composed of only initiator decorated substrate, monomer, solvent and FeBr3 which does not require the use of any additional ligands such as amines like in copper-based SI-photoATRP or halide anions as in previous report concerning SI-photo-Fe-ATRP. This was possible due to the use of solvents that play a dual role, i.e. creating a reaction medium and complexing iron salts. SI-photo-Fe-ATRP was proven to be effective in the synthesis of thick poly(benzyl methacrylate) brushes in a reasonable timeframe under harmless visible light. As a result, the developed methodology complies with the requirements of green chemistry in many aspects e.g. by reducing complexity, minimizing waste production, using less harmful biocompatible catalyst systems and ensuring mild synthetic conditions. SI-photo-Fe-ATRP was investigated in terms of selecting optimal: monomer to catalyst ratio, surface-grafted initiator structure, light intensity, and solvent type. This work also addresses the reproducibility of polymerization and provides tips for dealing with this issue. It was shown that SI-photo-Fe-ATRP can be adopted to produce polymer brushes outdoors under sunlight and without the need to use restrictive synthetic conditions.