Organocatalyzed ATRP meets nature: riboflavin-mediated synthesis of thick polymer brushes under visible light

Abstract

Organocatalyzed atom transfer radical polymerization (O-ATRP) is a powerful technique for precise metal-free synthesis of polymers. Most photocatalysts (PCs) utilized in O-ATRP are synthetically derived; however, naturally occurring compounds are promising candidates for more sustainable and environmentally friendly PCs. In response, riboflavin (RF, vitamin B2) and its derivative (modRF) were tested in surface-initiated O-ATRP (SI-O-ATRP). Tiny quantities of RF and modRF (11 ppm) were sufficient to catalyze the synthesis of thick polymer brushes exhibiting chain-end activity and high grafting density. Ribitol tail modification of RF enhanced control over polymer brush growth and improved the solubility of PC. Three surface-grafted initiators were compared, with the best results observed for 2-bromo-2-phenylacetate-based structures. Near-linear brush growth with SI-O-ATRP time was revealed for optimized conditions. The presented approach is characterized by simple reaction setup, ppm concentrations of naturally derived PC and mild conditions fulfilling prerequisites for metal-free and efficient synthesis of surface-grafted polymers for biomedical and electrical applications.