Recyclable Bio-Based Photoredox Catalyst in Metal-Free Atom Transfer Radical Polymerization

Two bio-based organic photocatalysts have been prepared for visible light-induced atom transfer radical polymerization (ATRP). Renewable and abundant cellulose grafted with organic dyes is chosen as the photocatalyst to initiate polymerization via the reductive quenching process. Kinetic study and light on/off reaction demonstrate the "living"/controlled nature of the polymerization by light. Block copolymers can be achieved by using the PMMA as a macroinitiator to reinitiate the polymerization of other vinyl monomers, which shows highly preserved Br chain-end functionality in the synthesized polymers. Moreover, the bio-based catalyst can be recycled to catalyze polymerization in a controlled manner for three times. This strategy provides a metal-free recyclable catalytic platform for visible light-induced ATRP.