Color Coding Visible-Light Polymerizations to Elucidate Mechanisms

C. Adrian Figg^a, James D. Hickman^a, Georg Scheutz^a, Sivaprakash Shanmugam^b, R. Nicholas Carmean^a, Bryan S. Tucker^a, Cyrille Boyer*^b, and Brent S. Sumerlin*^a

aGeorge & Josephine Butler Polymer Research Laboratory, Center for Macromolecular Science & Engineering, Department of Chemistry, University of Florida, PO Box 117200, Gainesville, FL 32611-7200
bCentre for Advanced Macromolecular Design (CAMD) and Australian Center for NanoMedicine (ACN), School of Chemical Engineering, UNSW Australia, Sydney, NSW 2052, Australia

Controlled radical photopolymerization techniques rely on specific wavelengths to initiate propagation processes through either photolysis, electron-transfer catalysts, or photodegradable initiators. We report mechanistic investigations into aqueous visible-light reversible addition fragmentation chain-transfer (RAFT) polymerizations of acrylamides using Eosin Y as a photoinduced electron-transfer (PET) catalyst. The photoinduced polymerization was found to be dependent upon the irradiation wavelength and reagents, where either reduction or oxidation of the PET catalyst leads to inherently different radical initiation steps. The mechanistic understanding of the role of PET catalyst, wavelength, and reducing agent allowed a redox sensitive monomer to be successfully polymerized under only one PET-RAFT polymerization condition. Therefore, this study provides fundamental insight into visible-light photopolymerizations and allows for a facile means to precise polymeric materials without the need for different catalysts.