Investigation into the mechanism of photo-mediated RAFT polymerization involving the reversible photolysis of the chain-transfer agent†
A new dithiocarbamate with a N-carbazole Z group is synthesized and investigated as a chain-transfer agent (CTA) in a photo-mediated RAFT polymerization mechanism involving its partial and reversible photolysis. Excellent control of the polymerization of butyl acrylate is observed using LEDs as light sources emitting either in the blue or green wavelength domain. As a photo-mediated reversible deactivation radical polymerization (RDRP) mechanism, the polymerization can be easily stopped or reinitiated by simply switching off or on the light source. This behavior is exploited for subsequent chain-extensions of macroCTAs. A simple kinetic modeling is then proposed, which can support the trends observed experimentally, such as the effects of light intensity and wavelength on the apparent polymerization rate. The developed equation suggests also ways to improve the control of the polymerization by playing on the photolysis pseudo-equilibrium, while underlying the importance of the quantum yield of photodissociation of the CTA.