Photoiniferter-RAFT polymerization mediated by bis(trithiocarbonate) disulfides

Abstract

Photoiniferter reversible addition fragmentation chain transfer (PI-RAFT) polymerization has gained significant attention; however, scalable methodologies are still lacking. Here, we investigate the use of a RAFT agent precursor, butyltrithiocarbonate disulfide (BisTTC), as an iniferter agent for the polymerization of two model monomers - methyl acrylate (MA) and methyl methacrylate (MMA). Different wavelengths of light were screened to optimise polymerization conditions for both monomers. While BisTTC can photodissociate and initiate polymerization, its activation under visible light is slow and competes with photodegradation. As for methyl acrylate, degradation only occurs during the induction period, so efficient initiation minimises potential side reactions, but the poly(methyl methacrylate)trithiocarbonate end group continues to degrade during polymerization due to the increased lifetime and stability of the propagating radical. Higher energy blue light gives poorer control than green light for the polymerization of MMA, due to increased photodegradation, whilst methyl acrylate polymerization is retarded under green light and requires conditions that strongly favour initiation.