Continuous flow photoinduced phenothiazine derivatives catalyzed atom transfer radical polymerization

Continuous flow photoinduced organocatalyzed atom transfer radical polymerizations (O-ATRP) are investigated by using phenothiazine derivatives as organic photoredox catalysts. A series of phenothiazine derivatives with different substituents are designed and synthesized. The structure-reactivity relationship is examined in both batch and tubular reactor by employing methyl methacrylate (MMA) and ethyl α-bromophenylacetate (EBP) as the monomer and initiator. By transferring the polymerization from the batch reactor to the tubular reactor, the accelerated apparent polymerization constants, better control of molecular weights and narrower molecular weight distributions are achieved. The effect of the inner diameter of the tubular reactor on O-ATRP is explored and it suggests that 1.5 mm and 2.0 mm are the optimized inner diameter based on the consideration of polymerization controllability. By applying this continuous flow photoinduced O-ATRP protocol, poly(methyl methacrylate) (PMMA) and block copolymers are synthesized with varied molecular weights.