Green Light-Controlled Switchable Photoiniferter Polymerization

Isoquinoline-based acid/base switchable RAFT agents (SRAs) were synthesized and used as new photoiniferters for visible light-controlled polymerization. In contrast to commercially available pyridyl-substituted SRAs, isoquinoline-based SRAs absorb green light more strongly, exhibit higher pKa values, and offer higher rates of photolysis. Photoiniferter polymerization was conducted in the presence of either blue or green light at 25 °C. A faster rate of polymerization was observed for syntheses conducted using isoquinoline-based SRAs than using pyridyl-substituted SRAs. Polymers with controlled molecular weights and tunable dispersities were prepared in the presence of varying amounts of 4-toluenesulfonic acid. Four pseudoblock poly(methyl acrylate)s of tunable dispersity were prepared via chain extension experiments. Well-defined diblock copolymers consisting of a more activated monomer (methyl acrylate) and a less activated monomer (N-vinylpyrrolidone) can be prepared with relatively low dispersities.