Green Light-Controlled\nSwitchable Photoiniferter Polymerization

Isoquinoline-based acid/base switchable\nRAFT agents (SRAs)\nwere\nsynthesized and used as new photoiniferters for visible light-controlled\npolymerization. In contrast to commercially available pyridyl-substituted\nSRAs, isoquinoline-based SRAs absorb green light more strongly, exhibit\nhigher p<i>K</i><sub>a</sub> values, and offer higher rates\nof photolysis. Photoiniferter polymerization was conducted in the\npresence of either blue or green light at 25 °C. A faster rate\nof polymerization was observed for syntheses conducted using isoquinoline-based\nSRAs than using pyridyl-substituted SRAs. Polymers with controlled\nmolecular weights and tunable dispersities were prepared in the presence\nof varying amounts of 4-toluenesulfonic acid. Four pseudoblock poly(methyl\nacrylate)s of tunable dispersity were prepared via chain extension\nexperiments. Well-defined diblock copolymers consisting of a more\nactivated monomer (methyl acrylate) and a less activated monomer (<i>N</i>-vinylpyrrolidone) can be prepared with relatively low\ndispersities.