External regulation of atom transfer radical polymerization (ATRP) allows for fine tuning of the activity of the copper catalyst, and asserting spatiotemporal control. Temporal control in ATRP was investigated using various external stimuli including zerovalent metals, light irradiation, and chemical redox agents. The activity of the catalyst had a profound effect on the behavior of the system in the presence/absence of stimuli. For example, in more active complexes, due to the very low concentration of L/CuI, a perfect temporal control was obtained. However, less active catalysts resulted in high concentration of L/CuI activator that drove the reaction to higher conversions even in the absence of stimuli. Moreover, a chemical approach was developed to affect the redox properties of the Cu catalyst. Ascorbic acid was used as a reducing agent to (re)generate L/CuI activator. A ferrocenium salt or oxygen was used as oxidizing agents to oxidize L/CuI catalyst, and switch the polymerization off. Therefore, ATRP was successfully switched between on and off states using redox agents, which efficiently modulated the redox state of the catalyst without sacrificing control over the polymerization.

External control in atom transfer radical polymerization

2019 Spring National Meeting

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