Metal-Catalyzed Switching Degradation of Vinyl Polymers via Introduction of an "In-Chain" Carbon-Halogen Bond as the Trigger.

In this work, we achieved switching degradation of vinyl polymers made of a carbon-carbon bonded backbone. Crucial in this strategy was a small feed of methyl α-chloroacrylate (MCA) as the comonomer in radical polymerization of methyl methacrylate (MMA) so that the carbon-halogen bonds were introduced as the triggers for degradation. The "in-chain" trigger was activated by a one-electron redox metal catalyst as the chemical stimulus to generate the carbon-centered radical species, and subsequently, the neighboring carbon-carbon bond was cleaved via an electron transfer of the radical species giving the terminal olefin. Particularly, an iron complex (FeCl 2 ) in conjunction with tributylamine ( n -Bu 3 N) was effective as the chemical stimulus to allow the switching degradation, where the molecular weight was gradually decreased over time. The switching feature was confirmed by some control experiments.