Photocatalyzed Hydrogen Atom Transfer Degradation of Vinyl Polymers: Cleavage of a Backbone C−C Bond Triggered by Radical Activation of a C−H Bond in a Pendant

Abstract

AbstractIn this work, we achieved a triggering degradation of polymers composed of carbon‐carbon (C−C) bonded backbone without relying on introduction of labile heteroatom‐based bond. The crucial point for the achievement is using vinyl ether (VE) as a comonomer in radical copolymerization of (meth)acrylate for introduction of the carbon‐hydrogen (C−H) bonds active for photocatalyzed hydrogen atom transfer (HAT) as triggers in the pendant. Interestingly, methyl methacrylate (MMA)‐n‐butyl vinyl ether (NBVE) copolymer underwent degradation in acetonitrile in the presence of benzophenone (Ph2CO) under UV irradiation at 80 °C. The degradation did not take place, when any one of UV, Ph2CO, heat, and NBVE unit was removed or HAT‐active solvent such as toluene and 1,4‐dioxane was used. These control experiments strongly supported the HAT‐triggering degradation. Furthermore, the degradation behaviors of the copolymers with other vinyl ethers such as tert‐butyl vinyl ether and methyl isopropenyl ether indicated that the C−H bond neighboring to oxygen on the pendant is mainly responsible for the trigger leading to degradation. The HAT‐triggering degradation was also demonstrated even with the acrylate‐based copolymer.