Six Atom Elongated Radical Polymerization Enabled by 1,5-Hydrogen Atom Transfer

In conventional radical polymerization, two carbon atoms are elongated in each propagation step, providing polymers with carbon-carbon backbones. Typically, the properties of these polymeric materials are influenced by side-chain functionalities. Increasing main chain complexity can lead to novel properties. Thus, polymer chemists pursued this goal for more than 60 years. In the last few decades, 1,5-hydrogen atom transfer (HAT) under radical conditions has been well explored by organic chemists. We aim to design a series of vinyl monomers that allows the propagating radical to migrate to the side chain via 1,5-HAT before adding to another monomer. By this distinctive propagation pathway, six atoms and diverse functional groups can be introduced within the polymer backbone. Herein, we report our investigation on radical polymerization of 2-dimethylvinylsilylbenzaldehyde (DMVSB) and its derivatives. The generated alpha-silyl radicals can migrate to aldehydes with up to 100% efficiency via 1,5-HAT, embedding silanes and ketones into the polymer chain. Additionally, DMVSB can be copolymerized with tert-butyl acrylate and maleic anhydride entirely by the 1,5-HAT radical relay pathway. Due to multidegradable functionalities within the backbone, the homo- and copolymers can be degraded under different conditions.