Polymerization Chemistry of Vinylboronic Acid Derivatives: Boron-Based Monomer Design and Polymer Reaction through Side-Chain Replacement

Abstract

In chain-growth polymerization, (co)polymerization abilities of monomers are heavily dependent on the element or functional group attaching to vinyl moiety, resulting in the limitation of accessible polymers. The replacement of the element on the polymer main chain could lead to access new class of polymers with overcoming the synthetic limitations. Herein, we describe the usability of alkenylboronic acid derivatives as the monomers for radical polymerization and post-polymerization transformation through carbon-boron bond-cleaving side-chain replacement. The key for radical polymerization ability of alkenyl boronate was vacant p-orbital of boron for moderate stabilization of chain growth radical. The alkenyl boronate monomers are usable for copolymerization with common monomers as well as for RAFT polymerization. The C-B bond transformation allows syntheses of conventionally inaccessible polymers, such as poly(α-methyl vinyl alcohol), poly(α-methyl vinyl amine), styrene-vinyl alcohol copolymer, and ethylene-acrylate copolymer. Boron on the polymer main chain was also used as the trigger for stimuli-responsive backbone degradation of methacrylate polymer through C-B bond homolysis and β-scission. Thus, alkenyl boronate monomers have an impact on not only breakthrough of the limitation in polymer synthesis but also development of novel polymer functions.