Elucidating Monomer Character of an Alkenyl Boronate through Radical Copolymerization Leads to Copolymer Synthesis beyond the Limitation of Copolymerizability by Side-Chain Replacement.

Isopropenyl boronic acid pinacol ester (IPBpin) was used as a comonomer in radical polymerization with a wide range of common vinyl monomers for elucidation of the monomer character and syntheses of conventionally inaccessible copolymers via the replacement of the boron pendant. The study revealed that the boron-containing monomer is categorized into an electron-rich conjugated monomer, which was well consistent with the results of density functional theory (DFT)-based investigation. One of the thus obtained copolymers, the IPBpin-styrene copolymer, was successfully transformed into an α-methyl vinyl alcohol (MVA)-styrene counterpart via oxidation of the boron pendant. The copolymer cannot be synthesized even with the acetyl-protected monomer instead of IPBpin due to poor copolymerization ability based on the nonconjugated character.