Norbornadiene Chain-End Functional Polymers as Stable, Readily Available Precursors to Cyclopentadiene Derivatives

A novel method for facile postpolymerization functionalization of synthetic polymers using terminal norbornadiene (NBD) building blocks is presented. Incorporation of the NBD functionality streamlines the synthesis of a wide array of block polymers utilizing multistep click chemistry strategies. Previously, the use of NBD-functionalized initiators produced polymers that underwent a cascade of Diels–Alder (DA) reactions to unveil a reactive cyclopentadiene (Cp) chain end. When coupled with a maleimide-bearing counterpart, a highly efficient DA cycloaddition with the terminal Cp can occur. To extend this concept to a range of polyacrylates and commercially available poly­(ethylene glycol) systems, we developed a novel NBD acid building block for postpolymerization functionalization. Employing this process, we have demonstrated straightforward access to a library of block polymers that leverage this NBD click platform.