<i>Cis</i>-Selective Metathesis to Enhance the Living Character of Ring-Opening Polymerization: An Approach to Sequenced Copolymers

Abstract

The hydrolytic behavior and physical properties of a polymer are directly related to its constituent monomer sequence, yet the scalable and controllable synthesis of sequenced copolymers remains scarcely realized. To address this need, an enhanced version of entropy-driven ring-opening metathesis polymerization (ED-ROMP) has been developed. An unprecedented level of control is obtained by exploiting the kinetic and thermodynamic differences in the metathesis activity of <i>cis</i>- and <i>trans</i>-olefins embedded in large, unstrained macrocycles. First-order rate kinetics were observed, and polymer molecular weights were found to be proportional to catalyst loading. Computational analysis suggests that incorporation of a <i>cis-</i>olefin into the monomer backbone both introduces a thermodynamic driving force and increases the population of metathesis-active conformers. This approach offers a generally applicable method for enhancing living character in ED-ROMP.