Dispersity Control via Solvent and Additive Effects in Photoredox‐Mediated Ring‐Opening Metathesis Polymerization

Abstract

ABSTRACT Having a controllable and typically narrow molecular weight distribution is a hallmark of most well‐controlled polymerization techniques, including metal‐mediated ring‐opening metathesis polymerization (ROMP). Control in photoredox‐mediated metal‐free ROMP, on the other hand, has been limited to spatio‐temporal, average molecular weight, and stereochemical control; targeted molecular weight distributions (quantified with dispersity, Đ ) have been elusive. However, we were motivated by the relationship between Đ and elementary reaction rates in reversible deactivation radical polymerizations to explore the solution presented herein. Specifically, we have demonstrated the ability to target specific Đ values, ranging from 1.23 to 1.63, in a logical and operationally simple way: by perturbing the environment of the active chain‐end through solvent and additive effects. We hypothesize that this is due to the consequent effects on the rate of chain‐end deactivation combined with changes in the rate of propagation.