Conformation-driven reversibility control in ring-opening metathesis polymerization of non-bicyclic cyclooctenes.

Abstract

Reversible ring-opening metathesis polymerization (ROMP) of cyclooctene (COE) derivatives remains a challenge due to their high ring strain energies (RSEs). While previous strategies rely on fused bicyclic systems to reduce RSEs, depolymerization of non-bicyclic COE polymers has proven difficult. Here, we demonstrate efficient reversible ROMP of non-bicyclic COE derivatives by introducing conformational constraints via geminal tert-butyl and hydroxy substituents. These tailored monomers enable depolymerization efficiencies exceeding 90%, achieving near-quantitative monomer recovery under optimized conditions. Experimental and computational analyses reveal that intramolecular OH-π interactions stabilize cyclic conformations in hydroxy-containing monomers, while steric hindrance in the ring-opened form is also critical for efficient depolymerization. This work highlights the interplay between substituent effects, steric control, and molecular conformation in enabling chemical recyclability. It offers an alternative molecular design strategy for developing sustainable materials through reversible polymerization, challenging the conventional reliance on bicyclic systems.