Carbodiimide Ring-Opening Metathesis Polymerization and Depolymerization Using Terminal Iridium Imido Initiators

Carbodiimide ring-opening polymerization (CDI-ROMP) enables chain growth of main-chain poly­(CDI)­s, which in principle could allow for control over the molecular weight, dispersity, and architecture of these polymers and their derivatives. However, thus far, chain transfer has limited this control. Herein, we describe the use of terminal iridium imido initiators, which reduce chain transfer in CDI-ROMP and improve the polymerization control: dispersities of ∼ 1.3 were achieved at complete monomer consumption, with even lower dispersities (1.1–1.2) at conversions below 85%, and the previously observed undershooting of theoretical molecular weight was avoided. Furthermore, we show that these initiators also enable depolymerization of poly­(CDI)­s to monomer with conversions of 50–60% under mild reaction conditions.