External and Reversible CO2 Regulation of Ring-Opening Polymerizations Based on a Primary Alcohol Propagating Species

We report the use of an organic catalyst system capable of switching between active and dormant propagating states during the ROP of cyclic monomers. While the ROP of both ε-caprolactone and trimethylene carbonate proceeds under nitrogen, the simple addition of CO 2 results in a dormant “off” state. Cycling between atmospheres provides the ability to regulate the molecular weights of the resulting polymers without appreciable loss of catalytic activity for several “on/off” cycles.