Selective Polymerization Catalysis from Monomer Mixtures: Using a Commercial Cr‐Salen Catalyst To Access ABA Block Polyesters

ABA triblock polyesters are synthesized using a commercially available chromium salen catalyst, in one pot, from monomer mixtures comprising epoxide, anhydride and lactone. The catalysis is highly selective and applies a single catalyst in two distinct pathways. It occurs first by epoxide/anhydride ring‐opening copolymerization and subsequently by lactone ring‐opening polymerization. It is used to produce various new ABA polyester polyols; these polyols can undergo post‐functionalization and chain‐extension reactions. The ability to use a commercial catalyst and switchable catalysis with monomer mixtures is expected to facilitate future explorations of new classes of block polymers.