A Simple Organoaluminum Catalyst for Living/Controlled Lactone Ring-Opening Polymerization: Ultra-High Molecular Weight and Exceptional Alcohol Tolerance

Ring-opening polymerization (ROP) is a powerful and versatile route to biodegradable polyesters, yet its widespread application remains limited by low catalytic activity, complex catalyst synthesis, and high catalyst loadings. Here, we report the “living”/controlled ROP of a broad range of lactones mediated by a simple organoaluminum catalyst, [MeAl(BHT)2] (BHT = 2,6-ditert-butyl-4-methylphenoxy). This catalyst is readily accessible from commercially available trimethylaluminum and BHT without the need for elaborate ligand design or purification. [MeAl(BHT)2] exhibits markedly higher activity than conventional systems such as stannous octoate (Sn(Oct)2). In particular, it achieves a turnover number (TON) of 5700 in the bulk ROP of ε-caprolactone, affording poly(ε-caprolactone) (PCL) with an ultrahigh molecular weight of 448.9 kDa. Moreover, the catalyst shows exceptional tolerance toward alcohol initiators, enabling the synthesis of telechelic polyester polyols with precisely controlled molecular weights and well-defined chain ends at low catalyst loadings.