Ring‐opening polymerization of substituted ε‐caprolactones with a chiral (salen) AlO<i>i</i>Pr complex

Abstract

Abstract The ring‐opening polymerization (ROP) of ε‐caprolactone (ε‐CL), 4‐methyl‐ε‐caprolactone (4‐MeCL), and 6‐methyl‐ε‐caprolactone (6‐MeCL) with a single‐site chiral initiator, R,R ′‐(salen) aluminum isopropoxide ( R,R ′‐[1]), was investigated. The kinetic data for the ROP of the three monomers at 90° in toluene corresponded to first‐order reactions in the monomer and propagation rate constants of k ε‐CL &gt; k 4‐MeCL ≫ k 6‐MeCL . A notable stereoselectivity with a preference for the R ‐enantiomer was observed in the ROP of 6‐MeCL with R,R ′‐[1], whereas for 4‐MeCL, no stereoselectivity was found. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 429–436, 2007.