Kinetic Investigation on the Catalytic Ring-Opening (Co)Polymerization of (Macro)Lactones Using Aluminum Salen Catalysts

Abstract

The kinetic behavior of the catalytic ring-opening polymerization (cROP) of a range of macrolactones, including ω-pentadecalaconte (PDL), ambrettolide (Amb), and butylene adipate (BA), and small-ring lactones, including l-lactide (LLA), e-caprolactone (e-CL), e-decalactone (e-DL), and β-butyrolactone (B-BL), using various aluminum salen complexes was investigated. The cROP rates were shown to be first order both in catalyst and in monomer. The activation energies of the polymerization of PDL and LLA in combination with aluminum salen complexes, with and without tert-butyl groups, were determined, showing that the increase in steric hindrance is negatively affecting the polymerization rate of LLA more than of PDL. Interestingly, an increase of the salen diimine bridge from ethylene to 2,2-dimethyl propylene leads to a dramatic increase in rate for the polymerization of small-ring lactones, while it leaves the rate of polymerization of macrolactones practically unchanged. In order to exploit this difference...