Uncovering and understanding “transesterification triggers” in aliphatic polyester synthesis with bis-Zn catalysts

Abstract

On paper, the generation of block copolymers through sequential copolymerisation of two lactones should be straightforward when using a living polymerisation. In practice, this is often not the case, and random copolymer architectures can occur due to transesterification processes. The ability to predict whether certain lactone monomer combinations will deliver block or random copolymers is currently missing. Through a systematic study of monomer features, this work uncovers the impact of monomer substituents, ester functional group density, Lewis basicity, and chelation potential, to identify the key factors that favour or disfavour transesterification. This work uncovers a general trend where the most Lewis basic monomers promote transesterification. By demonstrating that the effective Lewis basicity can be assigned using 19F NMR probe studies, and intrinsic Lewis basicity can be assigned via 13C NMR and FT-IR analysis, this work generates understanding, and in some cases enables prediction, of whether transesterification will occur or not.

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