A Highly Active Zinc-Based Catalyst System for Lactide Homo- and Copolymerization under Industrially Relevant Conditions

Abstract

Three guanidinium zinc complexes (C1‒C3) with distinct backbones and coordination modes were synthesized and utilized as catalysts for ring-opening polymerization (ROP) testing of racemic lactide (rac-LA) under industrially relevant conditions. In the presence of excess epoxide, even with monomer/catalyst ratios as high as 10⁴, the monomers were successfully polymerized at 150 ^oC or even 180 ^oC, resulting in linear polymer with molecular weights ranging from 8.2 kg/mol to 28.5 kg/mol. The results of the experimentation, computation, and mass spectrometry analysis confirmed that the purposefully designed C3 has the greatest polymerization activity and is capable of producing PLA with a molecular weight of approximately 20.0 kg/mol even in the presence of transesterification. Additionally, the catalytic system also facilitated copolymerization between various cyclic esters, yielding well-defined random copolymers. This research introduces innovative concepts for producing environmentally-friendly catalytic systems that exhibit versatile application potential.