Catalytic Synergy Using Al(III) and Group 1 Metals to Accelerate Epoxide and Anhydride Ring-Opening Copolymerizations

Wilfred T. Diment, Georgina L. Gregory, Ryan W. F. Kerr, Andreas Phanopoulos, Antoine Buchard, Charlotte K. Williams

Research output: Contribution to journalArticlepeer-review

Abstract

The controlled synthesis of polyesters via epoxide/anhydride ring-opening copolymerization is a versatile and generally applicable method to make many sustainable polymers, but catalyst activities are limited and the required catalyst loadings are typically high. Here, novel heterodinuclear complexes, featuring Al(III)/M(I) (M = Na, K, Rb, Cs), show exceptional activities for phthalic anhydride and cyclohexene oxide copolymerization (catalyst = Al(III)/K(I), turnover frequency = 1072 h–1, 0.25 mol % catalyst loading vs anhydride, 100 °C). The Al(III)/K(I) catalyst is also tolerant to low loadings, maintaining a good performance at 0.025 mol % catalyst vs anhydride loading and 0.005 mol % vs epoxide. It rapidly polymerizes other epoxide/anhydride combinations yielding various semi-aromatic, rigid, and/or functionalizable polyesters and also shows activity in carbon dioxide/epoxide copolymerizations. The results of structure–activity, X-ray crystallography, polymerization kinetics, and density functional theory investigations support a mechanism with chain growth alternation between the metals. The rate-limiting step is proposed to involve epoxide coordination at Al(III) with K(I) carboxylate attack. Future exploitation of abundant and inexpensive Group 1 metals to deliver synergic polymerization catalysts is recommended.
Original languageEnglish
Pages (from-to)12532-12542
Number of pages11
JournalACS Catalysis
Volume11
Early online date28 Sep 2021
DOIs
Publication statusE-pub ahead of print - 28 Sep 2021

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