Precise Access to Ultrahigh-Molecular-Weight Polymers by Ylide-Functionalized Phosphine-Based Frustrated Lewis Pairs

Lewis pair polymerization (LPP) is an advanced polymerization technique known for its ability to synthesize ultrahigh-molecular-weight (UHMW) polymers under mild conditions with remarkable efficiency and precise control. In this study, a strong electron-donor ylide-functionalized phosphine, (1-(diethylphosphanyl)ethylidene)triphenyl-λ5-phosphane (YFP2), is introduced as a Lewis base (LB). It is combined with a sterically hindered moderately acidic Lewis acid (LA), (4-Me-2,6-tBu2-C6H2O)AliBu2 ((BHT)AliBu2), to prepare a frustrated Lewis pair (FLP) catalyst for the living methacrylates polymerization. The living character of this polymerization has been confirmed through various key observations: successful chain-extension experiments, a linear increase in the number-average molecular weight (Mn) of the polymer corresponding to monomer conversion and the ratio of monomer to initiator, and the development of distinct di- and triblock copolymers using different comonomer addition sequences. Importantly, this FLP catalyst system has successfully synthesized UHMW poly(methyl methacrylate) (PMMA) with Mn values reaching up to 2935 kg/mol and narrow molecular weight distribution (Đ) at room temperature (RT). This achievement establishes a new record for the highest reported Mn for PMMA using a living/controlled LPP system.