The catalytic chemistry of Lewis pairs has attracted an explosive level of interest since the “frustrated Lewis pairs” (FLPs) concept was uncovered through the seminal works of Stephan and Erker. Recently, FLPs has been shown to efficiently promote the polymerization of lactones and polar vinyl monomer. Lewis pairs are highly active for polymerization of polar vinyl monomer, affording typically high molecular weight polymers with relatively narrow molecular weight distributions. Especially effective systems are the Lewis pairs (LPs) consisting of the LA Al(C₆F₅)₃ (or B(C₆F₅)₃) and strong LBs, such as phosphines and N-heterocyclic olefins, N-heterocyclic carbenes and phosphazene superbases, for polymerization of methacrylates, acrylamides, 2-vinyl pyridine, 2-isopropenyl-2-oxazoline, α-methylene-γ-butyrolactones, diethyl vinylphosphonate, as well as renewable dissymmetric divinyl polar monomers. Chain initiation involves cooperative addition of LPs to the monomer to generate zwitterionic active species, chain propagation proceeds via a bimetallic, activated-monomer addition mechanism, and chain chain-termination via two pathways: one that proceeds via intramolecular backbiting cyclization involving nucleophilic attack of the activated antepenultimate ester group of the growing chain by the C-ester enolate active chain end to generate a cyclic β-ketoester chain end, and the other that proceeds via intramolecular backbiting cyclization involving nucleophilic attack of the activated adjacent ester group of the growing chain by the O-ester enolate active chain end to generate a δ-valerolactone chain end. Lactones are also polymerize to produce linear or cyclic polymer using FLPs consisting of the LB amine and LAs, such as Zn(C₆F₅)₂, alkylaluminum, and indium chloride.

Contents
1 Introduction
2 Thedevelop of Lewis acid and Lewis base polymerization systems
3 The kind of FLP polymerization systems
4 The polymerizationmechanism of FLP polymerization systems
4.1 Chain initiation and chain propagation
4.2 Chain termination
5 Conclusion and outlook