Boron-Based Lewis Pairs Catalyzed Living, Regioselective, and Topology-Controlled Polymerization of (E, E)-Alkyl Sorbates.

It remains as a great challenge to realize living and controlled polymerization of renewable monomers by the boron-based Lewis pairs. Here, strong nucleophilic N-heterocyclic olefins (NHOs) or N-heterocyclic carbenes (NHCs) as Lewis bases, and boron-based compounds as Lewis acids, are employed to construct LPs for polymerization of alkyl sorbates, including (E, E)-methyl sorbate and (E, E)-ethyl sorbate. Systematic investigation reveals that the combinations of B(C 6 F 5 ) 3  with appropriate acidity and steric hindrance, and strong nucleophilic NHOs promote living and controlled polymerization of alkyl sorbates in 100% 1,4-addition manner, furnishing polymers with predicted molecular weight (M w up to 56.6 kg mol -1 ) and narrow molecular weight distribution (Đ as low as 1.12). Furthermore, topology analysis shows that NHC1/B(C 6 F 5 ) 3  LP produce PMS possessing cyclic structure.