Rare-Earth Aryloxide/Ylide-Functionalized Phosphine Frustrated Lewis Pairs for the Polymerization of 4-Vinylpyridine and Its Derivatives

This work reports the efficient polymerization of 4-vinylpyridine (4VP) using Lewis pairs composed of homoleptic rare-earth (RE) aryloxides and ylide-functionalized phosphines (YPhos). The resultant P4VP was readily quaternized by the addition of 1-bromododecane. Polymerization of 4VP derivatives (2-methoxy-4-vinylpyridine, 4-vinylquinoline, and 2,6-dimethyl-4-vinylpyridine) also occurred under identical reaction conditions. The RE/YPhos Lewis pair polymerization system effectively copolymerized 4VP with methyl methacrylate, which resulted in copolymers with gradient architectures and narrow molecular weight distributions. A combined experimental and computational study provided critical insights into the polymerization mechanism. Density functional theory calculations also revealed that the use of YPhos as a Lewis base greatly facilitated both the initiation and subsequent monomer insertion in comparison with PEt3.