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.