Electronic and Steric Ligand Effects in the Radical Polymerization of Vinyl Acetate Mediated by β-Ketoiminate Complexes of Cobalt(II)

Santhosh Kumar K. S. (1) , Yugang Li (1) , Yves Gnanou (1) , Ulrich Baisch (2) , Yohan Champouret (2) , Rinaldo Poli (2) , Kiyoshi c. d. Robson (3) , W. Stephen Mcneil (3)

1 LCPO - Laboratoire de Chimie des Polymères Organiques
2 LCC - Laboratoire de chimie de coordination
3 UBC Chemistry - Department of Chemistry [Okanagan]

Complexes Co[OC(Ph)CHC(Me)NAr]2 [Ar=Ph, 1; o,o′‐C6H3Me2 (Xyl), 2; p‐C6H4CF3, 3] are tested in the polymerization of vinyl acetate (VAc) initiated by V‐70 (0.8 equiv) at 30 °C. Polymerization occurs without any notable induction time yielding PVAc with relatively low polydispersity, but with higher than expected Mn values, which indicates inefficient trapping processes. The apparent polymerization rate constant varies in the order 2>1>3. Controlled polymer growth is also observed when the polymerization is conducted in the presence of a much higher V‐70/1 ratio, demonstrating that this system can also function as a transfer agent in a degenerative transfer process. Competition between chain growth and catalyzed chain transfer (CCT) is also observed, the latter prevailing at higher temperatures. Comparison of these results with previous reports on bis(β‐diketonato) complexes allows a separate assessment of ligand electronic and steric effects in the ability to control polymerization.

Mots clés: Cobalt; Lewis bases; Ligand effects; Polymerization; Radicals

Domaines: Chimie de coordination; Polymères

Santhosh Kumar K. S., Yugang Li, Yves Gnanou, Ulrich Baisch, Yohan Champouret, et al.. Electronic and Steric Ligand Effects in the Radical Polymerization of Vinyl Acetate Mediated by β-Ketoiminate Complexes of Cobalt(II). Chemistry - An Asian Journal, 2009, 4 (8), pp.1257-1265. ⟨10.1002/asia.200900084⟩. ⟨hal-03184499⟩