Quaternary onium modified SalenCoXY catalysts for alternating copolymerization of CO2 and propylene oxide: A kinetic study

• A competition mechanism between polymerization and cycloaddition is proposed.
• A bimetallic mechanism containing SalenCo cations is suggested for polymerization.
• A second-order reaction of catalyst is illustrated according to kinetic data.

Quaternary onium modulated SalenCoXY (X = Cl, Br, NO3; Y = phenoxy, benzene-1,4-bisoxy, benzene-1,3,5-trisoxy) catalysts incorporating the N,N′-bis(salicylidene)ethylene diaminato(Salen) ligand and quaternary onium units were designed, synthesized and applied to the copolymerization of CO2 and propylene oxide. The impact factors of the axial anion X, the counter anion Y and the property of quaternary onium group evidently affected PPC selectivity and degree of polymerization. Detailed kinetic investigations and mechanisms of the cycloaddition and copolymerization were documented and discussed. A second order of catalyst was restrainedly proposed for polymerization.

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