The influence of reagent concentration on the kinetics of carbon dioxide-propylene oxide copolymerization in the presence of a cobalt complex

Abstract

The effect of the concentrations of propylene oxide and the catalyst (salen)CoDNP/[PPN]Cl ((salen)CoDNP: [PPN]Cl = 1: 1, mol/mol) on the kinetics of the copolymerization of CO2 and propylene oxide at 0.5 MPa and 20°C has been studied. The reaction proceeds at a constant rate after an induction period, and the value of this period varies with the reagent concentrations. The steady-state reaction rate increases linearly with the propylene oxide concentration in the range 5.0–14.3 mol/L. At high catalyst concentrations, such as (5.2–7.3) × 10−3 mol/L, the reaction rate is first order in the catalyst; at concentrations below 5 × 10−3 mol/L, the reaction rate is second order in the catalyst. Molecular mass increases in proportion to the propylene oxide conversion, that is consistent with a living polymerization process. A regioregular copolymer with 96% head-to-tail (HT) connectivity of propylene oxide has been obtained.