Xu, Y., Lin, L., He, C.-T., Qin, J., Li, Z., Wang, S., Xiao, M., & Meng, Y. (2017). Kinetic and mechanistic investigation for the copolymerization of CO2 and cyclohexene oxide catalyzed by trizinc complexes. Polymer Chemistry, 8(23), 3632–3640. https://doi.org/10.1039/c7py00403f
The authors report using trizinc complexes coordinated with Schiff-base ligands to efficiently copolymerize CO2 and cyclohexene oxide. Via in-situ IR monitoring, they determined the reaction order and activation energies of the polycarbonate and cyclic carbonate products and showed the dependency of the kinetic information on catalyst and cyclohexene oxide concentrations, as well as CO2 pressure.
To obtain the kinetic data, ReactIR tracked the changes in the absorbance of carbonyl stretching vibrations for polycarbonate (1756 cm-1) and cyclic carbonate (1827 cm−1) as a function of time. In separate experiments that varied concentrations of catalyst and cyclohexene, the researchers determined that both catalyst and monomer had linear dependence on the respective concentrations. Furthermore, they determined that the reaction rate order for CO2 pressure was also one for the pressure ranges that were chosen. Additional experiments were performed to establish activation energies for the two products of the reaction using the data from ReactIR measurements. They report that Arrhenius plots reveal that the activation barriers for polycarbonate and cyclic carbonate are 17.8 kJ mol−1 and 83.1 kJ mol−1, respectively. From the information gleaned from these experiments, the authors proposed a detailed reaction mechanism.