Thermodynamic phase equilibrium data relevant to the copolymerization of carbon dioxide (CO 2 ) and cyclohexene oxide (CHO) are reported in this paper. In this system, the need for additional solvents can be prevented by using an excess of the comonomer CO 2 . Therefore, the solubility of poly(cylcohexene carbonate) (PCHC) in CO 2 and the effects of molecular weight and CHO concentration have been experimentally determined using a high-pressure view cell. Since extremely high pressures are required to dissolve PCHC in CO 2 , only low-molecular-weight polymer is soluble within the experimental pressure range. Addition of CHO results in a significant decrease of the cloud-point pressures and a change of the slope of the cloud-point curve in PT-space. The perturbed-chain SAFT equation of state has been successfully used for the correlation and the prediction of the phase behavior in this range. At high temperatures the PC-SAFT model allows for a quantitative description of the phase behavior, whereas at lower temperatures PC-SAFT tends to overestimate the cloud-point pressures.

A novel zinc silsesquioxane complex ([(c-C5H9)7Si7O11(OSiMePh2)]2Zn4Me4 (1)) has been used as a model compound for silica-grafted zinc catalysts in the copolymerization of cyclohexene oxide and CO2. Complex 1 exists as a dimer in the solid state and is moderately active in the copolymerization, and polycyclohexene carbonates have been obtained with a carbonate content of 79−98%. Polymerizations with ZnEt2-treated silica particles resulted in polymer particles with M̄ n and M̄ w values and carbonate contents comparable to those of the polymers obtained with 1. It was further demonstrated that CO2 consumption can be followed online by monitoring the decrease of system pressure during the reaction. CO2 consumption has been interpreted in relation to both polycarbonate and cyclic carbonate formation. These measurements represent the intrinsic kinetics of this reaction, which appear to be directly related to CO2 pressure.