Vapor-liquid equilibrium data for carbon dioxide + methyl methacrylate are reported at temperatures of 308, 313, 323, and 333 K and pressures in the range of 1-8 MPa. The corresponding measurements of the volumetric expansion of the liquid phase are also presented. A linear relationship is observed between pressure and liquid-phase composition for all of the temperatures considered. The Peng-Robinson equation of state provides a satisfactory correlation of the vapor-liquid equilibrium data. It is also shown that the expansion isotherms coincide when plotted as a function of the liquid-phase composition. The high solubility of carbon dioxide in methyl methacrylate and the significant volumetric expansion of the liquid phase indicate that methyl methacrylate is an appropriate choice for investigating the concept of polymerization in monomers expanded with carbon dioxide.

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Experimental data on the solubility of carbon dioxide in butyl methacrylate are reported at temperatures of 323 and 333 K and pressures in the range of (2 to 10) MPa. Volumetric expansion data for the liquid phase are also reported over the same range of temperature and pressure. The solubility data are correlated with the Peng−Robinson equation of state using two interaction parameters.

The catalytic chain transfer polymerization of CO2-expanded butyl methacrylate and styrene is reported. Experimentally determined values of the chain transfer constant for CO2-expanded butyl methacrylate are presented at 50 and 60 °C and in the range of pressure from 0.1 to 6 MPa, using a cobaloxime complex as the chain transfer catalyst. Similar data are reported for CO2-expanded styrene at 50 °C. The chain transfer constants for both expanded monomers are significantly higher than those obtained in the bulk monomers. It is demonstrated that a linear relationship exists between the chain transfer rate coefficient and the inverse of viscosity. These results provide significant evidence that the rate-determining step in the chain transfer process is diffusion-controlled.

Molecular weight evolution in catalytic chain transfer polymerization of methyl methacrylate expanded with dense CO2 is reported. Experimental molecular weight and polydispersity index data are presented at 50 °C in the range of conversion from 1 to 25%, and at pressures of 5 and 6 MPa. A cobaloxime complex is used as the chain transfer catalyst. Both molecular weight and polydispersity increase in the range of conversion achieved at conditions below the homogeneous expansion limit. Predici simulations suggest that either irreversible catalyst deactivation or cobalt−carbon bond formation, between the catalyst and the propagating radicals, is the most likely mechanism for the increase in molecular weight with conversion. At conditions above the homogeneous expansion limit, a bimodal molecular weight distribution is observed, indicating two zones of polymerization. These conditions produce relatively high molecular weight macromonomers with broad molecular weight distributions.