Thermodynamics and phase equilibria of carbon dioxide/polymer systems

A theoretical approach, the SAFT (Statistical Associating Fluid Theory) equation of state, is adapted and extended to understand the thermodynamics and phase equilibria of systems containing carbon dioxide (CO 2), CO2-philic and CO2-phobic compounds, including both small molecules (such as n-alkanes and n-perfluoroalkanes) and macromolecules (homopolymers, polymer blends and copolymers), to provide rapid reliable predictions for a wide range of systems of interest.; Most prior research has concentrated on developing SAFT equations suitable for phase equilibrium calculations (vapor-liquid and liquid-liquid). In the present work we demonstrate that the SAFT equations are particularly useful not only in pressure-temperature-volume-composition phase equilibrium problems but, also for more difficult aspects of the behavior of mixtures such as derivative properties (e.g., Joule-Thomson inversion curves) and formation of aggregates. To accomplish this goal, we studied the strengths and limitations that different thermodynamic models present not only for pure CO2, but also for its mixtures with small molecules and macromolecules. The research is divided in three major areas: (a) a fundamental investigation of the thermophysical properties of pure carbon dioxide, using predictions from both molecular simulations and equations of state; (b) a detailed study of the phase equilibria of binary and ternary mixtures of CO2, n-perfluoroalkanes and n-alkanes as a representation of small CO2-philic and partially CO2-phobic compounds; and (c) a study of phase equilibria in binary and ternary mixtures of CO2, CO2-philic and CO2-phobic polymers. The ability of the SAFT approach to perform such predictions relies on its more rigorous foundation, since it is practically the only approach that has been able to describe both small molecules and macromolecules.