Simulation and theory of equilibrium properties in complex macromolecular fluids

Phase equilibria in complex polymeric fluids have been studied by resorting to both molecular simulation techniques and mean-field theories. The results obtained by such methods have provided useful insights regarding the entropic mechanisms that give rise to different phase transitions in polymeric systems. The systems and phenomena investigated in this work are relevant to processes of significant technological importance, such as blending of polymers, colloidal stabilization, synthesis of microstructured materials, purification and delivery of chemicals, etc.; Novel Monte Carlo techniques have been developed to surmount the difficulties associated with simulation of free energies and phase transitions in macromolecular systems, and to permit simulation of molecules with sizes at least one order of magnitude larger than those previously tractable. New methods have also been devised to simulate phase transitions of semiflexible polymers of arbitrary topological complexity; these methods have permitted the investigation of the structure, compressibility, and swelling of crosslinked polymers and gels.; Simulations have been conducted to determine the effect of molecular shape and other entropic parameters on polymer solubility, vapor-liquid and liquid-liquid equilibria of polymers, equilibrium swelling of gels, and isotropic-nematic phase transitions in liquid crystalline systems. Different scaling regimes have been identified for the average expansion of an infinitely dilute polymer molecule in an athermal solvent, as a function of chain length. The scaling of critical properties with chain length has been determined for fluid-fluid equilibria in model polymeric systems. The existence of entropy-driven separations in athermal gels and liquid crystals has been demonstrated and characterized.; A mean field theory has been formulated to describe the thermodynamic properties of polymers of arbitrary intramolecular connectivity; this approach has been shown to provide good agreement with simulation data for athermal chain molecules, networks, and attractive homopolymers.