Modeling and experimental approaches for the characterization of phase equilibria in polymer solutions

Abstract

The morphology of porous structures prepared via phase separation processes is strongly affected by the thermodynamic properties of the considered system: therefore, a deep characterization of phase equilibria in polymer solutions represents a valid support in the design of membrane production protocols. As the experimental derivation of phase diagram is time and cost consuming, a simple route is proposed, combining both experimental and modeling approaches. The compressible lattice fluid model extended to specific interactions was used to fit experimental cloud point curves for the system PLLA-dioxane-water, which is used for the preparation of porous membranes for various applications. The as derived parameters allow the direct derivation of the complete phase diagram of the system. On the other hand, an apparatus for light transmittance measurements was built and set up for carrying out an experimental detection of cloud point curves. By merging the experimental and modeling approaches, a complete phase diagram of the system can be inferred.