The project aims at (1) obtaining accurate vapour-liquid equilibrium data for industrially important systems containing polymer (mostly biodegradable) + solvent, (2) obtaining results on the conformal behaviour of polymers in solutions at the given thermodynamic conditions and their impact on the phase equilibria, (3) developing a truly molecular-based computer-aided theory as an alternative to empirical and semi-empirical models as e.g., SAFT. The experimental part will focus on improving methodology of getting accurate data on phase equilibria over a wide range of thermodynamic conditions. New simple short-range models will be developed to be used in a perturbation expansion for the Helmholtz free energy. Correctness and accuracy of the theory will be verified by molecular simulations and experimental data. The results acquired can be immediately applied in the design of efficient separation units in chemical and petroleum industry.