Predicting solubilities in polymer systems using COSMO-RS

COSMO-RS is an advanced method for calculating the thermodynamic properties of chemical compounds and their mixtures. Unlike other approaches which use group contribution or limited to chemical structures for which empirical data exists, COSMO-RS is based on quantum mechanical calculations. By a unique combination of electron Density Functional Theory (DFT) with continuum solvation theory and efficient statistical thermodynamics procedures, COSMO-RS extends the broad applicability of DFT to thermophysical property predictions. Thus COSMO-RS is able to predict the free energies of almost any chemical compound in almost any solvent and mixture. A number of applications of COSMO-RS to VLE and LLE of small molecules have already been reported. The ability to predict the solubilities of gases, plasticizers and other additives in polymers is of practical importance. Since the permeability of polymer films depends on the solubility of a fluid compound in the polymer, this capability is very useful in the development of selective membranes. Similarly, predicting the solubilities of polymers in a given solvent has many industrial applications. Using COSMO-RS to predict polymer solution properties requires special treatment. In this presentation, the procedure for calculating solubilities in systems containing polymers and polymer blends will be described, the limitations of the approach will be pointed out, and then comparisons between experimental results and COSMO predictions will be given.