Experimental data and theoretical considerations on vapor-liquid and liquid-liquid equilibria of hyperbranched polyglycerol and PVA solutions

Hyperbranched polyglycerol (PG) samples of different molecular weight were synthesized by ring-opening polymerization. Vapor-liquid equilibria (VLE) and liquid-liquid equilibria (LLE) of PG solutions were measured in order to evaluate the potential of hyperbranched polymers for process engineering applications such as extractive distillation and solvent extraction. The VLE experiments focused on the polyglycerol-ethanol-water system, which was contrasted with VLE results for the systems poly(vinyl alcohol) (PVA)-ethanol-water and ethanediol-ethanol-water in order to discuss the impact of polymer branching, functional groups, molecular weight and selective interactions on the phase behavior of the azeotropic ethanol-water mixture. Furthermore, weight activity coefficients and Flory-Huggins parameters for PG in ethanol and in water were determined. For the system acetylated PG-tetrahydrofuran (THF)-water LLE results were reported and distribution coefficients as well as selectivities were discussed. For the analyzed polymer solutions, the extent of inter- and intramolecular hydrogen bond formation is the dominating impact factor on solvent activity and therefore determines partition coefficients and separation factors. Due to their remarkable solution properties, hyperbranched polymers, such as PG can be used for the separation of azeotropic mixtures in the field of process engineering. (C) 2002 Elsevier Science B.V. All rights reserved.