The common denominator of our research consists in the kind of systems we are studying with respect to their physico-chemical behavior. In almost all cases these are fluid mixtures, containing polymers and consisting of at least two components. Our experimental and theoretical work focuses on the thermodynamic and on the rheological behavior of polymer solutions and polymer blends. In the thermodynamic field the elimination of the well-known deficiencies of the Flory-Huggins equation has become one of our major research areas.
The overlap region of thermodynamics and rheology is of particular interest to us. The questions we are studying in this context are for instance: How is the phase separation of flowing mixtures changed as compared to the quiescent state and what are the influences of the rheological parameters of the system? Or vice versa: How do certain thermodynamic conditions manipulate the rheological properties of a mixture? Research in this area is also very helpful in our investigations in the field of polymer membranes.
We are paying special attention to the thermodynamic and rheological effects of hydrostatic pressure, since this variable is often neglected, despite its practical and theoretical significance. In this context we are also investigating polymer solutions in compressed gases.
A further area that deserves explicit mentioning are interfacial phenomena. Here we are examining the interfacial tension between coexisting liquid phases and possibilities for their reduction by small amounts of additives. Research in this filed is of particular interest for the processing of polymer blends and for instance required in the context of the rheology of two phase systems we are also studying.
Last, but not least, it appears worthwhile to mention that we have developed two large scale fractionation techniques: CPF (Continuous Polymer Fractionation), a special kind of continuous counter-current extraction, that allows the separation of macromolecules according to their solubility (normally controlled by the chain length) on an industrial scale and CSF (Continuous Spin Fractionation) that eliminates some drawbacks of CPF by using spinning nozzles for a fine subdivision of the feed phase. So far this method has been successfully employed to approximately 25 chemically different polymers and this number is steadily increasing.