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Know How

Experimental Equipment and Know How

    In this section we give a brief outline of the different methods and apparatuses used in the fields of thermodynamic and rheology of polymer containing mixtures. Particular attention is being paid to the large scale fractionation methods and to the possibilities to study the influences of external pressure on the physico-chemical properties of polymer solutions and polymer blends.

Theoretical Know How

    Abundant experimental data on the composition and chain length dependence of the Flory-Huggins interaction parameter have forced us to establish a fundamentally new approach for the understanding of these findings. The novel Ansatz accounts explicitly for the connectivity of monomeric units in a polymer chain and for the conformational variability of polymer backbone. This methodology is presently extended to polymer with non-linear architecture.

    The main focus of our modeling in the field of polymer-containing mixtures centers on phenomena, which require a sufficient simultaneous understanding of the thermodynamic and of the rheological behavior of such systems. Outstanding examples are: The interrelation between the particular thermodynamic situation and the flow characteristics that follows therefrom and conversely the thermodynamic performance of sheared polymer solutions or polymers blends. In the area of membrane formation such theoretical knowledge is as essential as for the mastering of a phenomenon we denominated thermodynamically induced shear degradation.

    Another theoretical emphasis concerns the influences of external fields on the physico-chemical behavior of liquids. The major work in this area is dealing with shear influences on the miscibility of polymer containing system. We also dispose of theoretical knowledge with regard to the consequences of electric fields on the flow behavior of liquid crystalline substances.

    Out of the different variables of state, pressure constitutes a widely neglected parameter. For this reason we have not only performed numerous thermodynamic and viscometric measurements in this are also paid special attention to the modeling of these results.

    Unlike some biopolymers most of the synthetic macromolecules exhibit a rather broad molecular weight distribution. This feature bears many consequences for their physico-chemical behavior and hampers a clear assignment of experimentally observed phenomena to certain species. On the experimental side we have therefore developed several techniques for large scale fractionation. On the theoretical side we include molecular polydispersity in the modeling of phase diagrams and use polydispersity effects for a better understanding of the experimentally observed interfacial tension between phase separated polymer solutions or polymer blends.


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