Phase behavior

The limits of the complete miscibility of chemically different components and the coexistence of two or more phases belong to our prime interests. Particular attention is being paid to the influences of hydrostatic pressure and shear fields on the phase diagrams of polymer containing systems. A new approach eliminating the deficiencies of the original Flory-Huggins theory comes in very handy in the quantitative description of polymer containing systems.

1. VL equilibria
Direct information on the interaction between polymers and solvents is easy to obtain via vapor pressures. Despite this uncomplicated access an adequate thermodynamic description of polymer solutions and polymer blends is still very topical. One prominent example for discrepancies concerns the theoretically postulated "loss of individuality" of macromolecules in concentrated solutions. By means of improved vapor pressure measurements we could demonstrate that the polymer chains still "know" of their length even at 95 wt% in case of thermodynamically good solvents, in contrast to general believe. Vapor-Liquid equilibria

2. LL equilibria
Knowledge on the demixing behavior of homogenous systems into two liquid phases that is limited to the quiescent state and to atmospheric pressure does sometimes not meet the needs. For this reason we are paying special attention to Pressure influences and study the complex phenomena exhibited by flowing systems, which can only be rationalized by means of joint thermodynamic and rheological considerations. See Liquid-Liquid equilibria dealing with shear influences on the phase behavior of polymer solutions and of polymer blends.

3. LS equilibria
The coexistence of crystalline polymers with their saturated solutions has only recently be come of increasing interest for us. Our investigations primarily concern two question. To which extent it is possible to reach equilibria for such systems and how does shear influence the segregation of polymer crystals from solution. All systems studied so far exhibit shear induced crystallization. Pressure influences