Original English dissertation · scientific equations reproduced directly from the source PDF.

1 Introduction

Nature comprises a multitude of critical phenomena. Spontaneous symmetry breaking at the origin of the universe and gravitation collapse [1], [2] are spectacular examples. Crit- ical phenomena occur at phase transitions. Theories of phase transitions use methods of catastrophe theory and also of theory of percolation which currently attract considerable attention.

In order to understand critical phenomena, investigations of liquid-liquid phase transi- tions in binary and ternary mixtures are very instructive. Especially the understanding of the phase behavior and the critical phenomena in ternary mixtures, biophysics and mem- brane physics have attracted attention during the last years [3], [4], [5]. The essential and most amazing feature of critical phenomena was the discovery of critical point universal- ity indicating that the microscopic structure of fluids becomes unimportant in the vicinity of the critical point. The understanding of such phenomena is also of great importance for chemistry and chemical engineering in procedures like liquid and solid extraction, drying, absorption, distillation and many other chemical reaction processes, as well as for biology in operations like fermentation, biological filtration and syntheses. Moreover, theories of critical phenomena are substantial for many innovative applications such as supercritical extraction, enhanced oil recovery and supercritical pollution oxidation. The importance of the understanding and application of critical phenomena is demonstrated by the recently (08.28.07) provided studies1 performed in the International Space Station (ISS). The fo- cus of those investigations were the critical phenomena, in particular the critical slowing down of the phase separation near the critical point of binary colloid-polymer mixtures in a micro gravity environment. The aim of such investigations was to develop fundamental physical concepts previously which had so far been masked by gravity effects.

A first qualitative description of the critical behavior of some special systems was al- ready given at the beginning of last century. Examples are liquid/gas transition and the ferro/paramagnetism transition [6]. An essential step towards a deeper understanding of critical behavior was made by Landau’s general theory of phase transitions [7]. Later the theory has been further developed by Onsager, which found the exact solution [8] for

1National Aeronautics and Space Administration (NASA) Expeditions Assigned. Previous studies on crit- ical systems in micro gravity environment have been performed on in 1997 and 1998 on MIR, Source: http://www.nasa.gov.

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