Dresden 2009 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 11: POSTERS Amphiphilic Systems

CPP 11.4: Poster

Tuesday, March 24, 2009, 14:00–16:30, P3

Phase Separation Kinetics under Continuous Cooling: Shape matters — •Doris Vollmer, Mika Kobayashi, Guenter Auernhammer, and Yumino Hayase — MPI for Polymer Research, Mainz

The dynamics of phase separation strongly depends on the thermal protocol, for example, whether phase separation is induced by a single quench from a one-phase to a two-phase region, or slow continuous ramping. In the latter case, qualitatively new features can arise, like oscillations in the turbidity and the apparent heat capacity. Oscillatory phase separation has been observed in several systems, as different as microemulsions, polymer solutions, and even in binary mixtures of olive oil and methanol. Material exchange is achieved through the macroscopic interface between both coexisting phases. To investigate the effect of the interfacial area on the phase transition kinetics we modified the area per unit volume using samples of different geometry, i.e. cylindrical and dog-bone shaped cells. As a model system we studied the phase separation of microemulsions and methanol and hexane under continuous cooling. In the dog-bone shaped cells the oscillation period exceeds those in cylindrical ones at cooling rates of a few K/h. The different dependence on the cooling rate indicates that the phase separation kinetics is either determined by volume dominated nucleation (fast cooling) or interface induced droplet formation (slow cooling).