Pattern formation in phase separating binary mixtures

We experimentally investigate the interplay of thermodynamics with hydrodynamics during phase separation of (quasi-) binary mixtures. Well defined patterns emerge while slowly crossing the cloud point curve. Depending on the material parameters of the experimental system, two distinct scenarios are...

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Bibliographic Details
Published in:Physical chemistry chemical physics : PCCP 2011-08, Vol.13 (29), p.13333-13340
Main Authors: SAM, Ebie M, HAYASE, Yumino, AUERNHAMMER, Günter K, VOLLMER, Doris
Format: Article
Language:English
Subjects:
Binary mixtures
Calorimetry
Chemistry
Cloud point curves
Exact sciences and technology
General and physical chemistry
Heating
Instability
Phase separation
Stability
Turbidity
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Summary:We experimentally investigate the interplay of thermodynamics with hydrodynamics during phase separation of (quasi-) binary mixtures. Well defined patterns emerge while slowly crossing the cloud point curve. Depending on the material parameters of the experimental system, two distinct scenarios are observed. In quasi-binary mixtures of methanol-hexane patterns appear before macroscopic phase separation sets in. In course of time the patterns turn faint while the overall turbidity of the sample increases until the mixtures become completely turbid. We attribute this pattern formation to a latent heat induced instability resembling a Rayleigh-Bénard instability. This is confirmed by calorimetric data and an estimate of its Rayleigh number. Mixtures of C(4)E(1)-water doped with decane phase separate under heating. After passing the cloud point curve these mixtures first become homogenously turbid. While clearing up, pattern formation is observed. We attribute this type of pattern formation to an interfacial tension induced Bénard-Marangoni instability. The occurrence of the two scenarios is supported by the relevant dimensionless numbers.
ISSN:1463-9076
1463-9084
DOI:10.1039/c1cp20889f