Berlin 2012 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 16: Poster: Colloids and Complex Liquids

CPP 16.16: Poster

Dienstag, 27. März 2012, 18:15–20:45, Poster A

Spontaneous emulsification of thermotropic liquid crystals in aqueous surfactant solutions — •Karthik Peddireddy, Pramoda Kumar, Shashi Thutupalli, Stephan Herminghaus, and Christian Bahr — Max-Planck-Institute for Dynamics and Self-Organization, Göttingen, Germany

Thermotropic liquid crystals (LCs) are organic liquids which are usually not miscible with aqueous phases. The presence of surfactants enables the generation of LC-in-water and water-in-LC emulsions, provided that sufficient mechanical energy is added to the system; in that respect the LC/water systems behave just as numerous non-LC oil/water systems.

We have recently observed that some common LC compounds (such as, e. g., the 4-n-alkyl-4^′-cyanobiphenyls) can undergo a spontaneous emulsification process, running without addition of mechanical energy, when brought in contact with aqueous surfactant solutions. The details of the process and the observed transient structures depend on the type of the LC phase: For nematic phases we observe the formation of aqueous droplets in the nematic bulk phase as well as nematic droplets in the aqueous bulk phase. For smectic phases, transient structures appear which resemble the myelin figures formed by lyotropic lamellar phases in contact with water. Polarizing microscopy and fluorescence microscopy studies are conducted in order to elucidate the mechanism of this possibly new type of spontaneous emulsification.