Dresden 2011 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 44: Micro- and Nanofluidics I
CPP 44.11: Talk
Thursday, March 17, 2011, 16:45–17:00, ZEU 160
Phase behaviour and rheology of the liquid crystal 8OCB in confinement — •Dominik Gerstner, Simon Gruener, and Patrick Huber — Experimental Physics, Saarland University, Saarbrücken, Germany
To examine the hydrodynamic properties of the liquid crystal 8OCB in nanoscale confinement, we measured the time dependence of its capillary rise into porous Vycor glass. Porous Vycor is a monolithic silica glass, permeated by a random network of pores with a mean diameter of approximately 7 nm. The capillary rise was monitored by the mass uptake m(t) of the system. We observed the typical Lucas-Washburn behaviour for all our measurements, which suggests the validity of bulk hydrodynamics even in such strong confinement. However, the shear viscosity minumum, appearing at the bulk isotropic-nematic transition of 8OCB, is found to be absent. We explain this with the formation of a paranematic phase, i.e. the continuous evolution of molecule alignment due to the ordering effects of the narrow pores. The evolution of the paranematic order can also be seen in 13C neutron magnetic resonance spectroscopy and differential scanning calorimetry measurements on 8OCB in a porous Vycor host.