Dresden 2020 – scientific programme

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O: Fachverband Oberflächenphysik

O 97: Wetting and Liquids at Interfaces and Surfaces I (joint session CPP/DY/O)

O 97.7: Talk

Thursday, March 19, 2020, 11:00–11:15, ZEU 255

Tracking nematic flows at microscales using small angle X-ray scattering — •Paul Steffen¹, Eric Stellamanns², Michael Sprung², Fabian Westermeier², and Anupam Sengupta³ — ¹Göttingen — ²Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany — ³Physics of Living Matter, Dept. of Physics and Materials Science, University of Luxembourg, Luxembourg

Liquid crystal microflows play a fundamental role in materials, modern display technologies, and biological systems. However, a quantitative, dynamic and spatially resolved measurement of the director field and surface anchoring remain a significant challenge. Here we present small angle X-ray measurements on stationary flows of 4-Cyano-4-pentylbiphenyl (5CB) in circular Kapton capillaries (under homeotropic and random planar anchoring) at temperatures between 280 and 310 K, and Ericksen numbers ranging from 0 to 200, with a spatial resolution of 1/1000 of the capillary dimension. The angular dependence of the scattering peaks from both periodic length scales was approximated by a double Gaussian fit with four parameters: amplitude, angle, width and background amplitude. The peak angles were found to be in good agreement with the director fields calculated using the Leslie-Ericksen theory. The width and the amplitude of the scattering patterns obtained from the larger length scale are less affected by the temperature than those from the smaller length scale.