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Kent State University

1991

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Articles 1 - 2 of 2

Full-Text Articles in Physics

Determination Of The Liquid-Crystal Surface Elastic-Constant K24, David W. Allender, G. P. Crawford, J. W. Doane Sep 1991

Determination Of The Liquid-Crystal Surface Elastic-Constant K24, David W. Allender, G. P. Crawford, J. W. Doane

Physics Publications

Analysis of the Frank free energy for nematics confined to cylindrical regions indicates that the director pattern is dependent on the surface elastic constant K24 if there is weak normal anchoring and escape along the cylinder axis. Using deuterium nuclear-magnetic-resonance techniques on samples of submicrometer-size cavities in Nuclepore membranes, we report the first measurement of K24.


Finite Molecular Anchoring In The Escaped-Radial Nematic Configuration: A 2-H-Nmr Study, G. P. Crawford, David W. Allender, J. William Doane, M. Vilfan, I. Vilfan Aug 1991

Finite Molecular Anchoring In The Escaped-Radial Nematic Configuration: A 2-H-Nmr Study, G. P. Crawford, David W. Allender, J. William Doane, M. Vilfan, I. Vilfan

Physics Publications

The director-field configuration of a nematic liquid crystal confined to cylindrical cavities of polycarbonate Nuclepore membranes ranging from 0.3 to 0.05-mu-m in radius is determined using deuterium nuclear magnetic resonance (H-2 NMR). Spectral patterns from cavities of radius 0.3-mu-m reveal the escaped-radial configuration with singular point defects, but as the cylinder size is decreased, the elastic energy imposed by the curvature of the confining walls competes with the anchoring energy to tilt the directors away from their preferred perpendicular anchoring direction, preventing the expected transition to the planar-radial configuration. A surface fitting parameter is directly determined by ...