Electroconvection in a homeotropic bent-rod nematic liquid crystal beyond the dielectric inversion frequency

Kumar P, Hiremath US, Yelamaggad CV, Rossberg AG, & Krishnamurthy KS (2008). Electroconvection in a homeotropic bent-rod nematic liquid crystal beyond the dielectric inversion frequency. The Journal of Physical Chemistry B 112 (32): 9753-9760. DOI:10.1021/jp803798g.

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Abstract

We characterize the structural transitions in an initially homeotropic bent-rod nematic liquid crystal excited by ac fields of frequency/well above the dielectric inversion point fi. From the measured principal dielectric constants and electrical conductivities of the compound, the Can-Helfrich conduction regime is anticipated to extend into the sub-megahertz region. Periodic patterned states occur through secondary bifurcations from the Freedericksz distorted state. An anchoring transition between the bend Freedericksz (BF) and degenerate planar (DP) states is detected. The BF state is metastable well above the Freedericksz threshold and gives way to the DP state, which persists in the field-off condition for several hours. Numerous +1 and -1 umbilics form at the onset of BF distortion, the former being largely of the chiral type. They survive in the DP configuration as linear defects, nonsingular in the core. In the BF regime, not far from fi, periodic Williams-like domains form around the umbilics; they drift along the director easy axis right from their onset. With increasing fi, the wave vector of the periodic domains switches from parallel to normal disposition with respect to the c vector. Well above fi, a broadband instability is found.

Item Type: Article
Research Programs: Evolution and Ecology (EEP)
Bibliographic Reference: The Journal of Physical Chemistry B; 112(32):9753-9760 (14 August 2008) (Published online 23 July 2008)
Depositing User: IIASA Import
Date Deposited: 15 Jan 2016 08:40
Last Modified: 26 Feb 2016 12:40
URI: http://pure.iiasa.ac.at/8523

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