Sign reversal in the dielectric anisotropy as functions of temperature and frequency in the nematic phase of a bent-core mesogen | Zendy

Yun Hee Jang | Zendy; В. П. Панов | Zendy; C. Keith | Zendy; Carsten Tschierske | Zendy; J. K. Vij | Zendy

Open Access

Sign reversal in the dielectric anisotropy as functions of temperature and frequency in the nematic phase of a bent-core mesogen

Author(s) -

Yun Hee Jang,

В. П. Панов,

C. Keith,

Carsten Tschierske,

J. K. Vij

Publication year - 2010

Publication title -

applied physics letters

Language(s) - English

Resource type - Journals

SCImago Journal Rank - 1.182

H-Index - 442

eISSN - 1077-3118

pISSN - 0003-6951

DOI - 10.1063/1.3498674

Subject(s) - liquid crystal , condensed matter physics , anisotropy , materials science , mesogen , phase (matter) , dielectric , bent molecular geometry , core (optical fiber) , spectroscopy , nuclear magnetic resonance , optics , chemistry , physics , organic chemistry , liquid crystalline , optoelectronics , quantum mechanics , composite material

The sign reversal in the dielectric anisotropy (ϵ∥′−ϵ⊥′) from positive to negative is observed for 4-cyanoresorcinol bisbenzoate system with temperature and frequency in the nematic phase of a bent-core system as the temperature is reduced. This cross-over in dielectric anisotropy is such that at temperatures much below the cross-over temperature, the negative anisotropy is found to be independent of frequency. The experimental observation is supported by results from optical transmittance spectroscopy. This observation is suggested to arise from the following two sources: the presence of cybotactic clusters found by x-ray scattering in the same compound in its nematic phase and conformers that may change the bent core angle at a certain temperature as observed by nuclear magnetic resonance in a similar compound.

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