The electroconvection in the nematic liquid crystals with short range smectic C order

Electroconvection (EC) in nematic liquid crystals, which appears before smectic C phase at cooling, was studied. Three detached nematic regions with characteristic ECs were detected under temperature variation. The influence of the change of magnitude and sign of electroconductivity anisotropy, as well as the influence of the nematic director location (both driven by the temperature variation), on EC mechanism and the relevant optical patterns are discussed. The competition between the two possible EC mechanisms: the Carr-Helfrich and the 'isotropic' mechanism, is discussed.