Electroconvective dendrites in nematic phases having short range smectic order exhibited by the 4,n-alkoxybenzoic acids

Abstract

Electroconvective (EC) dendrites (parabolic type) in nematic (N) liquid crystals with short range smectic order shown by 4,n-octyloxybenzoic acid (8-OBA) were observed. The driving of the dendrites by lateral d.c. and a.c. electric field parameters in the nematic temperature range was carried out. The dynamics of dendrite growth were studied and analysed by the Ivantsov two-dimensional solution for the diffusion equation. Using various combinations of blocked and unblocked electrodes, we studied dependences between the dimensionless electric field parameter and product of the dendrite parabolic radius and the velocity of the dendrite growth and found that the type of electrode significantly modifies these basic dependences. We attribute this effect possibly to the opposing ion propagation, i.e. gradient of electric field in direction opposite to that of the charge injection. A possible mechanism of EC dendrite growth is suggested. A comparison with thermal dendrites in liquid crystals is presented.