Formation of a Marangoni convection field in liquid crystal 8CB under temperature gradient.

Abstract

We analyzed the Marangoni convection induced in the liquid crystalline material of 8CB in sandwich cells under temperature gradient. By using fluorescence photo-bleaching method, we measured the flow field near air interface. In the coexistence state of the smectic and the nematic phases, the direction of the observed flow was opposite from that expected from the temperature dependence of surface tension. Moreover, in the coexistence state of the nematic and isotropic phases, the flow field depended on the coating materials of the cell substrates. As for the formation of the flow field, these flow properties indicate the existence of another important physical factor in addition to the surface tension gradient.