Surface tension of a liquid crystal in the vicinity of the transition temperature
Author
Al-Siyaby, Amal Salim Ali
English abstract
The behavior of the surface tension of 5CB near the nematic-isotropic
transition temperature has been investigated using two different technique pendant drop and the sessile drop. We have shown that the surface tension behaves normally away from the transition temperature; it decreases as the temperature increase. This is because the molecules on the surface of the liquid are less ordered than the one on the bulk. On both techniques, at a temperature 1.5 degree below the transition the surface tension canny start to increase by increasing the temperature and continues the same behavior up to one degree above the transition on the pendant drop technique and 1.5 degree on the sessile droptechnique. The surface tension shows a positive discontinuity on the
pendant drop technique and a negative discontinuity on the sessile drop technique.
Optical observations of the surface of the 5CB drop below the transition
temperature were also done. It shows that the surface of the drop close to the
transition is not uniform; there are some fluctuating areas at the surface between the nematic and the isotropic phases. These fluctuations and abnormality of the surface tension behavior happens between two points that corresponds to the spinodal points. This work gives explanation to the surface tension behavior and the optical observations of the drop surface.
