Experimental Observation of Sessile Water Droplets in Nematic-Water Mixture Cells

Abstract

An experimental phenomenon - formation of small (3–5 microns) sessile water droplets attached to the glass plates of the liquid crystal cells with either 96.42 wt% Merck 997–3.58 wt% water mixture or 96.80 wt% Liquid crystal 440–3.20 wt% water mixture after the heating-cooling cycle through the clearing point has been observed. The effect can be enhanced by use of either lecithin dissolved in the liquid crystal, or polyvinyl alcohol (PVA) dissolved in the water. In these cases the number of the sessile water droplets increases and their radius decreases. The sessile water droplets disturb the initial homeotropic orientation of the nematic Merck 997-water mixtures and many cross-like or more complex birefringent patterns are observed. When the orientation of the liquid crystal is planar at both surfaces (Liquid crystal 440-water mixture) one observes the formation of Schlierentextures. This effect is explained by phase separation of that part of the water which has been dissolved in the liquid crystalline matrix. The effect of the phase separation of the water is accompanied by increase of the clearing point which can reach that of the pure liquid crystal.

Key Words:

• nematic-water
• mixture
• sessile water droplets
• phase separation