Interfacial Tension of Liquid Crystalline Droplets

The interfacial tension between two low-molar-mass biphenylcarbonitriles that exhibit liquid crystalline phases (4‘-pentyl-4-biphenylcarbonitrile and 4‘-octyl-4-biphenylcarbonitrile) and poly(dimethylsiloxane) was measured as a function of temperature using pendant drop tensiometry enhanced by video-image digitization. Interfacial tensions are increasing functions of temperature, an apparent consequence of homeotropic orientation in the nematic phase and decreasing nematic order with increasing temperature. Nematic order near the interface persists above the bulk nematic−isotropic transition temperature. The interfacial tension in the smectic phase is too low to obtain a stable droplet.