Liquid crystals under compression and tension

We report measurements of the temperature dependences of the birefringence of a number of nematogens under high pressures. In a compound whose molecules have large longitudinal dipole moments, we detect a nematic to nematic transition when the order parameter is sufficiently high. We also describe a technique of subjecting aligned liquid crystal droplets to large negative pressures and measuring the temperature dependence of birefringence under isochoric conditions. The temperature range of the partial bilayer smectic Ad phase gets shrunk at elevated pressures but gets enlarged under tension.