Liquid Crystalline Bicyclo[1.1.1]pentane Derivatives

New liquid crystalline bicyclo[1.1.1]pentane derivatives have been prepared. Nematic and smectic A, B and C phases have been observed. When the bicyclo[1.1.1]pentyl unit is incorporated in a terminal alkyl chain, it acts as a chain stiffener without changing the transition temperature significantly. A bicyclo[1.1.1]pentyl unit placed at the end of the mesogenic moiety acts almost like a ring the liquid crystal transition temperatures are increased significantly compared to analogous compounds without the bicyclo[1.1.1]pentyl unit. A bicyclo[1.1.1]pentyl unit in the centre of the mesogenic moiety only gives rise to low clearing points.