From the discovery of the partially bilayer smectic A phase to blue phases in polar liquid crystals

The significance of Gray’s cyanobiphenyls in the discovery of the partially bilayer smectic A phase (SmAd) and in the formulation of mixtures exhibiting the blue phase is described. The properties of the SmAd phase and its relationships to molecular structures are reviewed. Induced phenomena such as the transformation of nematics into smectics, SmAd or SmA1, as well as the opposite transformation of smectics into nematics are described and discussed.