High pressure studies on partially bilayer and monolayer smectics

Abstract

We have carried out pressure studies on the eighth and ninth members of the homologous series 4-alkoxybenzoyloxy-4'-cyanoazobenzene (nOBCAB). It is found that the pressure behavior of the monolayer smectic A (A1) phase is entirely different from that of the partially bilayer smectic A (A1) phase. The A1-nematic phase boundary is a straight line at all pressures and the range of the Ad phase increases with increasing pressure. On the other hand, the Ad-nematic phase boundary is elliptic in shape and the Ad phase gets bounded. These results emphasize the fact that the pressure behavior of the A phase is strongly related to the extent of overlap of the molecules in the layer.