X-ray study of the highly ordered smectic phases of N-pentyl-N'-(p-pentyloxyphenyl)piperazine

The structures of the highly ordered liquid crystalline smectic phases of N-pentyl-N'-(p-pentyloxyphenyl)piperazine are identified using X-ray diffraction methods. For this compound a phase sequence hexagonal smectic B (S_B)-orthofrhombic crystalline smectic H (C_H)-monoclinic crystalline smectic H (C_H) is observed for the first time. The changes in structural symmetry at the phase transitions are discussed.