  Polarizing optical microscopy and differential scanning calorimetry are used
to determine the phase sequence of three liquid crystalline
4-pentylphenyl-4'-n-alkyloxythiobenzoates with n = 9, 10, 11. The X-ray
diffraction method is applied for structural characterization of the liquid
crystalline phases. The smectic layer spacing, tilt angle, average distance
between the long axes of molecules and correlation length of the short-range
order are determined as a function of temperature. For the crystal-like smectic
phases with hexagonal or herring-bone packing, the unit cell parameters are
obtained. The presence of the tilted hexagonal phase for n = 10, 11 and tilted
herring-bone phase for n = 9, 10 is indicated, although the direction of the
tilt cannot be determined.
