Thermotropic liquid crystals from alkali metal dihexadecylphosphates

Lithium, sodium, potassium, rubidium, and caesium dihexadecylphosphates were synthesized. Their thermal stability was checked by thermogravimetry. Their ability to show thermotropic mesomorphic behaviour was investigated using differential scanning calorimetry, polarizing optical microscopy, and X-ray diffraction. All these compounds were found to exhibit a lamellar structure in the crystalline state at room temperature and a columnar structure of hexagonal symmetry in the mesomorphic state at high temperature. The potassium, rubidium, and caesium derivatives were found to exhibit an additional Ia 3 d body-centred cubic structure in the temperature range between the crystal and the columnar phase. Structures and structural parameters are briefly discussed.