NOVEL THERMOTROPIC LIQUID-CRYSTALS WITHOUT A RIGID CORE FORMED BY AMPHIPHILES HAVING PHOSPHONIUM IONS

Thermotropic liquid-crystalline behavior of phosphonium salts, which a re structurally simple amphiphiles with positively-charged phosphorus atoms and without rigid cores, was evaluated by differential scanning calorimetry, polarizing optical microscopy, and X-ray diffractometry. The phosphonium salts were found to show a smectic A (S-A) phase in wh ich a homeotropic structure was formed spontaneously. It is significan t that the phosphonium salts possess an advantageous feature as thermo tropic liquid crystals and show a stable liquid-crystalline phase and a simple phase transition behavior in comparison with commonly availab le ammonium analogs. For example, dimethylditetradecylphosphonium chlo ride showed the highest S-A to isotropic (I) phase transition temperat ure (T-SI, 187 degrees C) and the S-A phase in the widest temperature range (119 degrees C on heating) among the cationic amphiphiles examin ed in the present study, while dimethylditetradecylammonium chloride w ith the same structure except the cationic part showed the lowest T-SI (70 degrees C) and the narrowest liquid-crystalline temperature range (22 degrees C on heating).