THE THERMOTROPIC LIQUID-CRYSTALS FORMED BY ANHYDROUS SODIUM RICINOLEATE

The polymorphism of sodium ricinoleate has been examined using differe ntial scanning calorimetry, optical microscopy and low angle X-ray dif fraction. There are three low temperature phases, separated by small t ransition enthalpies, where the molecules are packed in layers with li ttle molecular disorder. At high temperatures (> 160-degrees-C), two s emi-molten mesophases are formed. Both have distinct optical textures under polarizing microscopy, that of the highest temperature phase bei ng the typical fan pattern of a hexagonal phase. X-ray diffraction sho ws that this phase is comprised of hexagonally packed oblate spheroids arranged in layers according to an ABAB type pattern. It has not been reported previously for surfactants. The head groups from the cores o f the spheroids with molten alkyl chains filling the remaining space. In the lower temperature mesophase, the head groups pack into rods joi ned in fours to give layers of a tetragonal array. The layers stack to give a body centered tetragonal structure. Again, the head groups for m the rod cores, while alkyl chains fill the remaining space.