Structural and calorimetric investigations on nonaqueous liquid crystals and gel phases in the binary system K-stearate/glycerol

The K-stearate/glycerol (KC18/Gl) binary system was studied at mole fractio ns of stearate of x(KC18) = 0.10, 0.25, 0.30 and 0.50. Small- and wide-angl e X-ray diffraction (XRD) measurements were combined with differential scan ning calorimetry (DSC) measurements at different temperatures. The investig ations were intended to verify the previously published phase diagram and w ere targeted at the confirmation of the gel-like (G(1)) phase and the isotr opic (I) phase. The XRD and DSC measurements lead to the conclusion that th e G(1) phase as well as the I phase, the existence of which had been propos ed from texture observations, do in fact not exist. Consequently, a correct ion of the preliminary phase diagram is given. This corrected phase diagram reveals the crystalline phase (C) <----> gel phase (G) <----> hexagonal ph ase (H-alpha) <----> isotropic, micellar phase phase transitions for low KC 18 concentrations of x(KC18) = 0.15-0.3 and the C <----> G <----> lamelIar phase (L-alpha) phase transitions for concentrations about or higher than x (KC18) = 0.35. The C, G, L-alpha and H-alpha phases have been further chara cterized by structural parameters (characteristic d values) as a function o f temperature. The phase transitions C <----> G, G <----> L-alpha and G <-- --> H-alpha correlate with sharp shifts in the d value of the first small-a ngle reflections.