Structural and calorimetric investigations on nonaqueous liquid crystals and gel phases in the binary system K-stearate/glycerol |
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Authors: | A. Hieke H.-D. Dörfler |
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Affiliation: | (1) TU Dresden, Institut für Physikalische Chemie und Elektrochemie; Kolloidchemie Mommsenstrasse 13 D-01062 Dresden Germany, DE |
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Abstract: | The K-stearate/glycerol (KC18/Gl) binary system was studied at mole fractions of stearate of x KC18 = 0.10, 0.25, 0.30 and 0.50. Small- and wide-angle X-ray diffraction (XRD) measurements were combined with differential scanning calorimetry (DSC) measurements at different temperatures. The investigations were intended to verify the previously published phase diagram and were targeted at the confirmation of the gel-like (G1) phase and the isotropic (I) phase. The XRD and DSC measurements lead to the conclusion that the G1 phase as well as the I phase, the existence of which had been proposed from texture observations, do in fact not exist. Consequently, a correction of the preliminary phase diagram is given. This corrected phase diagram reveals the crystalline phase (C) ⇆ gel phase (G) ⇆ hexagonal phase (Hα) ⇆ isotropic, micellar phase phase transitions for low KC18 concentrations of x KC18 = 0.15–0.3 and the C ⇆ G ⇆ lamellar phase (Lα) phase transitions for concentrations about or higher than x KC18 = 0.35. The C, G, Lα and Hα phases have been further characterized by structural parameters (characteristic d values) as a function of temperature. The phase transitions C ⇆ G, G ⇆ Lα and G ⇆ Hα correlate with sharp shifts in the d value of the first small-angle reflections. Received: 20 April 1999 Accepted: 28 July 1999 |
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Keywords: | Nonaqueous liquid crystals Gel phase X-ray diffraction Calorimetry K-stearate |
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