Methodical developments for X-ray diffraction measurements and data analysis on lyotropic liquid crystals applied to K-soap/glycerol systems

X-ray diffraction (XRD) data acquisition and processing software measuremen ts on long-spacing binary systems, including adapted noise reduction algori thms, has been developed. The computation of XRD patterns has been summariz ed and the origin of the distinct patterns of long-spacing compounds has be en illustrated with the aid of such simulations. This also provided the pos sibility to evaluate the retrievable amount of information used for graphic al or numerical indexing programs. Numerical indexing programs were applied and limits of indexing method have been discussed. Differential scanning c alorimetry (DSC) measurements and temperature-dependent XRD measurements ha ve been carried out for the concentrations x(KC12) = 0.50 and 0.30 of the K -laurate/glycerol system. The analysis of the small- and wide-angle diffrac tograms in the various phase regions of the binary system as well as the DS C measurements provided the following results: - The creation of the lamellar phase extends over a temperature range of De lta T approximate to 20 K at a concentration of x(KC12) = 0.50. The lamella s show a reduced degree of order. - The crystalline-to-gel phase transition is accompanied by a leap in the d values corresponding to the small-angle reflexes. Also a distinct splittin g of the small-angle reflexes is observed within the gel phase. Simultaneou sly a rearrangement and intensity decay of the wide-angle tent xes occurs. Since some wide-angle reflexes are still present, the structure can be cons idered to have a partially reduced three-dimensional order. - During the creation of lamellar phases the d value decreases sharply with rising temperature. This decrease of d can be interpreted as a further dec ay of molecular order in the hydrocarbon chains of the K-laurate within the bilayers. - The XRD measurements correlate with the DSC data. according to our measur ements a revision of the phase diagram with respect to the actual extension of the gel-phase region was necessary.