X-ray structural studies of lyotropic-cholesteric phases induced by addingcholesterol in the quaternary system hexadecyl dimethylethyl ammonium bromide/water/n-decanol/cholesterol

The results of X-ray structural studies of induced lyotropic cholesteric di sk-like phases Ch(D), rod-like phases Ch(C) and the lamellar phase L-alpha in the quaternary system hexadecyl dimethylethyl ammonium bromide (C(16)Me( 2)EABr)/water/n-decanol/cholesterol are described. For these X-ray measurem ents, a temperature-controlled SWAX camera was used The X-ray-curves of the the phases studied were evaluated as a function of the temperature and composition of the phases. Helix-formation occurs by so lubilization of the cholesterol into the N-D phase. During solubilization b oth the formanisotropy and the periodicity volume of the micelles were chan ged. Furthermore, the process of solubilization affects the average aggrega tion number per micelle and the average number of the solubilized cholester ol molecules per micelle. Structural details relating to the micelle parame ters of the Ch(D)- phase and Ch(C)-phase and also to the structural paramet ers of the L-alpha phase are discussed.