Organogels of cholesteryl 4-(2-anthryloxy)butanoate (CAB) in decane and butanol have been studied by scattering techniques. The neutron and X-ray scattering curves of these gels consist of a mix of the form factor of the aggregates and the structure factor of their organized interacting domains. The results demonstrate that the aggregates are long and rigid fibers, the diameter (d) of which is slightly sensitive to the solvent type: d = 160 Á in decane and d = 192 Á in butanol (assuming a homogeneous circular cross-sectional symmetry hypothesis). The fibers are interconnected by "junction zones" in a random three-dimensional network. In decane, the structures of the aggregates in the junction zones are lyotropic organizations obtained through a transformation from the hexagonal packing of the crystalline state. The fibrils with a diameter of about 75.6 Á, corresponding to approximately twice the molecular length, are "swollen" to ca. 102 Á. In alcohols, the structural organization is closer to that of the solid state and exhibits sharp interfaces with the solvent. The results obtained in the present studies are discussed in the context of previous electron microscopy and fluorescence studies of CAB gels and compared to other structurally related gelators.
Gels containing small amounts of cholesteryl 4-(2-anthryloxy)butanoate (CAB) and a liquid component (hexadecane, 1-octanol, or their mixtures) have been investigated during the process of their formation upon cooling from the respective isotropic phases by absorption, fluorescence, and excitation spectra. The spectra are compared to those of CAB in benzene, a solution which is not gelled. The results indicate that bulk solvent properties, especially polarity, are more important than specific solvent-CAB intermolecular interactions in determining the nature of the gel phases formed, but even the dependence on bulk polarity is complex. When 80-85/20-15 (Wt/wt) 1-octanol/hexadecane compositions are employed with CAB, two different gel types can be isolated depending upon the protocol for cooling the precursor isotropic phases. In addition, cells whose wall separations are smaller than the diameters of the colloidal units which are assembled from CAB strands in the gels inhibit formation. The process of gelation in these systems is shown to be very complex, but manipulable by a surprising variety of factors.
Luminescent organogels formed by the small molecules cholesteryl 4-(2anthryloxy) butanoate (CAB) and 2,3-bis-n-decyloxyanthracene (DDOA) in decane and alcohol solvents have been studied by scattering techniques. The results are compared with previous studies of hydrocarbon-based gels of an androstanol derivative (STNH) analogue. Rheology experiments confirm that the materials, obtained through a sharp transition from a solution to a soft solid, have all of the characteristics of gels. For instance, the thermoreversible DDOA-octan-1-01 gel exhibits a yield stress (a* x 550 Pa at C = 1 wt.%), and its elasticity (G' x lo4 Pa) suggests the existence of numerous structural results have been confirmed by electron microscopy measurements. Structural correlations derived from studies of this family of gelators may bear upon the gelation process.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.