STRUCTURES OF ORGANOGELS BASED UPON CHOLESTERYL 4-(2-ANTHRYLOXY)BUTANOATE, A HIGHLY EFFICIENT LUMINESCING GELATOR - NEUTRON AND X-RAY SMALL-ANGLE SCATTERING INVESTIGATIONS

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 Angstrom in decane and d = 192 Angstrom 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 Angstrom, corresponding to approximately twice the molecular length, are ''swollen'' to ca. 102 Angstrom. 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.