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 an d butanol have been studied by scattering techniques. The neutron and X-ray scattering curves of these gels consist of a mix of the form fac tor of the aggregates and the structure factor of their organized inte racting domains. The results demonstrate that the aggregates are long and rigid fibers, the diameter (d) of which is slightly sensitive to t he solvent type: d = 160 Angstrom in decane and d = 192 Angstrom in bu tanol (assuming a homogeneous circular cross-sectional symmetry hypoth esis). The fibers are interconnected by ''junction zones'' in a random three-dimensional network. In decane, the structures of the aggregate s in the junction zones are lyotropic organizations obtained through a transformation from the hexagonal packing of the crystalline state. T he fibrils with a diameter of about 75.6 Angstrom, corresponding to ap proximately twice the molecular length, are ''swollen'' to ca. 102 Ang strom. In alcohols, the structural organization is closer to that of t he solid state and exhibits sharp interfaces with the solvent. The res ults obtained in the present studies are discussed in the context of p revious electron microscopy and fluorescence studies of CAB gels and c ompared to other structurally related gelators.