LIQUID-CRYSTALLINE SOLVENTS AS MECHANISTIC PROBES .49. FACTORS INFLUENCING THE FORMATION OF THERMALLY REVERSIBLE GELS COMPRISED OF CHOLESTERYL 4-(2-ANTHRYLOXY)BUTANOATE IN HEXADECANE, 1-OCTANOL, OR THEIR MIXTURES

Gels containing small amounts of cholesteryl 4-(2-anthryloxy)butanoate (CAB) and a liquid component (hexadecane, 1-octanol, or their mixture s) have been investigated during the process of their formation upon c ooling from the respective isotropic phases by absorption, fluorescenc e, and excitation spectra. The spectra are compared to those of CAB in benzene, a solution which is not gelled. The results indicate that bu lk solvent properties, especially polarity, are more important than sp ecific solvent-CAB intermolecular interactions in determining the natu re 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 depend ing upon the protocol for cooling the precursor isotropic phases. In a ddition, cells whose wall separations are smaller than the diameters o f 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 .