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 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.