MICROSTRUCTURAL CHARACTERIZATION OF NOVEL PHENOLIC ORGANOGELS THROUGHHIGH-RESOLUTION NMR-SPECTROSCOPY

We have recently shown that novel organogels can be formed through hyd rogen-bonding associations between a variety of phenols and the anioni c head group of the surfactant sodium bis(2-ethylhexyl)sulfosuccinate (AOT) in a nonpolar solvent. These hydrogen-bonding forces can be easi ly broken by simple means such as by heating or, more interestingly, b y exposure to moisture, causing the gel to soften or melt. Here, we in vestigate the gel microstructure and the nature of;molecular organizat ion by high-resolution NMR spectroscopy. The studies indicate that the motion of the phenol molecules is severely restricted, while the surf actant is apparently capable of relatively unhindered motion on the NM R time scale. From H-1 coupling constant information, it appears that gel formation does not significantly affect the surfactant equilibrium rotamer distribution but decreases the energy barrier for interconver sion. A picture of the gel is constructed to account for the observed spectral features.