On the basis of suggestive X-ray data, 14 aroyl L-cystine derivatives were designed, synthesized, and examined for their ability to gelate water. Several members of this amino acid family are remarkably effective aqueous gelators (the best being one that can rigidify aqueous solutions at 0.25 mM, ca. 0.01%, in less than 30 s!). A few of the analogues separate from water as crystals, indicating a close relationship between gelation and crystallization. All effective gelators self-assemble into fibrous structures that entrain the solvent in the capillary spaces among them. Hydrogen-bonding sites on the compounds that might stabilize the fibers were identified from specific substitutions that replace a hydrogen donor with a methyl group, enhance the hydrogen-accepting ability of a carbonyl oxygen, or promote the hydrogen-donating ability of an amide proton. The structural variations were characterized via minimal gelation concentrations and times, X-ray crystallography, light and electron microscopy, rheology, and calorimetry. The multiple techniques, applied to the diverse compounds, allowed an extensive search into the basis of gelation. It was learned, for example, that the compound with the lowest minimum gelator concentration and time also has one of the weakest gels (i.e., it has a low elastic modulus). This is attributed to kinetic effects that perturb the length of the fibers. It was also argued that π/π stacking, the carboxyl carbonyl (but not the carboxyl proton), and solubility factors all contribute to the stability of a fiber. Polymorphism also plays a role. Rheological studies at different temperatures show that certain gels are stable to a 1-Hz, 3-Pa oscillating shear stress at temperatures as high as 90 °C. Other gels have a "catastrophic" break at lower temperatures. Calorimetric data indicate a smooth transition from gel to sol as the temperature is increased. These and other issues are discussed in this "anatomy" of a gel.

A zwitterionic gemini surfactant forms a coacervate which is "elementary" in the sense that it consists of a single solute as opposed to the multicomponents (e.g., cetylpyridinium chloride/hexanol/water/NaCl) common in the coacervate literature. The gemini dissolves in water but then quickly separates as oily droplets which, despite the high water content of 83 wt %, are immiscible with water. Cryogenic temperature high-resolution scanning electron microscopy (cryo-HRSEM) examination of the droplets shows a distinct "sponge" structure. Although previously proposed for coacervate phases, a sponge morphology has never before been clearly depicted. The absence of previous electron microscopy (EM) pictures of the coacervate network is attributed to artifacts associated with transmission electron microscopy (TEM) methods, to the fragility of the coacervate toward physical perturbations, and to possible compositional changes with complex mixtures during sample preparation. When the gemini coacervate was exposed to mild shear, the honeycomb structure disappeared and was replaced by a lamellar phase.

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