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Some cationic surfactants such as cetyhrimethylammonium bromide (CTAB) show a very spectacular viscoelasticity in solution, in even very diluted states, with some aromatic substances added, such as salicylic acid. Formerly, the authors established that the remarkable solution behaviour was the result of the entanglement of such enormously elongated giant micelles, based on recognition of the existence of large aggregates, through direct observation of them as substantial images under the electron microscope.In this report, we further confirm the relation between micelle length and solution viscoelasticity after arbitrarily obtaining different size aggregates by altering the media pH, or by admixing shorter chain length surfactants than CTAB, which alone did not induce viscoelasticity.Key words: Cationic surfactant micelle, rod-like micelle, viscoelastic cationic surfactant system, electron micrographical micelle image, micelle length dependence on viscoelasticity.

When p-toluidine is added to an aqueous solution of CTAB, a remarkable increase of viscosity is accompanied by a spectacular elasticity. We detected the existence of extremely elongated rod-like micelles in electron micrographs. SAXS measurements indicate a closely packed array of cylindrical rod-like micelles, brought about when solutions flow through a thin capillary. A scattering maximum of d = 160A almost corresponds to the distance between the nearest neighbours of the cylindrical rod-like micelles. This value agrees with the diameter measured on electron micrographs. The second broad peak (d = 75_~) is assigned to a subsidiary maximum of the shape function of the cylinder with infinite length.Key words: _SAXS for cationic surfactant elongated micelle, cationic surfactant _additive systems, cationic surfactant viscoelastic solution, enormously elongated rod-like micelle, hexagonally arrayed elongated cationic surfactant micelle.

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Aqueous binary solutions of hexadecyltrimethylammonium bromide (HTAB) and o-iodophenol (OIPh) exhibit remarkable viscoelasticity. From the centrifuged sediment of such a solution a crystalline product was isolated on long standing. Elementary analysis of the crystals for C, H, and N gave an estimated composition consistent with a one-to-one molar ratio of the two substances. Comparisons with DSC and IR measurements on the crystal and equimolar mechanical mixtures suggested that a crystalline complex was formed characterized by low thermal stability.