Inclusional association as studied by the drying dissipative structure. Part 2. Drying pattern of n-alkyltrimethylammonium bromide |
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Authors: | Tsuneo Okubo |
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Institution: | 1. Institute for Colloidal Organization, Hatoyama 3-1-112, Uji, Kyoto, 611-0012, Japan
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Abstract: | Macro- and microscopic drying patterns were observed on a cover glass and a watch glass during the course of dryness of aqueous solutions of a series of n-alkyltrimethylammonium bromides (alkyl: n-decyl, n-dodecyl, n-tetradecyl, and n-hexadecyl). The broad rings formed at the outside edges of the macroscopic patterns. Size of the initial liquid on the substrates, d i, that of the final broad ring, d f, and the ratio, d f/d i, changed as the surfactant concentration changed, and there appeared a bending point in each curve, which was found to correspond to the critical micelle concentration (cmc) of the surfactant. The cmc values evaluated from the d i, d f, and d f/d i values agreed well with the reference values reported previously. Cooperative drying processes of the convection, sedimentation, and solidification were supported. Microscopic drying patterns such as rod-like, dendritic, and granule-like patterns were observed, and they changed as a function of the carbon number of the alkyl groups, surfactant concentration, and the distance from the center of the pattern. |
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