Dissipative structures formed in the course of drying the aqueous solution of n-dodecyltrimethylammonium chloride on a cover glass

Macroscopic and microscopic dissipative structural patterns are formed in the course of drying an aqueous solution of n-dodecyltrimethylammonium chloride on a cover glass. Broad ring patterns of the hill accumulate with detergent molecules to form around the outside edges of the film solution in the macroscopic scale. The drying time ( T) and the pattern area ( S) decrease and increase respectively, as the detergent concentration increases. T decreases significantly as the ethanol fraction increases in the aqueous ethanol mixtures, whereas S increases as the fraction increases. Both T and S decrease as the concentrations of KCl, CaCl ₂ or LaCl ₃ increase. Cross-, branch-, and arc-like microscopic patterns are observed in the separated block regions. The convection of water and detergents at different rates under gravity and the translational and rotational Brownian movement of the latter are important for macroscopic pattern formation. Microscopic patterns are determined by the translational Brownian diffusion of the detergent molecules and the electrostatic and the hydrophobic interactions between the detergents and/or between the detergent and cell wall in the course of the solidification.