Decanol pattern formation over a sessile aqueous decanoate droplet

Abstract

Spontaneous pattern formation in far from equilibrium systems plays important role in various disciplines including biology and reaction-diffusion chemistry. Recently, we have found that when a system consisting of a 1-decanol droplet and alkaline sodium decanoate aqueous solution is opened to the environment, and water evaporates, dramatic morphological changes of the decanol droplet are observed. Herein a series of experiments is performed to describe the effect of the initial condition (pH, molar concentration, volume of decanol) of the system on the pattern formation. Experiments showed that the timing of the pattern formation decreases with an increasing concentration of sodium decanoate and with increasing decanol volume. The timing of the pattern formation was significantly lower in basic pH conditions (~12). We propose an explanation of the pattern formation based on the diffusion of decanol into the sodium decanoate rich surface layer. The water evaporation leads to the evolution of the mixed interface, which becomes unstable and the pattern formation of 1-decanol occurs. Finally, our results indicate that the pattern formation of 1-decanol might be related to the co-micellization of sodium decanoate and 1-decanol.