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Issue 5, 2012
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The unstable and expanding interface between reacting liquids: theoretical interpretation of negative surface tension

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Abstract

When a chemical reaction between two immiscible liquids creates surfactant molecules at the interface between them, the interfacial surface tension decreases with increasing amount of surfactant. In particular, an interfacial reaction that is faster than the time scale of system's equilibration can cause a marked increase in the interfacial area due to the surface tension becoming effectively negative. Under these highly nonequilibrium conditions, the interface roughens and develops a variety of interfacial structures ranging from “ripples” to micelle-like formations; in systems of droplets, this process can lead to cycles of droplet elongation and self-division into smaller progenies. In the present work, the emergence and implications of negative surface tension over a “reactive” interface are studied theoretically and using computer simulations. The onset of interfacial instabilities can be described analytically using the methods of linear stability analysis of the continuum theory. For longer times, Molecular Dynamics simulations are implemented which reproduce the formation and increase of interfacial “ripples” at the initial stage, when the interface is a monolayer of surfactant, and widening of the reactive/mixing layer at later times.

Graphical abstract: The unstable and expanding interface between reacting liquids: theoretical interpretation of negative surface tension

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Publication details

The article was received on 19 Aug 2011, accepted on 04 Nov 2011 and first published on 15 Dec 2011


Article type: Paper
DOI: 10.1039/C1SM06590D
Citation: Soft Matter, 2012,8, 1601-1608
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    The unstable and expanding interface between reacting liquids: theoretical interpretation of negative surface tension

    A. Z. Patashinski, R. Orlik, K. Paclawski, M. A. Ratner and B. A. Grzybowski, Soft Matter, 2012, 8, 1601
    DOI: 10.1039/C1SM06590D

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