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Issue 34, 2019
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Equation of state of colloidal membranes

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In the presence of a non-adsorbing polymer, monodisperse rod-like colloids assemble into one-rod-length thick liquid-like monolayers, called colloidal membranes. The density of the rods within a colloidal membrane is determined by a balance between the osmotic pressure exerted by the enveloping polymer suspension and the repulsion between the colloidal rods. We developed a microfluidic device for continuously observing an isolated membrane while dynamically controlling the osmotic pressure of the polymer suspension. Using this technology we measured the membrane rod density over a range of osmotic pressures than is wider that what is accessible in equilibrium samples. With increasing density we observed a first-order phase transition, in which the in-plane membrane order transforms from a 2D fluid into a 2D solid. In the limit of low osmotic pressures, we measured the rate at which individual rods evaporate from the membrane. The developed microfluidic technique could have wide applicability for in situ investigation of various soft materials and how their properties depend on the solvent composition.

Graphical abstract: Equation of state of colloidal membranes

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Publication details

The article was received on 25 May 2019, accepted on 26 Jul 2019 and first published on 29 Jul 2019

Article type: Paper
DOI: 10.1039/C9SM01054H
Soft Matter, 2019,15, 6791-6802

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    Equation of state of colloidal membranes

    A. J. Balchunas, R. A. Cabanas, M. J. Zakhary, T. Gibaud, S. Fraden, P. Sharma, M. F. Hagan and Z. Dogic, Soft Matter, 2019, 15, 6791
    DOI: 10.1039/C9SM01054H

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