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Issue 13, 2017
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Non-monotonic dependence of Pickering emulsion gel rheology on particle volume fraction

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Abstract

The microstructure of Pickering emulsion gels features a tenuous network of faceted droplets, bridged together by shared monolayers of particles. In this investigation, we use standard oscillatory rheometry in conjunction with confocal microscopy to gain a more comprehensive understanding of the role particle bridged interfaces have on the rheology of Pickering emulsion gels. The zero-shear elastic modulus of Pickering emulsion gels shows a non-monotonic dependence on particle loading, with three separate regimes of power-law and linear gel strengthening, and subsequent gel weakening. The transition from power-law to linear scaling is found to coincide with a peak in the volume fraction of particles that participate in bridging, which we indirectly calculate using measureable quantities, and the transition to gel weakening is shown to result from a loss in network connectivity at high particle loadings. These observations are explained via a simple representation of how Pickering emulsion gels arise from an initial population of partially-covered droplets. Based on these considerations, we propose a combined variable related to the initial droplet coverage, to be used in reporting and rationalizing the rheology of Pickering emulsion gels. We demonstrate the applicability of this variable with Pickering emulsions prepared at variable fluid ratios and with different-sized colloidal particles. The results of our investigation have important implications for many technological applications that utilize solid stabilized multi-phase emulsions and require a priori knowledge or engineering of their flow characteristics.

Graphical abstract: Non-monotonic dependence of Pickering emulsion gel rheology on particle volume fraction

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Publication details

The article was received on 22 Dec 2016, accepted on 11 Mar 2017 and first published on 13 Mar 2017


Article type: Paper
DOI: 10.1039/C6SM02858F
Citation: Soft Matter, 2017,13, 2513-2522
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    Non-monotonic dependence of Pickering emulsion gel rheology on particle volume fraction

    M. Kaganyuk and A. Mohraz, Soft Matter, 2017, 13, 2513
    DOI: 10.1039/C6SM02858F

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