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arXiv · 1410.4874

Impact of single-particle compressibility on the fluid-solid phase transition for ionic microgel suspensions

M. Pelaez-Fernandez·Anton Souslov·L. A. Lyon·Paul M. Goldbart·A. Fernandez-Nieves
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Abstract

We study ionic microgel suspensions composed of swollen particles for various single-particle stiffnesses. We measure the osmotic pressure $π$ of these suspensions and show that it is dominated by the contribution of free ions in solution. As this ionic osmotic pressure depends on the volume fraction of the suspension $ϕ$, we can determine $ϕ$ from $π$, even at volume fractions so high that the microgel particles are compressed. We find that the width of the fluid-solid phase coexistence, measured using $ϕ$, is larger than its hard-sphere value for the stiffer microgels that we study and progressively decreases for softer microgels. For sufficiently soft microgels, the suspensions are fluid-like, irrespective of volume fraction. By calculating the dependence on $ϕ$ of the mean volume of a microgel particle, we show that the behavior of the phase-coexistence width correlates with whether or not the microgel particles are compressed at the volume fractions corresponding to fluid-solid coexistence.

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M. Pelaez-Fernandez, Anton Souslov, L. A. Lyon, Paul M. Goldbart, A. Fernandez-Nieves. 2014-10-17. Impact of single-particle compressibility on the fluid-solid phase transition for ionic microgel suspensions. https://doi.org/10.1103/physrevlett.114.098303

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