How soft repulsion enhances the depletion mechanism

Lorenzo Rovigatti; Nicoletta Gnan; Alberto Parola; Emanuela Zaccarelli

doi:10.1039/c4sm02218a

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arXiv · 1409.0903

How soft repulsion enhances the depletion mechanism

Lorenzo Rovigatti·Nicoletta Gnan·Alberto Parola·Emanuela Zaccarelli

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Abstract

We investigate binary mixtures of large colloids interacting through soft potentials with small, ideal depletants. We show that softness has a dramatic effect on the resulting colloid-colloid effective potential when the depletant-to-colloid size ratio $q$ is small, with significant consequences on the colloidal phase behaviour. We also provide an exact relation that allows us to obtain the effective pair potential for {\it any} type of colloid-depletant interactions in the case of ideal depletants, without having to rely on complicated and expensive full-mixture simulations. We also show that soft repulsion among depletants further enhances the tendency of colloids to aggregate. Our theoretical and numerical results demonstrate that --- in the limit of small $q$ --- soft mixtures cannot be mapped onto hard systems and hence soft depletion is not a mere extension of the widely used Asakura-Oosawa potential.

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Lorenzo Rovigatti, Nicoletta Gnan, Alberto Parola, Emanuela Zaccarelli. 2014-09-02. How soft repulsion enhances the depletion mechanism. https://doi.org/10.1039/c4sm02218a

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