Defying the Gibbs Phase Rule: Evidence for an Entropy-Driven Quintuple Point in Colloid-Polymer Mixtures

Peters, Vincent F. D.; Vis, Mark; García, Álvaro González; Wensink, H. H.; Tuinier, Remco

doi:10.1103/physrevlett.125.127803

Cited by 25 publications

(25 citation statements)

References 51 publications

(84 reference statements)

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“…For this reason, the two-phase N–ABC or I–SmA coexistences do not appear in this case. The principle behind the four-phase I–N–SmA–ABC coexistence is similar to that reported for plate–polymer mixtures and the I–N–SmA–AAA coexistence reported for rod–polymer mixtures . However, for the plate–polymer mixtures of ref , only three structurally different phases were considered, so four-phase coexistence was solely observed in combination with an isostructural coexistence.…”

Section: Resultssupporting

confidence: 80%

Multiphase Coexistences in Rod–Polymer Mixtures

et al. 2021

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Using recently derived analytical equations of state for hard rod dispersions, we predict the phase behavior of athermal rod−polymer mixtures with free volume theory. The rods are modeled as hard spherocylinders, while the nonadsorbing polymer chains are described as penetrable hard spheres. It is demonstrated that all of the different types of phase states that are stable for pure colloidal rod dispersions can coexist with any combination of these phases if polymers are added, depending on the concentrations, rod aspect ratio, and polymer−rod size ratio. This includes novel two-, three-, and four-phase coexistences and isostructural coexistences between dilute and concentrated phases of the same kind, even for the more ordered (liquid) crystal phases. This work provides insight into the conditions at which particular multiphase coexistences are expected for well-defined model colloidal rod−polymer mixtures. We provide a quantitative map detailing the various types of isostructural coexistences, which confirms an early qualitative hypothesis by Bolhuis et al. (J. Chem. Phys. 107, 1997 1551.

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Section: Resultssupporting

confidence: 80%

Multiphase Coexistences in Rod–Polymer Mixtures

et al. 2021

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“…Hence, as pointed out in other works 21,40 , the occurrence of say five layers in a stacking sequence does not imply the existence of a quintuple point in the bulk phase diagram. Such multi-phase bulk coexisting points can exist in binary mixtures 56,57 for specific interparticle interactions but are unrelated to the occurrence of several layers in sedimentation.…”

Section: Discussionmentioning

confidence: 99%

Gravity-induced phase phenomena in plate-rod colloidal mixtures

2021

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Gravity can affect colloidal suspensions since for micrometer-sized particles gravitational and thermal energies can be comparable over vertical length scales of a few millimeters. In mixtures, each species possesses a different buoyant mass, which can make experimental results counter-intuitive and difficult to interpret. Here, we revisit from a theoretical perspective iconic sedimentation-diffusion-equilibrium experiments on colloidal plate-rod mixtures by van der Kooij and Lekkerkerker. We reproduce their findings, including the observation of five different mesophases in a single cuvette. Using sedimentation path theory, we incorporate gravity into a microscopic theory for the bulk of a plate-rod mixture. We also show how to disentangle the effects of gravity from sedimentation experiments to obtain the bulk behavior and make predictions that can be experimentally tested. These include changes in the sequence by altering the sample height. We demonstrate that both buoyant mass ratio and sample height form control parameters to study bulk phase behavior.

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“…Furthermore, rod-like particles can form ordered structures, i.e. liquid crystals and columnar phases, at high concentrations [22][23][24] .…”

Section: Introductionmentioning

confidence: 99%

Phase stability of colloidal mixtures of spheres and rods

Opdam

Guu

Schelling

et al. 2021

The Journal of Chemical Physics

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We determined the phase boundaries of aqueous mixtures containing colloidal rod-like fd-viruses and polystyrene spheres using diffusing-wave spectroscopy and compared the results with free volume theory predictions. Excluded volume interactions in mixtures of colloidal rods and spheres lead to mediated depletion interactions. The strength and range of this attractive interaction depend on the concentrations of the particles, the length L and diameter D of the rods and the radius R of the spheres. At strong enough attraction, this depletion interaction leads to phase separation. We experimentally determined the rod and sphere concentrations where these phase transitions occur by systematically varying the size ratios L/R and D/R and the aspect ratio L/D. This was done by using spheres with different radii and modifying the effective diameter of the rods through either the ionic strength of the buffer or anchoring a polymeric brush to the surface of the rods. The observed phase transitions were from a binary fluid to a colloidal gas/liquid phase coexistence which occurred already at very low concentrations due to the depletion efficiency of highly anisotropic rods. The experimentally measured phase transitions were compared to phase boundaries obtained using free volume theory (FVT), a well established theory for calculating the phase behaviour of colloidal particles mixed with depletants. We find good correspondence between the experimental phase transitions and the theoretical FVT model where the excluded volume of the rod-like depletants was explicitly accounted for in both the reservoir and the system.

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Defying the Gibbs Phase Rule: Evidence for an Entropy-Driven Quintuple Point in Colloid-Polymer Mixtures

Cited by 25 publications

References 51 publications

Multiphase Coexistences in Rod–Polymer Mixtures

Multiphase Coexistences in Rod–Polymer Mixtures

Gravity-induced phase phenomena in plate-rod colloidal mixtures

Phase stability of colloidal mixtures of spheres and rods

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