Towards understanding the empty liquid of colloidal platelets: vapour–liquid phase coexistence of square-well oblate ellipsoids

Meneses-Juárez, Efraín; Varga, Szabolcs; Orea, Pedro; Odriozola, Gerardo

doi:10.1039/c3sm50264c

Cited by 18 publications

(21 citation statements)

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“…Remarkably the aforesaid phenomena was independent of platelet aspect ratio. Most recently Meneses-Juarez and co-workers have observed the formation of a liquid phase with vanishing density, called an empty liquid [18]. Based on the data in hand, we are unable to vouch for the existence of arrested empty liquids in our t w -c phase diagram.…”

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confidence: 44%

“…Figure 2a depicts the picture of phase separation at lower concentrations below c g and the formation of equilibrium gels above c g . Stunningly, the phase separation terminates at a finite but very low clay concentration, above which the samples remain in a homogeneous arrested state, which may be called an empty liquid 16,18 . 27 .…”

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confidence: 99%

“…The presence of adsorbed water covering the clay particles produces characteristic cohesive plastic behavior of clay minerals. Recent studies described clay as patchy colloids with limited valance which have the ability to form empty liquids with low coordination number, and equilibrium gels which do not necessarily follow an underlying phase separation process 16,18 .…”

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Spontaneous evolution of self-assembled phases from anisotropic colloidal dispersions

2015

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We investigate the spontaneous evolution of various self-assembled phase states from a homogeneous aqueous dispersion of high-aspect ratio Montmorillonite (Na Cloisite) nanoclay platelets grounded on the observations made over a period of 3.5 years. We have established the t w -c phase diagram for this system for the first time in salt-free suspensions under normal pH conditions using rheology experiments and have detected that these suspensions do undergo nontrivial phase evolution and aging dynamics. Distinctive phase separation, equilibrium fluid and equilibrium gels in the t w -c phase space are discovered. Cole-Cole plots derived from rheology measurements suggested the presence of inter connected network-like structures for c > c g, c g being the gelation concentration. All dispersions formed stable sols during the initial time, and with aging networklike structures were found to form via two routes: one for c < c g , by phase separation and another for c > c g , through equilibrium gelation. This has invoked and called for a revisit of the phase diagram of aging MMT dispersions.Emergence of anisotropic interaction between patchy colloids give rise to an array of unusual and novel soft materials like empty liquids with vanishing density, arrested networks and equilibrium gels which do not necessarily follow an underlying phase separation process to be borne. Recent research in patchy colloids has thrown up possibilities for intelligent design and development of structured nano-assemblies following a bottomup approach. These systems are inherently rich in dynamics, and a hierarchy of time and length scales adequately defines the properties of the soft matter so formed. Phase stability of dispersions of anisotropic particles has been of much scientific debate in the recent times. Many phase diagrams have been conceived and proposed for colloidal particles having different degree of geometrical anisotropy, namely rods, platelets, disks etc in their dispersion states [1][2][3] . Clays are discotic platelets with varying aspect ratio and surface charge density, and their dispersions exhibit an array of soft matter phases that evolve with waiting time t w as well as solid concentration c. Thus, the t w -c phase diagram is replete with non-trivial and equilibrium soft matter phases continuously evolving with time. From the application point of view, suspensions of clays offer unique properties, including their ability to form arrested states like gels, glasses and liquid crystalline structures under ambient conditions. Remarkably, compared to spherical colloids, clay platelets exhibit gel and glass phases at very low concentrations, which owe their origin to their unique geometrical structure and surface charge heterogeneity.In this work we demonstrate the spontaneous evolution of various self-assembled phases from a homogeneous aqueous dispersion of Montmorillonite (MMT, platelet diameter 250 nm and thickness 1 nm) nanoclay platelets based on the observations made over a period of 3.5 years. We have established ...

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Spontaneous evolution of self-assembled phases from anisotropic colloidal dispersions

2015

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“…The gel formation, occurring at sufficiently high T in the absence of phase separation, has been interpreted in terms of reversible equilibrium gels [85], in analogy with patchy particle systems. Finally, a series of works by Odriozola and coworkers [55,86,87] have investigated the role of the shape in attractive particles, by examining the phase behavior of attractive ellipsoids (see Fig. 2).…”

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confidence: 99%

“…In order, a patchy particle model [53], the DNA-nanostars, the laponite discotic platelet [54], oblate and prolate attractive ellipsoids [55], the Fmoc-FF molecule [56] and a protein in the presence of multivalent salt providing limited interactions [57].…”

Section: Figmentioning

confidence: 99%

Equilibrium gels of limited valence colloids

Sciortino

Zaccarelli

2017

Current Opinion in Colloid & Interface Science

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Gels are low-packing arrested states of matter which are able to support stress. On cooling, limited valence colloidal particles form open networks stabilized by the progressive increase of the interparticle bond lifetime. These gels, named equilibrium gels, are the focus of this review article. Differently from other types of colloidal gels, equilibrium gels do not require an underlying phase separation to form. Oppositely, they form in a region of densities deprived of thermodynamic instabilities. Limited valence equilibrium gels neither coarsen nor age with time.

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Phase Diagram of Aging Montmorillonite Dispersions

Pujala

2014

Dispersion Stability, Microstructure and Phase Transition of Anisotropic Nanodiscs

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This chapter investigates the phase diagram of extensively aged MMT dispersions. Formation of gel through different routes is reported. Distinctive phase separation, equilibrium fluid and equilibrium gels in the t w -c phase space are observed for the first time ever in MMT dispersions ( Fig. 5.1). IntroductionPhase stability of dispersions of anisotropic particles has been of much scientific debate in the recent times. Many phase diagrams have been conceived and proposed for colloidal particles having different degree of geometrical anisotropy, namely rods, platelets, disks etc. in their dispersion states [2,28,29]. Spherical colloidal particles have been studied extensively in the literature. Clays are discotic platelets with varying aspect ratio and surface charge density. Because of this clay dispersions have exhibited non-trivial and rich phase diagrams, which have attracted much attention in recent years. Suspensions of clays have unique properties, including the ability to form arrested states like gels, glasses and liquid crystalline structures under ambient conditions as function of aging time and solid concentration. Remarkably, compared to spherical colloids, clay platelets exhibit gel and glass phases at very low concentrations which owe their origin to their structure and surface charge heterogeneity.Montmorillonite (MMT) is one of the natural clays, which has high aspect ratio and is a macroscopically swelling, 'active' clay that has the capacity for taking up large amounts of water to form stable gels. The phase diagram of MMT is least explored in the literature, though some attempts in that direction have been made in the past Michot et al. [16]. Michot et al. [16] studied the phase diagram of MMT using different aspect ratio samples. Recently, we have reported the sol and gel transition behavior of laponite-MMT mixed clay dispersions [21]. On the other hand, visco-elastic properties of MMT suspensions have extensively reported [4,8,17,22,25,26]. For instance, rheology behaviour of bentonite slurries as a function of pH, molar ratio of Na + /Ca +2 and with a range of additives such as pyrophosphate, polyphosphate [31]

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Towards understanding the empty liquid of colloidal platelets: vapour–liquid phase coexistence of square-well oblate ellipsoids

Cited by 18 publications

References 48 publications

Spontaneous evolution of self-assembled phases from anisotropic colloidal dispersions

Spontaneous evolution of self-assembled phases from anisotropic colloidal dispersions

Equilibrium gels of limited valence colloids

Phase Diagram of Aging Montmorillonite Dispersions

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