Phase Diagrams of Wyoming Na-Montmorillonite Clay. Influence of Particle Anisotropy

Michot, Laurent J.; Bihannic, Isabelle; Porsch, Katharina; Maddi, Solange; Baravian, Christophe; Mougel, Julien; Levitz, Pierre

doi:10.1021/la0489108

Cited by 170 publications

(243 citation statements)

References 72 publications

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“…At medium and low NaCl concentration, a gel also formed at MMT concentration above 3 wt%. This observation is in line with previous studies on MMT [25,42,49] and Laponite [26,52]. However, the clay concentration where the sol/gel transition occurred varies slightly, depending on the origin of the clay.…”

Section: Results (A) Phase Diagram Of Pure Montmorillonitesupporting

confidence: 92%

“…The samples were poured out from the vials and left to rest 5 min before each measurement. The elastic modulus G and the viscous modulus G were obtained and the following criteria were used to identify a gel: (i) G is obviously higher than G and (ii) G does not vary much over the whole frequency range [25]. …”

Section: (C) Rheologymentioning

confidence: 99%

“…Yet, the effect of Jeffamine was not sufficient to allow a liquid crystalline phase to form. 4 Na 0.68 [25]. The purification and fractionation of the clay was described in detail in a previous study [47].…”

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confidence: 99%

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Modifying the structure and flow behaviour of aqueous montmorillonite suspensions with surfactant

Cui

Pizzey

Duijneveldt

2013

Phil. Trans. R. Soc. A.

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Colloidal suspensions of plate-like particles undergo a variety of phase transitions. The predicted isotropic/ nematic transition is often pre-empted by a sol/gel transition, especially in suspensions of the most commonly used natural swelling clay montmorillonite (MMT). A number of factors, including charge interactions, flexibility and salt concentration, may contribute to this competition. In this study, the effect of surfactant adsorption on suspensions of MMT was studied using rheology, small-angle X-ray scattering, static light scattering and optical microscopy. The addition of a polyetheramine surfactant reduced the moduli of the system and shifted the sol/gel transition to a much higher clay concentration, compared with suspensions of bare clay particles. Yet, scattering data revealed no change in suspension structure on length scales up to around a micrometre. Primary aggregates remain at this length scale and no nematic phase is formed. There is, however, a change in structure at large length scales (of order 20 µm) where light scattering indicates the presence of string-like aggregates that disappear on addition of surfactant. Microscope images of dried suspensions also revealed a string-like structure. The dried strings show strong birefringence and may consist of concentric cylinders, self-assembled from clay sheets.

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Section: Results (A) Phase Diagram Of Pure Montmorillonitesupporting

confidence: 92%

Section: (C) Rheologymentioning

confidence: 99%

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Modifying the structure and flow behaviour of aqueous montmorillonite suspensions with surfactant

Cui

Pizzey

Duijneveldt

2013

Phil. Trans. R. Soc. A.

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“…At concentrations above the repulsive gel transition, where the hydrodynamic volumes swept out by the particles overlap, a yield stress develops, and the suspension becomes viscoplastic. The yield stress depends on the clay volume fraction, the particle size, 88 shape, 89,90 and localisation of the charge in the clay layer structure. 109 The gel phase of these particle suspensions is quite "fragile", yielding under small strains of $1-10 percent, (unlike polymer gels where yield strains of several hundred percent are common).…”

Section: Smectite Suspension Rheologymentioning

confidence: 99%

Smectite clay – inorganic nanoparticle mixed suspensions: phase behaviour and rheology

2015

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Smectite clay minerals and their suspensions have long been of both great scientific and applications interest and continue to display a remarkable range of new and interesting behaviour. Recently there has been an increasing interest in the properties of mixed suspensions of such clays with nanoparticles of different size, shape and charge. This review aims to summarize the current status of research in this area focusing on phase behaviour and rheological properties. We will emphasize the rich range of data that has emerged for these systems and the challenges they present for future investigations. The review starts with a brief overview of the behaviour and current understanding of pure smectite clays and their suspensions. We then cover the work on smectite clay-inorganic nanoparticle mixed suspensions according to the shape and charge of the nanoparticles -spheres, rods and plates either positively or negatively charged. We conclude with a summary of the overarching trends that emerge from these studies and indicate where gaps in our understanding need further research for better understanding the underlying chemistry and physics.

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“…The phase diagram of MMT is least explored in the literature, though some attempts in that direction have been made in the past 4,5 . But a systematic study of the aging dynamics has not been performed as yet.…”

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confidence: 99%

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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Phase Diagrams of Wyoming Na-Montmorillonite Clay. Influence of Particle Anisotropy

Cited by 170 publications

References 72 publications

Modifying the structure and flow behaviour of aqueous montmorillonite suspensions with surfactant

Modifying the structure and flow behaviour of aqueous montmorillonite suspensions with surfactant

Smectite clay – inorganic nanoparticle mixed suspensions: phase behaviour and rheology

Spontaneous evolution of self-assembled phases from anisotropic colloidal dispersions

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