Universal Sol State Behavior and Gelation Kinetics in Mixed Clay Dispersions

Pujala, Ravi Kumar; Pawar, Nisha; Bohidar, H. B.

doi:10.1021/la1048453

Cited by 47 publications

(31 citation statements)

References 39 publications

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“…The irreversible dehydration transition is similar to the one we have reported in our previous studies [21]. Hardening of gel took place in MMT dispersions in the gel state is reported earlier.…”

Section: Observation Of Phase Separation and Equilibrium Gels And Phasupporting

confidence: 90%

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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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Section: Observation Of Phase Separation and Equilibrium Gels And Phasupporting

confidence: 90%

“…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].…”

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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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“…We dried the laponite powder for 2 h at 120°C to remove its moisture content. Laponite stock dispersions (1 %w/v) were prepared following the exact protocol described by Pujala et al [22]. The desired laponite concentration of 0.05 % (v/v) was achieved by adding a concentrated stock of laponite solution to the gelling gelatin sols.…”

Section: Preparation Of Gelatin a Organogel Nanocompositementioning

confidence: 99%

Antibacterial and Antifungal Activity of Biopolymers Modified with Ionic Liquid and Laponite

Sharma

Prakash

Rawat

et al. 2015

Appl Biochem Biotechnol

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In the present study, the antimicrobial properties of modified biopolymers such as gelatin and agar have been investigated. These biopolymers (agar and gelatin) are modified by dissolving in ionic liquid (IL) [1-ethyl-3-methylimidazolium chloride ([C2mim][Cl]) and 1-octyl-3-methyl imidazolium chloride ([C8mim][Cl])] solutions. It was noticed that agar-ionogel (Ag-IL), gelatin-ionogel (GB-IL), and gelatin organogel (gelatin-glycerol solution along with laponite, nanoclay) nanocomposite (GA-NC) formed are highly stable, optically clear, and transparent without any air bubbles. The antimicrobial activity of these (Ag-IL), (GB-IL), and GA-NC were analyzed for both gram-negative (Escherichia coli, Klebsiella pneumoniae) and gram-positive bacterial strains (Staphylococcus aureus and Staphylococcus pyogenes) and fungus A. niger, C. albicans. Antibacterial and antifungal activity studies were carried out at different dilutions such as 100, 99, and 90 % (v/v). It was found that Ag-IL, GB-IL, and individual IL ([C8mim][Cl]) exhibited superior antimicrobial activities, indicating that longer IL chain enhance the cell membrane permeability of S. aureus, S. pyogenes, and E. coli cells. However, GA-NC nanocomposite and [C2mim][Cl]-based composites does not exhibit any bacterial inhibition activity for all bacterial strains.

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“…But a systematic study of the aging dynamics has not been performed as yet. Recently, we have reported the sol-gel transition behavior in laponite-MMT mixed clay dispersions 6 . On the other hand, visco-elastic properties of many clay suspensions have been extensively probed [7][8][9][10] through face (−)/edge (+) (FE) attraction form "house of cards" structures in acidic medium and band-like structures are formed through cation-mediated face (−)/face (−) (FF) attraction in alkaline medium 13 .…”

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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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Universal Sol State Behavior and Gelation Kinetics in Mixed Clay Dispersions

Cited by 47 publications

References 39 publications

Phase Diagram of Aging Montmorillonite Dispersions

Phase Diagram of Aging Montmorillonite Dispersions

Antibacterial and Antifungal Activity of Biopolymers Modified with Ionic Liquid and Laponite

Spontaneous evolution of self-assembled phases from anisotropic colloidal dispersions

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