Organization of Nano-disks of Laponite® in Soft Colloidal Systems

Lebovka, Nikolaï; Lisetski, L. N.; Булавин, Л. А.

doi:10.1007/978-3-030-21755-6_6

Cited by 11 publications

(13 citation statements)

References 120 publications

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“…The selected low and high concentrations correspond to the sol phase with a weak interaction between Lap particles and the boundary between the stable equilibrium gel and repulsive glass phases, respectively. − The strong interparticle correlations in Lap suspensions can be expected for critical volume concentrations above φ l * ≈ 0.96 h /[ d (1 + 2λ/ d )], where λ is the Debye screening length. This formula was obtained using the excluded volume considerations, and for Lap ( h ≈ 1 nm and d ≈ 25 nm), it predicts φ l * ≈ 3.5% ( C l * ≈ 8.4%) at a small concentration of the electrolyte (in salt-free water conditions, C i < 10 –4 M, i.e., λ ≈ d ) and φ l * ≈ 1.2% ( C l * ≈ 3%) at a high concentration of the electrolyte (i.e., at λ ≈ 0).…”

Section: Methodsmentioning

confidence: 99%

“…Laponite RD (Lap) represents synthetic clay composed of platelets with h ≈ 1 nm thickness and d ≈ 25 nm diameter. 1 Their faces possess a high negative charge, and it increases noticeably with an increase of pH from pH ≈ 2 to pH ≈ 8 and is stabilized in basic medium (at pH ≥ 8). At pH 10, the Lap edge surface is weakly positive, and the averaged surface charge of the particle is overall negative.…”

Section: Introductionmentioning

confidence: 99%

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Electrokinetic Behavior of Laponite RD in Aqueous Suspensions Containing Poly(ethylene oxide) and Cetyltrimethylammonium Bromide

2020

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The aqueous suspensions of Laponite RD (Lap) platelets demonstrate rich phase diagrams. Both poly(ethylene oxide) (PEO) and cetyltrimethylammonium bromide (CTAB) molecules competitively adsorb on the surface of Lap, and strong interactions between PEO and CTAB exist. The stability of ternary systems Lap + PEO + CTAB can be finely regulated by changing the balance of these interactions. The electrokinetic technique was used to study 0.065 and 2% wt Lap suspensions in the presence of different amounts of PEO of various molecular masses M w (400− 20,000 g/mol) and CTAB (0−1 mM). For 0.065% wt Lap suspension, the additives of PEO did not affect the position of the isoelectric point (IEP), but the impact of PEO in the regions below or above the IEP was significant, especially for a large M w . The observed effects were explained, accounting the model for the adsorption of PEO in the form of loops and tails as well as for the changes in the packing balance of CTAB and PEO on the surface of Lap. For 2% wt suspension, the strong effects of M w on the ζpotential and aggregation of particles were explained by screening the repulsive double layers by PEO chains, by bridging the Lap particles via PEO molecules, and by the impact of CTAB molecules on the bridging between Lap aggregates.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Electrokinetic Behavior of Laponite RD in Aqueous Suspensions Containing Poly(ethylene oxide) and Cetyltrimethylammonium Bromide

2020

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“…Recently, a new type of hybrid based on MWCNTs covered by platelets of Laponite RD® (Lap) was described [16] [38]). Adhesion of charged Lap nanoparticles on the surface of nanotubes improved their dispersion [10,29,[39][40][41][42][43][44].…”

Section: Fig 6 Adsorption Mechanisms Of Ctab On the Surface Of Carbmentioning

confidence: 99%

A short review on regulation of stability of aqueous suspensions of carbon nanotubes

Manilo¹,

Lebovka²,

Bárány³

2020

Him. Fiz. Tehnol. Poverhni

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This review analyses the authors' recent and related works on electrokinetic properties and colloidal stability of aqueous suspension of multi-walled carbon nanotubes (CNTs) in the presence of surfactants and nanoparticles. Selected adsorptive properties of carbon nanotubes are also considered.The applicability of classical theories of electrophoresis for description of electrophoretic mobility of carbon nanotubes is discussed. Examples on the ζ-potential of CNTs in aqueous suspensions as a function of pH and concentration of electrolytes (KCl, CaCl 2 and AlCl 3 ) are given. Additions of cetyltrimethylammonium bromide (CTAB) cationic surfactant below the critical micelle formation concentration (CMC) values give a reduction and then an overcharging the CNT surface because of accumulation of the surfactant ions in the Stern layer. At concentrations above CMC the substantial drop in ζ-potential is observed. It is due to the shift of the shear plane toward solution as a result of formation of hemi-micelles on the surface. An increase in the mass ratio of artificial mineral Laponite (Lap) in suspension (X) from 0 to 0.4 results in a monotonic decrease of the ζ-potential of CNT + Lap hybrids with reaching its plateau value ≈ -32 mV at X ≥ 0.4 that corresponds to the ζ-potential of "pure" Lap platelets. This evidences the high surface coverage of nanotubes surface with Lap at X ≥ 0.4.The major methods to improve the dispersibility of carbon nanotubes, their colloidal stability and adsorptive properties are briefly discussed, namely: stabilization in mixtures of water and organic solvents; functionalization by chemical treatment; stabilization by additives of surfactants or polymers and hybridization by addition of supplementary stabilizing nanoparticles. CNTs can be significantly debundled in "good" solvents, such as 1cyclohexyl-2-pyrrolidone, N,N-dimethylformamide, or N-methyl-2-pyrrolidone. It is demonstrated that the dispersibility of CNTs is a complex function of the type of surfactant, its concentration and the surfactant/CNTs ratio. The optimum concentration of CTAB to achieve homogeneous aqueous dispersion of carbon nanotubes was identified to be near the CMC. Additions of CTAB significantly modify the size distribution of CNTs and a sharp transition from small primary aggregates to large secondary aggregates at concentrations above CMC is observed. At optimal concentration of Lap the nanotube particles get well stabilized, and a stepwise increase of sedimentation stability is observed.We have shown also that CNT + Lap hybrids can be effectively used for removal of methylene blue dye from aqueous systems. The kinetics and mechanisms of adsorption are elucidated.

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“…The particle shape may affect the packing characteristics (e.g., packing density and coordination numbers) [1][2][3], the aggregation [4], and gravity-and vibration-induced segregation [5]. A lot of interest to such systems is stimulated by practical problems related with preparation of advanced materials [6,7] and composite films [8,9], filled with elongated nanoparticles, e.g., carbon nanotubes [10] and silicate platelets [11].…”

Section: Introductionmentioning

confidence: 99%

Connectedness percolation in the random sequential adsorption packings of elongated particles

Lebovka,

Tatochenko,

Vygornitskii

et al. 2020

Preprint

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Connectedness percolation phenomena in two-dimensional packings of elongated particles (discorectangles) were studied numerically. The packings were produced using random sequential adsorption (RSA) off-lattice model with preferential orientations of particles along a given direction. The partial ordering was characterized by order parameter S, with S = 0 for completely disordered films (random orientation of particles) and S = 1 for completely aligned particles along the horizontal direction x. The aspect ratio (length-to-width ratio) for the particles was varied within the range ε ∈ [1; 100]. Analysis of connectivity was performed assuming a core-shell structure of particles. The value of S affected the structure of packings, formation of long-range connectivity and electrical conductivity behavior. The effects were explained accounting for the competition between the particles' orientational degrees of freedom and the excluded volume effects. For aligned deposition, the anisotropy in electrical conductivity was observed and the values along alignment direction, σx, were larger than the values in perpendicular direction, σy. The anisotropy in localization of percolation threshold was also observed in finite sized packings, but it disappeared in the limit of infinitely large systems.

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Organization of Nano-disks of Laponite® in Soft Colloidal Systems

Cited by 11 publications

References 120 publications

Electrokinetic Behavior of Laponite RD in Aqueous Suspensions Containing Poly(ethylene oxide) and Cetyltrimethylammonium Bromide

Electrokinetic Behavior of Laponite RD in Aqueous Suspensions Containing Poly(ethylene oxide) and Cetyltrimethylammonium Bromide

A short review on regulation of stability of aqueous suspensions of carbon nanotubes

Connectedness percolation in the random sequential adsorption packings of elongated particles

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