An NMR Investigation of Water Self-Diffusion and Relaxation Rates in Controlled Ionic Strength Laponite Sols and Gels

Duval, Franck P.; Porion, Patrice; Faugère, Anne Marie; Damme, H. Van

doi:10.1006/jcis.2001.7806

Cited by 25 publications

(26 citation statements)

References 37 publications

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“…It means that the aged suspensions Laponite tactoids exfoliate to the same extent for the wide concentration range. This conclusion is consistent with the previous findings 16,17 based on the similar experiments. On the contrary, dependence of T 2 on Laponite concentration for suspensions of age of 1 day (Fig.1, open symbols) non-linear, meaning that for non-aged suspensions the specific surface area and the degree of particle exfoliation are concentration dependent.…”

Section: Resultssupporting

confidence: 94%

“…T 1 is measured by the inversion recovery method and T 2 is measured by the Carr-Purcell-Meiboom-Gill method. According to the two-phase fast-exchange model, the spin relaxation time T i depends linearly on specific area of wetted surface of the dispersed phase S NMR 16,17 : ... (1) where T fi is the spin relaxation time of hydrogen protons in free, or bulk, water, T bi -spin relaxation time of hydrogen protons in water bound to the particle surface, i is 1 (spin-lattice) or 2 (spin-spin), l -thickness of bound water layer (estimated as 1 nm 16,17 ), r is water density, CLaponite concentration (solid mass/ water mass),…”

Section: Methodsmentioning

confidence: 99%

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Exfoliation Dynamics of Laponite Clay in Aqueous Suspensions Studied by NMR Relaxometry

Karpovich¹,

Vlasova²,

Sapronova³

et al. 2016

Orient. J. Chem

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The interaction between Laponite and other constituents in complex systems greatly depends on its available surface area. We report a study of exfoliation dynamics of Laponite in aqueous suspensions by NMR relaxometry. It showed that Laponite particles exfoliate to the same extent in a concentration range of 0.5-3% w/w. Faster increase of specific wetted surface area of Laponite particles in more concentrated suspensions suggests faster exfoliation of disc-shaped Laponite platelets from the initial layered structure.

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Section: Resultssupporting

confidence: 94%

Section: Methodsmentioning

confidence: 99%

Exfoliation Dynamics of Laponite Clay in Aqueous Suspensions Studied by NMR Relaxometry

Karpovich¹,

Vlasova²,

Sapronova³

et al. 2016

Orient. J. Chem

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“…Ichikawa et al (1999) suggested using molecular dynamics such that the c value of montmorillonite completely dispersed in water is a few nm. Duval et al (1999Duval et al ( , 2001) estimated the c of hectorite to be 1À3 nm. These values from the literature are approximately equal to those listed in Table 5 suggesting that the methods employed in the present study are reasonable.…”

Section: Discussionmentioning

confidence: 99%

“…However, these equations are no more than phenomenological, and no explanation was made for the variation of a, b and a' values between different clay species. The purpose of the present study is to provide a physical explanation for the dependence of D/D 0 on w. The explanation is based on a hypothesis that bound or less mobile H 2 O layers near clay surfaces act as obstacles to diffusing unbound H 2 O molecules, and thereby decrease D/D 0 as w increases (Duval et al, 1999(Duval et al, , 2001Nakashima, 2001bNakashima, , 2002c. A diffusion model was introduced to discuss the effects of bound H 2 O layers on D/D 0 .…”

Section: Introductionmentioning

confidence: 99%

Diffusion of H₂O in Smectite Gels: Obstruction Effects of Bound H₂O Layers

Nakashima

2003

Clays and clay miner.

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In water-rich smectite gels, bound or less mobile H 2 O layers exist near negatively-charged clay platelets. These bound H 2 O layers are obstacles to the diffusion of unbound H 2 O molecules in the porespace, and therefore reduce the H 2 O self-diffusion coefficient, D, in the gel system as a whole. In this study, the self-diffusion coefficients of H 2 O molecules in water-rich gels of Na-rich smectites (montmorillonite, stevensite and hectorite) were measured by pulsed-gradient spin-echo proton nuclear magnetic resonance (NMR) to evaluate the effects of obstruction on D. The NMR results were interpreted using random-walk computer simulations which show that unbound H 2 O diffuses in the gels while avoiding randomly-placed obstacles (clay platelets sandwiched in immobilized bound H 2 O layers). A ratio (volume of the clay platelets and immobilized H 2 O layers)/(volume of clay platelets) was estimated for each water-rich gel. The results showed that the ratio was 8.92, 16.9, 3.32, 3.73 and 3.92 for Wyoming montmorillonite (45.74 wt.% clay), Tsukinuno montmorillonite (43.73 wt.% clay), synthetic stevensite (48.97 wt.% clay), and two synthetic hectorite samples (411.0 wt.% clay), respectively. The ratios suggest that the thickness of the immobilized H 2 O layers in the gels is 4.0, 8.0, 1.2, 1.4 and 1.5 nm, respectively, assuming that each clay particle in the gels consists of a single 1 nm-thick platelet. The present study confirmed that the obstruction effects of immobilized H 2 O layers near the clay surfaces are important in restricting the self-diffusion of unbound H 2 O in water-rich smectite gels.

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“…This small decrease in D m of about 3-7% is in agreement with the results obtained for other hydrogels at comparable gelator concentrations. 34 In these investigations, the diffusion coefficient was found to depend only on the solid volume fraction, but not on the macroscopic state 35 or on the cross-linker content. 36 Me 2 PE-C32-Me 2 PE.…”

Section: Resultsmentioning

confidence: 98%

Water Dynamics in Bolaamphiphile Hydrogels Investigated by ¹H NMR Relaxometry and Diffusometry

et al. 2010

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The dynamical properties of water in hydrogels formed by the bolaamphiphiles dotriacontane-1,32-diyl-bis[2-(trimethylammonio)ethylphosphate] (PC-C32-PC) and its head group derivative dotriacontane-1,32-diyl-bis[2-(dimethylammonio)ethylphosphate] (Me(2)PE-C32-Me(2)PE) were investigated by determining the transverse relaxation times and the mean diffusion coefficients of the water protons. T(2) distributions obtained for hydrogels containing only 1 mg/mL of PC-C32-PC or Me(2)PE-C32-Me(2)PE were found to be almost unchanged compared to that of pure deionized water. In a hydrogel containing 30 mg/mL PC-C32-PC, a small dynamical perturbation of the water molecules could be observed, since the obtained major peak in the T(2) distribution was found to be slightly broadened and shifted to lower T(2) values with respect to pure water. Moreover, a slightly decreased mean diffusion coefficient of the water molecules was determined for the hydrogel with 30 mg/mL PC-C32-PC. For 30 mg/mL Me(2)PE-C32-Me(2)PE at pH 5, the dynamical properties of water are significantly influenced by the presence of the bolaamphiphiles. Whereas the mean diffusion coefficient of water was again only slightly decreased, the relaxation behavior was found to be considerably changed. At room temperature, the major T(2) peak obtained for 30 mg/mL Me(2)PE-C32-Me(2)PE at pH 5 was significantly broadened and shifted to lower T(2) values compared to pure buffer. This broad monomodal peak becomes bimodal when the temperature is decreased to 5 °C. Increasing the temperature revealed that the structural changes of the bolaamphiphilic self-assemblies at 45 °C are reflected in the determined mean relaxation times (T(2m)). These results indicate the presence of a significant degree of structural heterogeneity in a hydrogel formed by 30 mg/mL Me(2)PE-C32-Me(2)PE at pH 5. By comparing the mean diffusion coefficients with the mean transverse relaxation times, the distance scale of these heterogeneities could be estimated to be in the range of 50 to 120-140 μm. They can most probably be ascribed to the existence of a considerable number of lamellar domains being formed besides the nanofibers in hydrogels with 30 mg/mL Me(2)PE-C32-Me(2)PE at pH 5. Upon storage, the phenomenon of syneresis was observed for this hydrogel, which corresponds to a growth of the lamellar domains to sizes between 140 and 190 μm.

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An NMR Investigation of Water Self-Diffusion and Relaxation Rates in Controlled Ionic Strength Laponite Sols and Gels

Cited by 25 publications

References 37 publications

Exfoliation Dynamics of Laponite Clay in Aqueous Suspensions Studied by NMR Relaxometry

Exfoliation Dynamics of Laponite Clay in Aqueous Suspensions Studied by NMR Relaxometry

Diffusion of H₂O in Smectite Gels: Obstruction Effects of Bound H₂O Layers

Water Dynamics in Bolaamphiphile Hydrogels Investigated by ¹H NMR Relaxometry and Diffusometry

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An NMR Investigation of Water Self-Diffusion and Relaxation Rates in Controlled Ionic Strength Laponite Sols and Gels

Cited by 25 publications

References 37 publications

Exfoliation Dynamics of Laponite Clay in Aqueous Suspensions Studied by NMR Relaxometry

Exfoliation Dynamics of Laponite Clay in Aqueous Suspensions Studied by NMR Relaxometry

Diffusion of H2O in Smectite Gels: Obstruction Effects of Bound H2O Layers

Water Dynamics in Bolaamphiphile Hydrogels Investigated by 1H NMR Relaxometry and Diffusometry

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Diffusion of H₂O in Smectite Gels: Obstruction Effects of Bound H₂O Layers

Water Dynamics in Bolaamphiphile Hydrogels Investigated by ¹H NMR Relaxometry and Diffusometry