Structural investigation of hectorite aqueous suspensions by dielectric microscopy and small-angle neutron scattering coupling with rheological measurement

Iwase, Hiroki; Ogura, Toshihiro; Sakuma, Hiroshi; Tamura, Kenji; Fukushima, Yoshiaki

doi:10.1016/j.clay.2018.02.016

Cited by 18 publications

(5 citation statements)

References 14 publications

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“…Although there have been no prior Rheo-SANS studies of Nafion dispersions and so we cannot perform a direct comparison with previous data, similar isotropic SANS/SAXS patterns have been reported for aqueous dispersions of disklike particles of Laponite clay, along with marked shear thinning. − The isotropic patterns in the Rheo-SANS data (1–100 nm) suggest tightly stacked yet randomly oriented local structures resulting from strong electrostatic repulsion, similar to our Nafion data. In the case of these clay dispersions, owing to the large difference in the refractive indices of the clay and solvent, the presence of large domains could be examined using the Rheo-SALS technique .…”

Section: Resultssupporting

confidence: 85%

Nanostructures and Viscosities of Nafion Dispersions in Water/Ethanol from Dilute to Concentrated Regimes

Gupit

Maekawa

et al. 2020

Macromolecules

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Nafion is a fluorocarbon polymer, commonly used as a proton exchange membrane in fuel cells because of its excellent thermal and mechanical stabilities. However, the basic properties of Nafion, such as its nanostructures and rheological behavior, remain unclear because the morphology of this material is highly sensitive to its processing history. The present work involved a systematic analysis of both the structural and rheological properties of Nafion dispersions carefully prepared using a standard procedure, ranging from dilute (0.1 wt %) to highly concentrated (30 wt %) conditions. Small-angle X-ray scattering confirmed the cylindrical structure of Nafion in dispersion and the unique interactions of Nafion particles acting as polyelectrolytes. Three different scaling relationships involving the zero-shear viscosities of the Nafion dispersions were determined for specific concentration regimes. However, at the upper concentration limit of approximately 30 wt %, the viscosity greatly deviated from these scaling relationships and significant shear thinning was observed. Simultaneous analyses using rheology and small-angle neutron scattering determined fully isotropic spatial correlations on a length scale of less than 60 nm, even when high shear was applied. These results indicate a tightly entangled local structure and the presence of large yet weakly interacting domains that are responsible for the macroscopic shear thinning behavior.

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Section: Resultssupporting

confidence: 85%

Nanostructures and Viscosities of Nafion Dispersions in Water/Ethanol from Dilute to Concentrated Regimes

Gupit

Maekawa

et al. 2020

Macromolecules

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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%

“…A very complex, aging, dynamic, nonergodic arrested state and rich phase diagrams dependent on the nature of the polymer or surfactant additives were also observed. − Such behavior reflects the high shape anisotropy of disks and the presence of competing attractive and repulsive interactions between charged faces and edges.…”

Section: Introductionmentioning

confidence: 99%

“…Organization of Lap in aqueous suspensions significantly depends on the concentration of Lap particles, C l , the concentration of the ionic component, C i , and the time of gelling (aging), t g . In salt-free water conditions ( C i < 10 –4 M), the formation of sol (or separated sol and gel phases) at C l < 1% wt, equilibrium gel at 1% < C l < 2%, Wigner glass at 2% < C l < 3%, and nematic gel at C l > 3% was observed. − At relatively large concentrations ( C l = 2%), the particles are organized in “house-of-card” structures supported by edge-to-face contacts . The processes of structural aging (gelling or glass formation) may be rather long lasting and strongly depend upon the concentration of Lap .…”

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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“…Additional information, such as sample states and results obtained from other simultaneous measurements, is also recorded in the event-recording raw data. To take advantage of this method, we have developed various sample environments to investigate non-equilibrium systems using TAIKAN (Iwase, Ogura et al, 2018;Iwase et al, 2019).…”

Section: Instrument and Apparatusmentioning

confidence: 99%

New measurement system based on small-angle neutron scattering for structural analysis of light-responsive materials

Iwase¹,

Akamatsu²,

Inamura³

et al. 2023

J Appl Cryst

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With the increasing importance of light-responsive materials, it is vital to analyze the relationship between function and structural changes induced by light irradiation. Small-angle scattering (SAS) is effective for such structural analysis. However, quantitatively capturing local molecular structure formation and molecular reactions at a scale of less than 1 nm via SAS is difficult. In this study, to analyze the structure of non-equilibrium phenomena in light-responsive materials, a new sample environment has been developed for a time-of-flight small- and wide-angle neutron scattering instrument (TAIKAN), comprising a UV–Vis irradiation system, UV–Vis absorption measurement equipment and photodetector. Simultaneous measurement of small-angle neutron scattering and UV–Vis absorption was achieved. This system was used to demonstrate the in situ observation of UV–Vis irradiation-induced structural change of micelles formed by 4-butylazobenzene-4′-(oxyethyl)trimethylammonium bromide, which is a light-responsive surfactant, in an aqueous solution. The results showed that the present measuring system provides direct information on the interplay between changes in micelle structure and changes in molecular configuration.

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Structural investigation of hectorite aqueous suspensions by dielectric microscopy and small-angle neutron scattering coupling with rheological measurement

Cited by 18 publications

References 14 publications

Nanostructures and Viscosities of Nafion Dispersions in Water/Ethanol from Dilute to Concentrated Regimes

Nanostructures and Viscosities of Nafion Dispersions in Water/Ethanol from Dilute to Concentrated Regimes

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

New measurement system based on small-angle neutron scattering for structural analysis of light-responsive materials

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