Liquid-Crystalline Nematic Phase in Aqueous Suspensions of a Disk-Shaped Natural Beidellite Clay

Paineau, Erwan; Antonova, K.; Baravian, Christophe; Bihannic, Isabelle; Davidson, Patrick; Dozov, I.; Impéror‐Clerc, Marianne; Levitz, Pierre; Madsen, Anders; Meneau, Florian; Michot, Laurent J.

doi:10.1021/jp908326y

Cited by 129 publications

(204 citation statements)

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“…On increasing the concentration in water, this clay forms a birefringent nematic gel phase. 13 Under shear flow, for shear rates larger than 100 s -1 , the 2D SAXS patterns (figure 6) in the tangential geometry exhibit a strong anisotropy that is more and more pronounced upon increasing the shear rate up to 2000 s -1 . At the same time, in the radial geometry (figure 6), almost no anisotropy is observed.…”

Section: Doped Lamellar Phasesmentioning

confidence: 95%

RheoSAXS studies of anisotropic complex fluids under shear

Silva¹,

Petermann²,

Kasmi³

et al. 2010

J. Phys.: Conf. Ser.

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Cylindrical intermediates in a shearinduced lamellar-to-vesicle transition J. Zipfel, F. Nettesheim, P. Lindner et al.Rheo-SAXS investigation of shear-thinning behaviour of very anisometric repulsive disc-likeclay suspensions A M Philippe, C Baravian, M Imperor-Clerc et al. Abstract. We discuss the application of in-situ rheological small angle X-ray scattering experiments to the study of complex fluids under shear, implemented using custom Couette cylinder rheometers mounted on the SWING beamline of the SOLEIL Synchrotron. We discuss several applications of this technique to the study of phase transitions in nanoparticle doped liquid crystals and shear alignment of clay suspensions. The concurrent capture of rheological and scattering data provides vital information that relates macroscopic properties such as viscosity to the microstructure of the fluid. IntroductionThe study of complex fluids and of their rheological properties is an active area of research with a wide range of applications.1 The bulk macroscopic properties of complex fluids, such as rheological properties such as shear viscosity, for example, will often depend on the structure of the fluid on a microscopic level. Thus it is often convenient to combine various techniques in order to study macroscopic and microscopic properties at the same time. Investigations using small angle scattering techniques (SAS) (light, neutrons, X-rays) can be performed on such fluids directly under flow; this allows the simultaneous recording of rheological quantities (such as flow-curves and viscosity profiles) and structural information. In the case of strongly anisotropic fluids, small angle X-ray or neutron scattering (SAXS/SANS) experiments are particularly well suited to following orientation phenomena of structured fluids under flow. Using new rheological small-angle (Rheo-SAXS) instruments developed at the SWING SAXS beamline of the SOLEIL synchrotron, we present some examples of results demonstrating in detail the behaviour under shear of doped surfactant lamellar phases and colloidal clay suspensions.

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Section: Doped Lamellar Phasesmentioning

confidence: 95%

RheoSAXS studies of anisotropic complex fluids under shear

Silva¹,

Petermann²,

Kasmi³

et al. 2010

J. Phys.: Conf. Ser.

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“…[19][20][21][22] Moreover, it has been found that suspensions of sodium montmorillonite and similar clays exhibit a negative (anomalous) birefringence, 14,23,24 sparking interest in the phenomenon. The mentioned anomaly consists in the tendency of the particles to orient under some conditions with their major axis perpendicular to the external field, instead of parallel, as in "normal" EB.…”

Section: Introductionmentioning

confidence: 99%

Electric birefringence spectroscopy of montmorillonite particles

et al. 2016

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Electric birefringence (EB) of suspensions of anisotropic particles can be considered an electrokinetic phenomenon in a wide sense, as both liquid motions and polarization of the electrical double layer (EDL) of the particles participate in the process of particle orientation under the applied field. The EB spectrum can be exploited for obtaining information on the dimensions, average value and anisotropy of the surface conductivity of the particles, and concentration and Maxwell-Wagner polarization of the EDLs. It is thus a highly informative technique, applicable to non-spherical particles. In this paper, we investigate the birefringent response of plate-like montmorillonite particles as a function of the frequency and amplitude of the applied AC electric field, for different compositions (pH, ionic strength, particle concentration) of the suspensions. The transient electric birefringence (i.e., the decay of the refractive index anisotropy with time when the field is switched off) is used for estimating the average dimensions of the particle axes, by modeling it as an oblate spheroid. The obtained values are very similar to those deduced from electron microscopy determinations. The frequency spectra show a very distinct behaviour at low (on the order of a few Hz) and high (up to several MHz) frequencies: the α and Maxwell-Wagner-O'Konski relaxations, characteristic of EDLs, are detected at frequencies above 10 kHz, and they can be well explained using electrokinetic models for the polarization of EDLs. At low frequencies, in contrast, the birefringence changes to negative, an anomalous response meaning that the particles tend to orient with their symmetry axis parallel to the field. This anomaly is weaker at basic pHs, high ionic strengths and low concentrations. The results can be explained by considering the polydispersity of real samples: the fastest particles redistribute around the slowest ones, inducing a hydrodynamic torque opposite to that of the field, in close similarity with results previously described for mixtures of anisometric particles with small amounts of spherical nanoparticles.

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“…This effect was recently described in clay suspensions [47][48][49][50][51][52], in which the liquidcrystalline character is evidenced by polarised light microscopy and small-angle X-ray scattering. These experiments on clay-based gel samples reveal strong positional and orientation orders of the particles, proving unambiguously the nematic character of the clay mineral-rich gel.…”

Section: Discussionmentioning

confidence: 73%