Shear Orientation of a Micellar Hexagonal Liquid Crystalline Phase: A Rheo and Small Angle Light Scattering Study

Richtering, Walter; Laeuger, Joerg; Linemann, Reinhard

doi:10.1021/la00023a073

Cited by 35 publications

(22 citation statements)

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“…The SALS pattern changed during this jump of J(t), indicating that the sample became shear aligned on a larger length scale. 12 In SANS a constant degree of orientation was also reached after ca. 10 strain units.…”

Section: Resultsmentioning

confidence: 97%

Shear Orientation of Lyotropic Hexagonal Phases

et al. 1998

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The shear orientation of the hexagonal liquid crystal phase of nonionic surfactant/water mixtures was investigated by means of different techniques, namely, microscopy, small-angle light and neutron scattering, (SALS, SANS), birefringence, and nuclear magnetic resonance (NMR). On a microscopic length scale probed by NMR, SANS, and birefringence, the shear flow results in an alignment of rodlike micelles along the flow direction. The 10 plane was parallel to the shear plane. On a mesoscopic length scale, studied by microscopy and SALS, a stripe texture was observed. This is due to an undulation of the director which is on average aligned in flow direction. The corresponding SALS pattern shows a better orientation correlation perpendicular to the flow direction.

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Section: Resultsmentioning

confidence: 97%

Shear Orientation of Lyotropic Hexagonal Phases

et al. 1998

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“…The second reason concerns the nature of the surfactant systems that were examined. These were on one hand nonionic surfactants such as penta(ethylene glycol) monododecyl ether (C 12 E 5 ) [293,294,295,296,297], and on the other microemulsions in which the cylinders are swollen with an apolar solvent [298,299,300]. In terms of size, charge and microstructure, these systems are different from those discussed so far.…”

Section: Iv1 Introductionmentioning

confidence: 99%

Shear-Induced Transitions and Instabilities in Surfactant Wormlike Micelles

Lerouge

Berret

2009

Polymer Characterization

147

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In this review, we report recent developments on the shear-induced transitions and instabilities found in surfactant wormlike micelles. The survey focuses on the nonlinear shear rheology and covers a broad range of surfactant concentrations, from the dilute to the liquid-crystalline states and including the semidilute and concentrated regimes. Based on a systematic analysis of many surfactant systems, the present approach aims to identify the essential features of the transitions. It is suggested that these features define classes of behaviors. The review describes three types of transitions and/or instabilities: the shear-thickening found in the dilute regime, the shear-banding which is linked in some systems to the isotropic-tonematic transition, and the flow-aligning and tumbling instabilities characteristic of nematic structures. In these three classes of behaviors, the shear-induced transitions are the result of a coupling between the internal structure of the fluid and the flow, resulting in a new mesoscopic organization under shear. This survey finally highlights the potential use of wormlike micelles as model systems for complex fluids and for applications.

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“…Above the intersection point, elastic properties dominate viscous properties and the liquid crystal behaves like a weak solid. This viscoelastic behavior is usual for hexagonal liquid crystals [28,29] and some authors have explained it using generalized Maxwell model [30]. On the contrary to lamellar phase, a finite structural relaxation time can be defined for this liquid crystal.…”

Section: Rheological Study Of Liquid Crystalsmentioning

confidence: 95%