Layered Systems Under Shear Flow

Svenšek, Daniel; Brand, Helmut R.

doi:10.1007/12_2009_37

Cited by 2 publications

(1 citation statement)

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“…Shear-induced changes in the structure of soft matter systems have been of great interest for many decades. − A particular example is lyotropic lamellar systems that exhibit rich phase behavior in both the static and dynamic range. − For these systems, a continuous application of shear can induce the formation of a defect structure consisting of multilamellar vesicles (MLVs) from the original lamellar L α phase consisting of extended stacks of parallel surfactant bilayers. , These MLVs consist of a hierarchy of many concentric spherical bilayer shells and are thus often referred to as “onions”. The potential of encapsulating certain substances in this geometry makes them an interesting medium for drug delivery in pharmaceutical applications or for microreactors. − Therefore, a thorough understanding of the MLV formation process in this nonequilibrium transition is vital with respect to usage on an industrial scale.…”

Section: Introductionmentioning

confidence: 99%

Multilamellar Vesicle Formation Probed by Rheo-NMR and Rheo-SALS under Large Amplitude Oscillatory Shear

et al. 2018

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The formation of multilamellar vesicles (MLVs) in the lyotropic lamellar phase of the system triethylene glycol mono n-decyl ether (CE)/water is investigated under large amplitude oscillatory shear (LAOS) using spatially resolved rheo-NMR spectroscopy and a combination of rheo-small angle light scattering (rheo-SALS) and conventional rheology. Recent advances in rheo-NMR hardware development facilitated the application of LAOS deformations in high-field NMR magnets. For the range of investigated strain amplitudes (10-50) and frequencies (1 and 2 rad s), MLV formation is observed in all NMR and most SALS experiments. It is found that the MLV size depends on the applied frequency in contrast to previous steady shear experiments where the shear rate is the controlling parameter. The onset of MLV formation, however, is found to vary with the shear amplitude. The LAOS measurements bear no indication of the intermediate structures resembling aligned multilamellar cylinders observed in steady shear experiments. Lissajous curves of stress vs strain reveal a transition from a viscoelastic solid material to a pseudoplastic material.

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Section: Introductionmentioning

confidence: 99%

Multilamellar Vesicle Formation Probed by Rheo-NMR and Rheo-SALS under Large Amplitude Oscillatory Shear

et al. 2018

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Non-Newtonian Rheology in Twist–Bend Nematic Liquid Crystals

Kats

2022

Jetp Lett.

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In this work we present a simple qualitative model to describe shear rheological behavior of the twist-bend nematic liquid crystals (NT B ). We find that at relatively low shear rate ( γ ≤ γc1) the stress tensor σ created by this shear strain, scales as σ ∝ γ1/2 . Thus the effective viscosity decreases with the shear rate (η ∝ γ−1/2 ) manifesting so-called shear-thinning phenomenon. At intermediate shear rate γc1 ≤ γ ≤ γc2, σ is almost independent of γ (a sort of plateau), and at large shear rate ( γ ≥ γc2), σ ∝ γ, and it looks like as Newtonian rheology. Within our theory the critical values of the shear rate scales as γc1 ∝ (η 0 2 /η 0 3 ) 2 , and γc2 ∝ (η 0 2 /η 0 3 ) 4 respectively. Here η0 2 and η0 3 are bare coarse grained shear viscosity coefficients of the effective smectics equivalent to the NT B phase at large scales. The results of our work are in the agreement with recent experimental studies.

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Layered Systems Under Shear Flow

Cited by 2 publications

References 61 publications

Multilamellar Vesicle Formation Probed by Rheo-NMR and Rheo-SALS under Large Amplitude Oscillatory Shear

Multilamellar Vesicle Formation Probed by Rheo-NMR and Rheo-SALS under Large Amplitude Oscillatory Shear

Non-Newtonian Rheology in Twist–Bend Nematic Liquid Crystals

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