Issue 10, 2020

Steady-state rheology and structure of soft hybrid mixtures of liquid crystals and magnetic nanoparticles

Abstract

Using non-equilibrium molecular dynamics simulations, we study the rheology of a model hybrid mixture of liquid crystals (LCs) and dipolar soft spheres (DSS) representing magnetic nanoparticles. The bulk isotropic LC–DSS mixture is sheared with different shear rates using Lees–Edwards periodic boundary conditions. The steady-state rheological properties and the effect of the shear on the microstructure of the mixture are studied for different strengths of the dipolar coupling, λ, among the DSS. We find that at large shear rates, the mixture shows a shear-thinning behavior for all considered values of λ. At low and intermediate values of λ, a crossover from Newtonian to non-Newtonian behavior is observed as the rate of applied shear is increased. In contrast, for large values of λ, such a crossover is not observed within the range of shear rates considered. Also, the extent of the non-Newtonian regime increases as λ is increased. These features can be understood via the shear-induced changes of the microstructure. In particular, the LCs display a shear-induced isotropic-to-nematic transition at large shear rates with a shear-rate dependent degree of nematic ordering. The DSS show a shear-induced nematic ordering only for large values of λ, where the particles self-assemble into chains. Moreover, at large λ and low shear rates, our simulations indicate that the DSS form ferromagnetic domains.

Graphical abstract: Steady-state rheology and structure of soft hybrid mixtures of liquid crystals and magnetic nanoparticles

Article information

Article type
Paper
Submitted
18 Oct 2019
Accepted
08 Feb 2020
First published
11 Feb 2020
This article is Open Access
Creative Commons BY license

Soft Matter, 2020,16, 2516-2527

Steady-state rheology and structure of soft hybrid mixtures of liquid crystals and magnetic nanoparticles

G. P. Shrivastav, N. H. Siboni and S. H. L. Klapp, Soft Matter, 2020, 16, 2516 DOI: 10.1039/C9SM02080B

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