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Issue 14, 2012
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Rheology of lamellar liquid crystals in two and three dimensions: a simulation study

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Abstract

We present large scale computer simulations of the nonlinear bulk rheology of lamellar phases (smectic liquid crystals) at moderate to large values of the shear rate (Peclet numbers 10–100), in both two and three dimensions. In two dimensions we find that modest shear rates align the system and stabilise an almost regular lamellar phase, but high shear rates induce the nucleation and proliferation of defects, which in steady state is balanced by the annihilation of defects of opposite sign. The shear rate [small gamma, Greek, dot above]c at onset of this second regime is controlled by thermodynamic and kinetic parameters; we offer a scaling analysis that relates [small gamma, Greek, dot above]c to a critical “capillary number” involving those variables. Within the defect proliferation regime, the defects may be partially annealed by slowly decreasing the applied shear rate; this causes marked memory effects, and history-dependent rheology. Simulations in three dimensions show instead shear-induced ordering even at the highest shear rates studied here. This suggests that [small gamma, Greek, dot above]c shifts markedly upward on increasing dimensionality. This may in part reflect the reduced constraints on defect motion, allowing them to find and annihilate each other more easily. Residual edge defects in the 3D aligned state mostly point along the flow velocity, an orientation impossible in two dimensions.

Graphical abstract: Rheology of lamellar liquid crystals in two and three dimensions: a simulation study

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Article information


Submitted
14 Dec 2011
Accepted
14 Feb 2012
First published
24 Feb 2012

Soft Matter, 2012,8, 3817-3831
Article type
Paper

Rheology of lamellar liquid crystals in two and three dimensions: a simulation study

O. Henrich, K. Stratford, D. Marenduzzo, P. V. Coveney and M. E. Cates, Soft Matter, 2012, 8, 3817
DOI: 10.1039/C2SM07374A

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