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Orientation selection in lamellar phases by oscillatory shears

Zhi-Feng Huang·Jorge Vinals
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Abstract

In order to address the selection mechanism that is responsible for the unique lamellar orientation observed in block copolymers under oscillatory shears, we use a constitutive law for the dissipative part of the stress tensor that respects the uniaxial symmetry of a lamellar phase. An interface separating two domains oriented parallel and perpendicular to the shear is shown to be hydrodynamically unstable, a situation analogous to the thin layer instability of stratified fluids under shear. The resulting secondary flows break the degeneracy between parallel and perpendicular lamellar orientation, leading to a preferred perpendicular orientation in certain ranges of parameters of the polymer and of the shear.

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Zhi-Feng Huang, Jorge Vinals. 2006-01-17. Orientation selection in lamellar phases by oscillatory shears. https://doi.org/10.1103/physreve.73.060501

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