Abstract
We present the macroscopic dynamics of polar nematic liquid crystals in a two-fluid context. We investigate the case of a nonchiral as well as of a chiral solvent. In addition, we analyze how the incorporation of a strain field for polar nematic gels and elastomers in a solvent modifies the macroscopic dynamics. It turns out that the relative velocity between the polar subsystem and the solvent gives rise to a number of cross-coupling terms, reversible as well as irreversible, unknown from the other two-fluid systems considered so far. Possible experiments to study those novel dynamic cross-coupling terms are suggested. As examples we just mention that gradients of the relative velocity lead, in polar nematics to heat currents and in polar cholesterics to temporal changes of the polarization. In polar cholesterics, shear flows give rise to a temporal variation in the velocity difference perpendicular to the shear plane, and in polar nematic gels uniaxial stresses or strains generate temporal variations of the velocity difference.Graphical abstract
Highlights
There are many two-fluid systems composed of two immiscible subsystems including, as examples, fluid emulsions [1], colloidal suspensions [2], polymer solutions and mixtures [3], fiber networks in a matrix [4,5], polymeric materials reinforced by carbon nanotubes [6], and microtubules coupled to the cytoskeleton in cells [7]
Macroscopic dynamic two-fluid descriptions have been given for a number of soft matter materials and complex fluids starting with immiscible liquids [8,9] and combinations of ordinary or viscoelastic liquids with nematic liquid crystals [8]
We have predominantly analyzed the macroscopic dynamics of polar two-fluid systems: polar nematics and gels in a nonchiral as well as in a chiral solvent
Summary
There are many two-fluid systems composed of two immiscible subsystems including, as examples, fluid emulsions [1], colloidal suspensions [2], polymer solutions and mixtures [3], fiber networks in a matrix [4,5], polymeric materials reinforced by carbon nanotubes [6], and microtubules coupled to the cytoskeleton in cells [7]. Macroscopic dynamic two-fluid descriptions have been given for a number of soft matter materials and complex fluids starting with immiscible liquids [8,9] and combinations of ordinary or viscoelastic liquids with nematic liquid crystals [8]. This approach has been applied to a number of other two-fluid systems including immiscible compound materials in solids and gels [10], bioinspired complex fluids [11,12], and materials characterized by the formation of clusters, for example of smectic clusters above the nematic to smectic A transition [13] and of clusters above the glass transition [14]. 4, we analyze how for polar nematic gels and elastomers the elastic strain field can be incorporated in a two-fluid description involving a nonchiral as well as achiral solvent. Throughout the paper we comment which static and dynamic cross-coupling terms survive the transition from polar to nonpolar nematics or cholesterics
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