Polar in-plane surface orientation of a ferroelectric nematic liquid crystal: Polar monodomains and twisted state electro-optics

Xi Chen; Eva Korblova; Matthew A Glaser; Joseph E Maclennan; David M Walba; Noel A Clark

doi:10.1073/pnas.2104092118

Polar in-plane surface orientation of a ferroelectric nematic liquid crystal: Polar monodomains and twisted state electro-optics

Proc Natl Acad Sci U S A. 2021 Jun 1;118(22):e2104092118. doi: 10.1073/pnas.2104092118.

Authors

Xi Chen^{1

2}, Eva Korblova^{2

3}, Matthew A Glaser^{1

2}, Joseph E Maclennan^{1

2}, David M Walba^{2

3}, Noel A Clark^{4

2}

Affiliations

¹ Department of Physics, University of Colorado, Boulder, CO 80309.
² Soft Materials Research Center, University of Colorado, Boulder, CO 80309.
³ Department of Chemistry, University of Colorado, Boulder, CO 80309.
⁴ Department of Physics, University of Colorado, Boulder, CO 80309; noel.clark@colorado.edu.

Abstract

We show that surface interactions can vectorially structure the three-dimensional polarization field of a ferroelectric fluid. The contact between a ferroelectric nematic liquid crystal and a surface with in-plane polarity generates a preferred in-plane orientation of the polarization field at that interface. This is a route to the formation of fluid or glassy monodomains of high polarization without the need for electric field poling. For example, unidirectional buffing of polyimide films on planar surfaces to give quadrupolar in-plane anisotropy also induces macroscopic in-plane polar order at the surfaces, enabling the formation of a variety of azimuthal polar director structures in the cell interior, including uniform and twisted states. In a π-twist cell, obtained with antiparallel, unidirectional buffing on opposing surfaces, we demonstrate three distinct modes of ferroelectric nematic electro-optic response: intrinsic, viscosity-limited, field-induced molecular reorientation; field-induced motion of domain walls separating twisted states of opposite chirality; and propagation of polarization reorientation solitons from the cell plates to the cell center upon field reversal. Chirally doped ferroelectric nematics in antiparallel-rubbed cells produce Grandjean textures of helical twist that can be unwound via field-induced polar surface reorientation transitions. Fields required are in the 3-V/mm range, indicating an in-plane polar anchoring energy of w _P ∼3 × 10^-3 J/m².

Keywords: alignment; ferroelectric; liquid crystal; nematic; surface.