Electric and magnetic fields in photoalignment of liquid crystals

Abstract

-The results of investigation of slow surface dynamics (easy axis gliding), induced by secondary illumination of photoaligned substrates with linearly polarized UV or blue light in the presence of electric (magnetic) fields, are presented for the first time. The initial surface orientation of nematic liquid crystal (NLC) was provided, in accordance with the standard photoalignment technique, via preliminary UV treatment of the glass substrates coated by sulfonic azo-dye SD1 film. The experiments fulfilled for the two geometries, A and B, corresponding to the normal (A) and parallel (B) orientation of fields relatively to liquid crystal (LC) layer, revealed different effects induced by electric (magnetic) fields. For geometry A, strong electric field applied, in combination with a linearly polarized blue light, to the planar layer in a sandwich-like LC cell with two photoaligned substrates results in simultaneous reorientation of easy axis on both substrates. It demonstrates the possibility of an azimuthal rotation of monodomain planar samples of LCs. For geometry B, usage of "in-plane" electric (magnetic) fields in the cell, composed of photoaligned and rubbed substrates, speeds up reorientation process of NLC easy axis respectively to pure light-induced reorientation. It provides electric control of operating times in previously proposed optical rewritable technology.

Fullerene-doped polyimide materials treated via the vacuum ultraviolet irradiation: Novel possible approach to create the structured relief

“…The introduction of the different nanoparticles (fullerenes, carbon nanotubes, quantum dots, reduced graphene oxides, etc.) is considered both inside the LC mesophase to affect the orientation of the LC dipoles, and at the interface of the solid substrate-LC interface to lay the LC molecules in a certain directions [1][2][3][4][5][6][7][8][9][10][11][12][13] . It permits to develop the LC devises in the twist-nematic, IPS-switching, MVA, etc.…”