Anionic-cationic surfactant mixture providing the electrically controlled homeotropic surface anchoring of liquid crystals

Abstract

4-heptyloxybenzoate benzyl dodecyldimethylammonium (HOBBDDA) is synthesized and its orienting influence on nematic liquid crystal 4-pentyl-4'-cyanobiphenyl (5CB) is tested. HOBBDDA dissolved up to 1.4 percent in 5CB droplets dispersed in polymer film does not change the tangential surface anchoring inherent to polyvinyl alcohol matrix used. Homeotropic surface anchoring is realized if the HOBBDDA content exceeds 1.7 percent. The molecules of the surfactant in 5CB dissociate into anions and cations. The anions modify the surface anchoring under the action of DC electric field both in the normal and inverse mode. The mixture of HOBBDDA and cetyltrimethylammonium bromide can function as a binary ioniccationic surfactant which significantly expands the prospects for using the ionic-surfactant method to control liquid crystal materials.

Optical Textures and Orientational Structures in Cholesteric Droplets with Conical Boundary Conditions

“…The configuration of director n (a unit vector oriented along the preferred orientation of the long axes of molecules), in turn, depends on the LC elastic constants, boundary conditions (preferred director orientation on the interface, LC anchoring energy), droplet's size and shape, applied electric (magnetic) field [1,[10][11][12]. The orientational structure and, consequently, the optical properties of such liquid crystal materials can be changed by modifying the boundary conditions [13][14][15][16][17], varying LC parameters or applying an electric field [1]. It makes it possible to use them in the electrically controlled shutters [18,19], sensors [20,21], lasers [22,23], polarizers [24,25], etc.…”

40.2: Anisotropic media in display technologies: Development and prospects of application

“…The proposed approach of design of new anisotropic materials, modeling of various processes are based on numerous data obtained in the last decades in the study of liquid crystals and ordered fluids; on the use of the anisotropy of the molecules of polyfunctional compounds for the design of new molecular structures (molecular engineering), films, liquid crystals [1][2][3], micelles, membranes, etc. and for the creation of anisotropic ensembles of molecules and systems.…”