Transformation between elastic dipoles, quadrupoles, octupoles, and hexadecapoles driven by surfactant self-assembly in nematic emulsion

Abstract

Emulsions comprising isotropic fluid drops within a nematic host are of interest for applications ranging from biodetection to smart windows, which rely on changes of molecular alignment structures around the drops in response to chemical, thermal, electric, and other stimuli. We show that absorption or desorption of trace amounts of common surfactants can drive continuous transformations of elastic multipoles induced by the droplets within the uniformly aligned nematic host. Out-of-equilibrium dynamics of director structures emerge from a controlled self-assembly or desorption of different surfactants at the drop-nematic interfaces, with ensuing forward and reverse transformations between elastic dipoles, quadrupoles, octupoles, and hexadecapoles. We characterize intertransformations of droplet-induced surface and bulk defects, probe elastic pair interactions, and discuss emergent prospects for fundamental science and applications of the reconfigurable nematic emulsions.

Design and Preparation of Nematic Colloidal Particles

“…(d) Schematics showing the mechanism of the anchoring transition at the LC–glycerol droplet interface. Adapted with permission from ref . Copyright 2021 American Association for the Advancement of Science.…”

“…Colloidal and liquid crystalline systems are classic examples of soft condensed matter, exhibiting structural similarities with the forms of self-organization found in both living organisms and in solid-state materials. , Nematic liquid crystals (LCs) are fluids having anisotropic properties stemming from the spontaneous, long-range orientational order of their constituent anisotropic molecules . Their utility in electro-optic devices, such as LC displays, arises from their large birefringence and strong coupling to external fields and confining surfaces. , The use of nematic LCs as fluid hosts for colloidal dispersions enriches colloidal behavior due to anisotropic molecular interactions at colloidal surfaces and particle-induced defects and elastic distortions of the LC order. − Molecular interactions of rod-like LC molecules at the interface of another material result in energetically preferred alignment directions of the molecules at that interface. − Known as surface anchoring, this anisotropic interaction at LC surfaces defines surface boundary conditions and plays a key role in electro-optic applications involving LCs and in nematic colloidal self-assembly. − Surface anchoring , is one of the most important properties of LCs because of its relevance in practical applications. For instance, chemically and topographically patterned surfaces , have provided promising avenues for LC applications in displays, chemical sensing, biodetection, colloidal self-assembly, − …”

“…12 Intrinsically, as described above, pure silicon oil and glycerol droplets impose, respectively, homeotropic and tangential LC alignment at their interface inducing in a LC so-called elastic dipoles (Figures 1f and 2cviii) and quadrupoles (Figure 2ci and 2cv). 8,25 However, one can also modify and control the boundary conditions at the surface of fluid droplets by mixing specific additives like in ref 46. Spherical micrometer-size droplets of isotropic fluid in the bulk of a nematic LC can be obtained by mixing a small amount (∼1−5 vol %) of glycerol with a nematic LC and vigorous agitation such as flicking or sonication.…”

Stable O/W emulsions and oleogels with amphiphilic konjac glucomannan network: preparation, characterization, and application

“…Emulsions play a key role in many industrial products, including cosmetics, toiletries, cleaning agents, paints, and various food products. 1 Emulsions also provide functions of lubrication, 2 moisturizing, 3 monoclonal separation, 4 and protection of active components. 5 Emulsions are mixed systems composed of a dispersed phase and a continuous phase; the partition between the two phases is called the interface.…”

“…Emulsions play a key role in many industrial products, including cosmetics, toiletries, cleaning agents, paints, and various food products 1 . Emulsions also provide functions of lubrication, 2 moisturizing, 3 monoclonal separation, 4 and protection of active components 5 .…”