Abstract
Liquid crystals represent a fascinating intermediate state of matter, with dynamic yet organized molecular features and untapped opportunities in sensing. Several works report the use of liquid crystal droplets formed by microfluidics and stabilized by surfactants such as sodium dodecyl sulfate (SDS). In this work, we explore, for the first time, the potential of surface-active ionic liquids of the imidazolium family as surfactants to generate in high yield, stable and oriented liquid crystal droplets. Our results show that [C12MIM][Cl], in particular, yields stable, uniform and monodisperse droplets (diameter 74 ± 6 µm; PDI = 8%) with the liquid crystal in a radial configuration, even when compared with the standard SDS surfactant. These findings reveal an additional application for ionic liquids in the field of soft matter.
Highlights
Dynamic self-assembled architectures, as liquid crystal droplets, are extremely interesting systems to provide low energy transducers in sensing
Liquid crystals (LCs)-based sensors for chemical analytes have been used in two main formats: (i) LCs deposited onto chemically-modified solid interfaces and (ii) LCs in aqueous interfaces, namely LC droplets or thin films [4,6]
LC droplets have been mainly reported using surfactants, namely sodium dodecyl sulfate (SDS), that minimize the interfacial tension between the two phases— facilitating droplet generation and preventing coalescence—while simultaneously promoting LC director alignment
Summary
Dynamic self-assembled architectures, as liquid crystal droplets, are extremely interesting systems to provide low energy transducers in sensing. Liquid crystals (LCs) are a class of soft materials that blend long-range order and fluidity [1,2,3]. They possess many attractive properties, namely their sensitivity to external stimuli—e.g., electrical and magnetic fields, light, temperature, chemical analytes—that result in a change in their director profile [4,5]. LC ordering within droplets is a result of their anisotropic elasticity and surface anchoring properties. It is well known that the anchoring of LCs in contact with aqueous surfaces containing surfactants is strongly influenced by the structure of the hydrophobic aliphatic chain, its length and conformation
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