Abstract:The presence of ions in liquid crystals is one of the grand challenges that hinder the application of liquid crystals in various devices, which include advanced 3-D and flexible displays, tunable lenses, etc. Not only do they compromise the overall performance of liquid crystal devices, ions are also responsible for slow response, image sticking, and image flickering, as well as many other negative effects. Even highly purified liquid crystal materials can get contaminated during the manufacturing process. Moreover, liquid crystals can degrade over time and generate ions. All of these factors raise the bar for their quality control, and increase the manufacturing cost of liquid crystal products. A decade of dedicated research has paved the way to the solution of the issues mentioned above through merging liquid crystals and nanotechnology. Nano-objects (guests) that are embedded in the liquid crystals (hosts) can trap ions, which decreases the ion concentration and electrical conductivity, and improves the electro-optical response of the host. In this paper, we (i) review recently published works reporting the effects of nanoscale dopants on the electrical properties of liquid crystals; and (ii) identify the most promising inorganic and organic nanomaterials suitable to capture ions in liquid crystals.

Nanoparticles embedded in liquid crystals can trap mobile ions and decrease their concentration. In this paper, we generalize the nanoparticles-based approach and, through the quantitative analysis, identify the ferroelectric micro- and nanomaterials as the most promising “ion traps” that ensure close to 100% liquid crystal purification. We demonstrate that the treatment of liquid crystals with ferroelectric materials leads to a two-order of magnitude decrease in their electrical conductivity. This value exceeds previous data reported for similar systems by a factor of 10. Ferroelectric nanoparticles, when dispersed and stabilized in liquid crystals, act as highly efficient permanent ion traps, solve the problem of uncontrolled ionic contaminations, and eliminate the negative effects caused by ions.

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