Ferroelectric nanoparticle/liquid-crystal colloids for display applications

Abstract

A non-synthetic approach to modify liquid crystals (LCs) by dispersing low concentrations of ferroelectric nanoparticles is reported. These dilute colloids are stable and appear similar to a pure LC. However, by changing the concentration and the type of ferroelectric particles, the physical properties of the LC materials can be tailored, including the nematic isotropic transition temperature (T NI ), the dielectric constants, the birefringence (∆n), elastic constants, and the threshold voltage. Specifically, doping low concentrations of BaTiO 3 nanoparticles (~1%) into a LC MLC-6609 increases T NI up to~40°C. This giant shift of T NI has never been previously reported and indicates strong interactions between the LC and ferroelectric nanoparticles on a molecular level. The doped LC also demonstrates significant enhancement in birefringence (by 10-30%), dielectric anisotropy (by~50%), and the elastic constant K 33 (by~20%). Ferroparticles act as molecular additives and modify the intrinsic properties of LC materials without time consuming and expensive chemical synthesis. The new LC materials are very attractive and suitable for use in displays, switchable lenses, beam steering, as well as other light-controlling devices.

Ferroelectric nanoparticles in low refractive index liquid crystals for strong electro-optic response

“…5,6 Another example of hybrid materials are the suspensions of ferroelectric nanoparticles 7 in nematic liquid crystals. Liquid crystals functionalized in this way show increased phase transition temperatures as well as dielectric and optical anisotropy 8 and have potential applications in, for example, displays 9 as well as for photorefractive systems. 10 In this study, we explored the impact of nanoparticles on liquid crystals most suitable for optoelectronic applications, namely, low refractive index liquid crystals.…”

Terahertz properties of liquid crystals doped with ferroelectric BaTiO3 nanoparticles

“…As the previous studies suggested [5,7], the change in the properties of the nanoparticles suspensions could be related to the ferroelectric nps affecting the order parameter of host LC material. Therefore, we decided to prepare ferroelectric suspensions with LC materials with simpler structure, but composed of compounds similar to LC 2020.…”

“…In [4,5] there is a detailed description of the preparation the nematic ferroelectric nps solutions. We used the suspensions nps1, nps2 and nps3 with two materials 6CHBT and 2020.…”

“…The doping of a nematic liquid crystal (LC) with a small amount (<1%) of ferroelectric nanoparticles (nps) can cause significant changes in their properties such as clearing temperature, threshold voltage, elastic constants, dielectric anisotropy and birefringence in visible range [1][2][3][4][5][6]. The alternative method for improving or changing such LCs properties is by using chemical synthesis, which is time-consuming and expensive.…”

Ordering of ferromagnetic nanoparticles in nematic liquid crystals

“…On the other hand, also non-elongated particles of dielectric, paramagnetic, super-paramagnetic, ferroelectric or ferromagnetic nature can be employed and dispersed isotropically within different liquid crystal phases [1,22,23]. These particles cannot exhibit a preferred directionality, but they can interact to form anisotropic clusters, exhibit chaining mediated via the interaction of defects formed in the vicinity of the inclusion [3], or form patterns under the application of external fields, like it was studied in this investigation.…”