Carbon Nanotubes in Liquid Crystals: Fundamental Properties and Applications

Abstract

The structure and properties of liquid crystalline suspensions filled by carbon nanotubes (CNTs) are critically reviewed. Special attention is paid to interactions between CNTs and molecules of the liquid crystals (LC), which lead to formation of ordered supramolecular structures. These structures, in turn, determine unique physical properties of LC + CNT suspensions, including electrical conductivity, dielectric permittivity, phase transitions, optical transmission, memory effects that can be used in electrooptic and optoelectronic devices, etc. Great variety of LC phases are considered as a host media, such as nematics, cholesterics, smectics of different types (including ferroelectrics), lyotropic, chromonic, ionic and hydrogen-bonded liquid crystals. Alongside multi-and single-walled carbon nanotubes, the suspensions can also contain the platelets of organoclays used for facilitation of CNT dispersing. Recent practical applications of LC + CNT suspensions and nanomaterials based thereon are also outlined.

Nano-Objects and Ions in Liquid Crystals: Ion Trapping Effect and Related Phenomena

“…Since the well-developed surface (in other words, the high surface to volume ratio) and strong enough attractive interactions between the surface of the purifying agents and the ion are the two major factors affecting the trapping efficiency, nanoparticles known for their extremely high surface to volume ratio are promising candidates for the development of the ion capturing agents. Recent progress in the design of nanomaterials and their successful incorporation in liquid crystals [105][106][107][108][109][110][111][112][113][114][115][116][117] provides the foundation for considering nano-objects embedded in liquid crystals as ion capturing agents. We will discuss the property of nanoparticles to trap ions in the next section of this manuscript.…”

“…The intriguing properties of nanoparticles in liquid crystals are being actively studied in many laboratories around the globe, and we refer readers to review manuscripts available on this subject for more details [105][106][107][108][109][110][111][112][113][114][115][116][117]. In this section, we will analyze the existing literature from the perspective of the ion capturing phenomenon.…”

“…Effects of various carbon-based nanomaterials (fullerenes, graphene, carbon nanotubes, diamond nanoparticles, and carbon dots) on electrical properties of liquid crystals have been reported in numerous papers [105,116,. Table 2 provides a short summary of the reported effects.…”

“…Table 2 provides a short summary of the reported effects. As can be seen, both decrease [118,119,[121][122][123][124][125][126][127][143][144][145][146][147][148][149][150][151][152] and increase [105,120,[128][129][130][131][132][133][134][135][136][137][138][139][140][141][142][150][151][152][153] in the electrical conductivity of liquid crystals doped with carbon-based nanomaterials were reported.…”

“…The ion trapping by graphene nanomaterial was suggested to explain experimental results reported in [125,126]. The electrical properties of liquid crystals doped with carbon nanotubes (CNT) were explored in numerous papers [105,116,. The majority of these manuscripts [105,116,117,[128][129][130][131][132][133][134][135][136][137][138][139][140][141][142] report the enhancement of the electrical conductivity  of liquid crystals doped with carbon nanotubes.…”