Liquid Crystals

Abstract

Liquid crystals (LCs) represent a state of matter which is characterized by a unique combination of order and mobility on molecular, supramolecular and macroscopic levels. This is a true thermodynamic stable state of matter and has been recognized and accepted as the fourth state of matter after solid, liquid, and gas (1-18). They have developed from a mere scientific curiosity in the beginning to one of the foundations of mobile information technology devices today (19)(20)(21)(22)(23)(24)(25). LCs are presently common topics in academic books and also in our daily life. Terms such as LCD, ie, LC display, and Kevlar have become familiar consumer products. The unusual feature which makes this state of matter unique among the others is the combination of orientational (and, sometimes, positional) order and dynamics, giving rise to materials with anisotropic physical properties that are switchable under the influence of small external stimuli. LCs have been regarded as unique functional soft materials from both scientific and technological point of view. The unique combination of counterintuitive properties, ie, order and fluidity, is not only an essential requirement for living matter, but also it is the foundation of the numerous technological applications of LC materials. Simultaneous exhibition of order and dynamics is the basic principle for self-organization and structure formation in living systems. Accordingly, LCs play a crucial role in living systems and in biology (18). For example, no life would be possible without the ordered and dynamic self-assembly of lipids into bilayers within the cell membrane. Several biological molecules such as lipids, carbohydrates, proteins, and nucleic acids have been found to exist in various liquid crystalline phases (26-34). The appearance of mesomorphism in DNAs has been related to the significant role that LCs would have played in the evolution of biological information in the pre-biotic world (35-38). LCs self-assemble into various structures with the help of many different types of molecular interactions such as van der Waals, dipolar and quadrupolar interaction, charge transfer, p-p interaction, metal coordination, and hydrogen bonding. Thus, LCs can be considered as prototype supramolecular systems which furnish well-defined self-assembled architectures using noncovalent secondary interactions (39). Scientifically, the LC field is a fertile ground to study supramolecular self-assembly of matter and soft materials. Moreover, LCs persuasively demonstrate the powerful organization principle of matter by maximizing the interaction energy and minimizing the excluded volume.Overall, LCs have developed into a fascinating and prosperous field, reaching out into different areas of science by providing basic knowledge of the fundamental rules governing self-assembly from simple to complex modes. The domains of LCs span across multiple disciplines of pure and applied science including optics, materials science, bioscience, nanoscience etc. Their science and technology are tru...

Light-Driven Liquid Crystalline Materials: From Photo-Induced Phase Transitions and Property Modulations to Applications

“…Depending on how the mesophases can been attained, LCs are broadly classified into two different categories namely thermotropic and lyotropic LCs. , Thermotropic LC phases can be achieved either by heating a crystalline solid or by cooling an isotropic liquid. LC phase formation in organic materials made of anisometric molecules can be briefly outlined as follows.…”

Self-Organized 3D Photonic Superstructure: Blue Phase Liquid Crystal

“…Figure 9.13 outlines the structural change in terms of space group [95]. Under electrostriction, the crystal structure of BPII is distorted from cubic P4 2 [84] and Trebin et al [101] had modeled the lattice distortion of BPs from the theoretical aspects. Besides local reorientation, electrostriction often accompanies torque-induced irreversible crystal reorientation (cf.…”

Liquid Crystalline Anisotropic Nanoparticles: From Metallic and Semiconducting Nanoparticles to Carbon Nanomaterials

“…Lekkerkerker and coworkers reported the LC phase behavior of gibbsite (Al (OH) 3 ) platelets in a series of systematic studies [97][98][99][100]. Nematic, lamellar and columnar phase formations have been observed and characterized in gibbsite suspensions.…”

“…The constituents of the mesophases are known as mesogens. LCs have been regarded as unique functional soft materials from both scientific and technological point of view [1][2][3][4][5][6][7]. The counterintuitive combination of order and dynamics (fluidity) of the building blocks in this fascinating state of matter yields soft materials with anisotropic (direction dependent) properties that are extremely responsive under the influence of small external stimuli [8].…”