What is a lyotropic agent?

A liquid crystalline mesophase is called lyotropic (a portmanteau of lyo- “dissolve” and -tropic “change” ) if formed by dissolving an amphiphilic mesogen in a suitable solvent, under appropriate conditions of concentration, temperature and pressure.

What are the chemical properties of liquid crystals?

Liquid crystal materials generally have several common characteristics. Among these are a rod-like molecular structure, rigidness of the long axis, and strong dipoles and/or easily polarizable substituents.

What is Discotic liquid crystal?

Discotic liquid crystals are mesophases formed from disc-shaped molecules known as “discotic mesogens”. These phases are often also referred to as columnar phases. The charge transfer allows the discotic liquid crystals to be electrically semiconductive along the stacking direction.

Are liquid crystals toxic?

Liquid crystals comprise of about 10–25 compounds (Zhuang et al., 2012) whereas other studies claim that their toxicity is minimal (Tsydenova and Bengtsson, 2011). However, some companies try to eliminate the use of chlorine in LCD manufacturing with the aim of gaining potential environmental benefits.

How will you differentiate liquid crystals from pure liquids?

Liquids can flow, for example, while solids cannot, and crystalline solids possess special symmetry properties that liquids lack. Liquid crystals share with liquids the ability to flow but also display symmetries inherited from crystalline solids.

What is liquid crystal polarization?

Liquid crystals have the property of birefringence; i.e., the refractive index of the material depends on the propagation direction and the polarization of the light. In liquid crystals birefringence can be used to transform linearly polarized light to elliptically polarized light.

What is the main difference between liquids and liquid crystals?

A true liquid is isotropic , meaning that its properties are uniform in all directions— the result of its molecules being in constant random motion. Crystalline solids, in contrast, are anisotropic ; optical- and other properties such as thermal and electrical conductivity vary with direction.

Is Kevlar a Lyotropic?

For example, poly(p-phenylene terephthal- amide) (PPTA) which is the chemical structure of Kevlar® is a lyotropic LCP and exhibits outstanding mechanical properties, good thermal stability, and ex- cellent chemical resistance, but this polyamide fiber can only be spinned from its conc. H2SO4 solution.

Can lyotropic liquid crystalline surfactants provide sustained release drug delivery systems?

Lyotropic liquid crystalline phases formed from glycerate surfactants as sustained release drug delivery systems A new class of surfactants with glycerate headgroups, that form viscous lyotropic liquid crystalline phases in excess water, have been investigated for their potential to provide sustained release matrices for depot drug delivery.

What are lyotropic crystals made of?

Lyotropic liquid crystals are formed in mixtures of amphiphiles (e.g., surfactants) and solvents, for example, detergents and water. Consequently, these phases are thermodynamically stable at defined temperatures, pressures, and concentrations.

What is the difference between lyotropic and amphiphilic crystals?

On the other hand, a lyotropic liquid crystal is formed when, under certain circumstances of pressure, temperature and concentration, an amphiphilic molecule is melted in an appropriate solvent medium. The “lyotropic” liquid crystal mixture is controlled by varying the concentration of the solvent.

What is a surfactant in aqueous solution?

In aqueous solution, surfactants are known to form a lyotropic liquid crystal phase. For example, an aqueous solution of hexadecyltrimethyl ammonium bromide (C 16 TMABr), one type of surfactant, forms a liquid crystal phase that is hexagonal, cubic, or lamellar in structure, depending on the solution conditions.