What are typical applications of liquid crystals?
Click to see answer
LCD displays, dyes (cholesterics), advanced materials (Kevlar), membranes, temperature measurement (by changing colours), solvents for GC, NMR, reactions, and drug delivery.
Click to see question
What are typical applications of liquid crystals?
LCD displays, dyes (cholesterics), advanced materials (Kevlar), membranes, temperature measurement (by changing colours), solvents for GC, NMR, reactions, and drug delivery.
What are the common states of matter?
Solid, liquid, and gas.
What is the preferred direction in a nematic liquid crystal called?
The preferred direction is known as the director.
What happens to the material at the highest temperatures in terms of its state?
At the highest temperatures, the material becomes an isotropic liquid.
What type of order do the constituents of liquid crystals possess?
They possess long-range orientational order, but not positional order.
What happens to the order in a crystal when it melts to form a liquid?
For many substances, both types of order (positional and orientational) are destroyed simultaneously when the crystal melts.
How can condensed matter be classified?
Condensed matter can be classified on the basis of order.
What unique properties do liquid crystals have?
They possess properties not found in either liquids or solids and may respond to external perturbations, changing color with temperature.
What causes the transition from crystalline solids to liquid crystals?
A change of temperature, which gives rise to thermotropic liquid crystals.
What happens to positional order when a crystal melts to form a smectic liquid crystal?
Not all positional order is destroyed.
What are the main properties of liquid crystals?
Liquid crystals exhibit properties between those of liquids and solid crystals, such as fluidity and the ability to flow while maintaining a degree of order.
What defines the smectic phase of liquid crystals?
The smectic phase features layers of molecules that have both positional and orientational order.
Can matter exist in states other than solid, liquid, and gas?
Yes, matter can exist in other states.
What phase do molecules enter after the smectic A phase when temperature increases?
The molecules enter the nematic phase.
Are liquid crystals actually crystals?
No, despite the name, liquid crystals are not crystals and need not be liquids.
What characteristics do molecules need to have to likely form a liquid crystal phase?
They should be elongated and have some degree of rigidity.
How do liquid crystals differ from regular crystals during melting?
For some substances, the orders are destroyed in stages, leading to the formation of liquid crystals.
What characterizes thermotropic liquid crystals?
Thermotropic liquid crystals change their phase in response to temperature variations.
What are NIOSOMES?
NIOSOMES are non-ionic surfactant-based vesicles used for drug delivery and other applications.
What type of liquid crystal has a phase transition that depends on temperature?
Thermotropic liquid crystals, which include Nematic, Smectic, and Cholesteric phases.
What is a state that occurs between a solid and a liquid?
Liquid crystals possess properties characteristic of both liquids and crystalline solids.
What did Friedrich Reinitzer observe about cholesterol benzoate in 1888?
He noted that it had two melting points: it melts at 145.5 °C forming a turbid liquid and becomes completely clear at about 178.5 °C.
In what applications are nematic liquid crystals widely used?
Nematic liquid crystals are widely used in electro-optic display devices.
What are some applications of liquid crystals?
Liquid crystals are widely used in displays, sensors, and optical devices due to their unique properties.
What are typical chemical structures associated with liquid crystals?
Cholesterol ester, phenyl benzoates, surfactants (like polyethylene oxides, alkali soaps, ammonium salts, lecithin), paraffins, glycolipids, and cellulose derivatives.
What is a characteristic of liquid crystals?
Liquid crystals are characterized by long-range orientational order but not positional order.
What is the first liquid crystal observed through a polarising microscope?
Cholesteryl benzoate.
Who verified Friedrich Reinitzer's observations on liquid crystals?
Physicist Otto Lehmann verified Reinitzer's observations.
What are some potential uses of cholesteric liquid crystals?
Sensors, thermometers, fashion fabrics that change colour with temperature, and display devices.
What roles do liquid crystals play in our bodies?
In our bodies, liquid crystals transport fats, make up cell membranes, and affect the functioning of hair cells in the inner ear and even DNA.
What is unique about cholesteric liquid crystals?
Cholesteric liquid crystals have a helical structure, which can affect their optical properties.
What is the characteristic order in the CHOLESTERIC phase?
In the CHOLESTERIC phase, there is orientational order and no positional order, with the director in helical order.
What is the first liquid crystal phase characterized by a layer-like arrangement and molecular motion?
The first liquid crystal phase is the smectic A.
What optical property do liquid crystals exhibit?
They are optically birefringent, having different indices of refraction associated with different crystallographic directions.
At what temperature does cholesteryl benzoate become isotropic?
186°C.
Why are chiral smectic C liquid crystals useful?
They are useful in LCDs.
What is the simplest form of liquid crystal?
The simplest form is a nematic liquid crystal.
What allows liquid crystals to flow like a liquid?
The loss of positional order.
At what temperature does cholesteryl benzoate exhibit liquid crystal properties?
147°C.
What term did Otto Lehmann introduce in 1890 regarding liquid crystals?
He introduced the term 'crystalline liquid'.
Where can liquid crystals be found in everyday life?
Liquid crystals are found in high-strength plastics, snail slime, laundry detergent, textile fibers like silk and Kevlar, crude oil, insect wings, mineral slurries, lipstick, Bose-Einstein condensates, and the mantles of neutron stars.
What is the nematic phase of liquid crystals?
In the nematic phase, the molecules are oriented in the same direction but do not have positional order.
What type of liquid crystal's phase transition depends on both temperature and concentration?
Lyotropic liquid crystals.
Who is credited with the actual discovery of liquid crystals?
The Austrian botanist Friedrich Reinitzer is credited with the discovery of liquid crystals.
What types of order can exist in the nematic phase?
In the nematic phase, it is possible to have both microscopic order and macroscopic order.
What is a crystal?
A crystal is a highly ordered structure which possesses long-range positional and orientational order.
How do we consume liquid crystals?
We consume liquid crystals as aligned molecules in gluten and as phospholipids in milk, where they stabilize fat globules.
What type of order is present in a nematic liquid crystal?
Nematic liquid crystals have long-range orientational order but no positional order.
How can the structure of the nematic phase be altered?
The structure of the nematic phase can be altered by applying an electric or magnetic field or by treating the surfaces of the sample container.
How do molecules align in the smectic phase?
Molecules align themselves approximately parallel and tend to arrange in layers.
What is an example of a rod-shaped molecule in liquid crystals?
Pentyl cyanobiphenyl is an example of a rod-shaped molecule.
What are the different types of liquid crystals?
The main types of liquid crystals include thermotropic, nematic, smectic, cholesteric, and lyotropic.
What are lyotropic liquid crystals?
Lyotropic liquid crystals form in response to changes in concentration of the solvent, typically in surfactant solutions.
What characterizes the nematic phase in terms of order?
The nematic phase has a high degree of orientational order but lacks macroscopic order, meaning orientation within a group is similar but varies between groups.
What occurs at temperatures below the nematic or cholesteric phase?
The smectic phase occurs.
What shape do many liquid crystal molecules have?
Many liquid crystals consist of elongated molecules.
Why do rod-shaped molecules like pentyl cyanobiphenyl tend to line up in parallel?
They line up in parallel for entropic as well as energetic reasons.