Introduction• Very Important in the study of Optics,Chemistry and Polymer Science.• Friedrich Reinitzer, australian chemist studiedabout it first in 1888• At present it is applied in many products inour society and has come in our daily Use.
Nematic Phase• Molecules in thisphase are long androd-like in shape. Theyare free to move inspace.
Chiral Nematic• This phase iscomposed of nematicmolecules in a helicalstructure about thelayer normal.• The distance that ittakes for themolecules to completeone turn is called thepitch.λ = n*p*cosθ
Smectic Phase• This phase can bereached at lowertemperatures than thenematic phase.• Molecules alignthemselves inlayers.(They arerestricted to theirplane.)• More order andhigher viscosity
Columnar Phase• Characterized by its stacked columns of molecules.• Discovered in 1977 by Chandrasekhar
Twisted Nematic• This is called thetwisted nematic liquidcrystal and thespacing between theplanes change withtemperature. Thespacing is associatedwith the wavelengthsof light.
Applications of Liquid CrystalsThe World Of Liquid Crystal
Liquid Crystal DisplaysLiquid crystal display (LCD) is a flat electronic display panel used as avisual display aid. It uses liquid crystals to create visual effects on screen.Liquid crystal is a state of matter between solids and liquids. LCDs do notgenerate light on their own but rely on sunlight or room light togenerate images with help of liquid crystal.
Advantages Of LCD• Brightness: Produces very bright images due to high peak intensity.Very suitable for environments that are brightly lit.• Emissions: Produce considerably lower electric, magnetic andelectromagnetic fields than CRTs.• Geometric Distortion : Geometric distortion at the nativeresolutions. Minor distortion can occur for other resolutions.• Power Consumption:Energy efficient. Consume less than 1/3 thepower of a comparable CRT. Consume less electricity than a CRT andproduce little heat.• Physical Aspects:Take up about 40% less desk space. LCDs are thinand compact.• Screen Shape :Completely flat screen.• Sharpness:At the native resolution, the image is perfectlysharp. Adjustments are required at all other resolutionswhich can result in measurable degradation to the image.
Liquid Crystal ThermometersLiquid-crystal thermometers use liquid crystals that change color inresponse to temperature changes. Mixtures of liquid crystals areenclosed in separate partitions. Numbers on the partitions indicatetemperatures according to the amount of heat present. Liquid-crystalthermometers include some indoor digital thermometers and feverthermometers, which are placed on the forehead.
Optical Imaging• Optical Imaging is an emerging technology with great potential forimproving disease prevention, diagnosis, and treatment in themedical office, at the bedside, or in the operating room
Helmets and Bullet-proof vests• Long-chained rigid polymers that orient parallel to each other, withvery strong inter-molecular interactions, strong enough to withstandthe impact of bullets.
Battery testing strips (used by DuraCell)• Charge indicator for batteries. The principles for this application issimilar to that used by liquid crystalline thermometers. Electricalcurrent passing through the media generates heat. The change ofrelative orientation of the layers produce a color change.
Slugs and Snails (nature)• Nature beat us to the punch in making use of liquid crystals. Themucus secreted by slugs behaves like liquid crystals. Its rod-shapedmolecules align in varying degrees to control the viscosity of themucus to adapt to different ground conditions.• Liquid crystals can also be found in biological cell-membranes
Conclusion• We know today that many chemical compounds canexist in the liquid crystal state, such as cholesterylbenzoate. Thanks to the scientists that worked sodiligently toward understanding this phenomenon,the world can focus on ways to make this productuseful in society. Over the last century manyapplications such as the detection of hot points inmicrocircuits, the findings of fractures or tumors inhumans and the conversion of infared images havebecome accessible due to the understanding of pitchin a liquid crystal.