materialsscienceandengineering:
Liquid Crystals: Intermediate phases of matter
The term liquid crystals may sound like an oxymoron, given that liquid matter consists of unaligned atoms or molecules in constant random motion while crystals are defined as solids whose atoms or molecules are arranged in a highly ordered microscopic structure, but this unique phase of matter is very real and quite relevant. Neither true liquids or crystals, liquid crystal phases of matter have many of the physical attributes of liquids but with a certain degree of order to its constituent molecules.
Liquid crystals were discovered in 1888 by an Austrian botanical physiologist who discovered that his cholesterol derivative appeared to have two melting points, first turning into a cloudy liquid at 145° C and then a transparent one at 178° C. However, it wasn’t until many decades later that scientists truly began to study liquid crystals with interest, including one French physicist Pierre-Gilles de Gennes who would eventually receive a Nobel Prize for his work.
Generally cloudy in appearance, liquid crystals exist in a variety of phases of their own (called mesophases). Two of these such phases are shown above, compared with conventional solid and liquid matter. The nematic (meaning thread like) phase of a liquid crystal consists of molecules all aligned in the same direction even as they are capable of drifting around as in any other liquid. The smectic (meaning soap like) phase consists of molecules arranged in layers that can slip over each other. Other liquid crystal phases include chiral phases, discotic phases, and bowlic phases.
The most common and perhaps well known use of liquid crystals is in liquid crystal displays, or LCDs, which rely on the changing optical properties of liquid crystals around electric fields.
Sources: ( 1 - images 2 + 3 ) ( 2 - image 1 ) ( 3 )
So important, but so weird.
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