Difference between revisions of "History of Liquid Crystals"
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=== What is a liquid crystal? === | |||
[[Image:Lc_phasechange.png|thumb|300px|]] | |||
Liquid crystals are anisotropic materials. This is important for their function in LC displays. | |||
In a crystal there is periodicity of a lattice in all three directions. In a liquid there is neither orientational or positional order. | |||
A liquid crystal phase or mesomorphic phase is a phase comprising molecules having a higher degree of orientational order than is found in a liquid and less positional order than is found in a crystal. Under certain conditions they can flow. | |||
There are many classes of liquid crystals having differing degrees of order. We need to ask if a molecule is capable of being liquid cyrstalline under certain conditions. Some molecules can be crystalline, liquid crystalline (and exist in different phases of liquid crystalline) and isotropic, depending on the conditions. | |||
<br clear='all'> | |||
[[Image:MBBA.png|thumb|300px|]] | |||
As shown in the diagram to the right there are discrete phase transitions between the crystal phase, the LC phase and the liquid phase. At each phase transition there is a corresponding heat of enthalpy for the transition. Much of the research in this area is german, as a result the letter K is often used to denote the cyrstalline phase (krystal in german). Nematic refers to the liquid cyrstalline phase (abbreviated N). Liquid phase may be abbreviated as l or I (for isotropic). Under the arrrow is temperature at which there is a phase transition. These transitions are usually quite sharp. | |||
[[category:liquid crystals]] | [[category:liquid crystals]] | ||
Revision as of 15:20, 24 June 2009
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What is a liquid crystal?
Liquid crystals are anisotropic materials. This is important for their function in LC displays.
In a crystal there is periodicity of a lattice in all three directions. In a liquid there is neither orientational or positional order.
A liquid crystal phase or mesomorphic phase is a phase comprising molecules having a higher degree of orientational order than is found in a liquid and less positional order than is found in a crystal. Under certain conditions they can flow.
There are many classes of liquid crystals having differing degrees of order. We need to ask if a molecule is capable of being liquid cyrstalline under certain conditions. Some molecules can be crystalline, liquid crystalline (and exist in different phases of liquid crystalline) and isotropic, depending on the conditions.
As shown in the diagram to the right there are discrete phase transitions between the crystal phase, the LC phase and the liquid phase. At each phase transition there is a corresponding heat of enthalpy for the transition. Much of the research in this area is german, as a result the letter K is often used to denote the cyrstalline phase (krystal in german). Nematic refers to the liquid cyrstalline phase (abbreviated N). Liquid phase may be abbreviated as l or I (for isotropic). Under the arrrow is temperature at which there is a phase transition. These transitions are usually quite sharp.
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