Liquid Crystal Materials
“Liquid crystals(LCs) are a state of matter that have properties between those of a conventional liquid and those of a solid crystal. For instance, an LC may flow like a liquid, but its molecules may be oriented in a crystal-like way. There are many different types of LC phase, which can be distinguished by their different optical properties (such as birefringence). When viewed under a microscope using a polarized light source, different liquid crystal phases will appear to have distinct textures. The contrasting areas in the textures correspond to domains where the LC molecules are oriented in different directions. Within a domain, however, the molecules are well ordered. LC materials may not always be in an LC phase (just as water may turn into ice or steam).”
“Liquid crystals can be divided into thermotropic, lyotropic and metallotropic phases. Thermotropic and lyotropic LCs consist of organic molecules. Thermotropic LCs exhibit a phase transition into the LC phase as temperature is changed. Lyotropic LCs exhibit phase transitions as a function of both temperature and concentration of the LC molecules in a solvent (typically water). Metallotropic LCs are composed of both organic and inorganic molecules; their LC transition depends not only on temperature and concentration, but also on the inorganic-organic composition ratio.”
“Examples of liquid crystals can be found both in the natural world and in technological applications. Most modern electronic displays are liquid crystal based. Lyotropic liquid-crystalline phases are abundant in living systems. For example, many proteins and cell membranes are LCs. Other well-known LC examples are solutions of soap and various related detergents , as well as tobacco mosaic visus.”
(Wikipedia, Liquid Crystals, 3/6/2010).
Materials
Liquid Crystal Displays
Liquid Crystal Nanofibers
Liquid Crystal Shape Memory Materials
Recent Journal Articles
Molecular Weight-Induced Structural Transition of Liquid-Crystalline Polymer Semiconductor for High-Stability Organic Transistor
( 4442–4447)Advanced Functional Materials 21 #23 (2011)
Kim et al, South Korea and California, fabricated polymer field-effect transistors (PFETs) with high electrical stability under bias-stress, by minimizing the density of charge trapping sites caused by the disordered regions. Here we report PFETs with excellent electrical stability comparable to that of single-crystalline organic semiconductors by specifically controlling the molecular weight (MW) of the donor-acceptor type copolymer semiconductors, poly (didodecylquaterthiophene-alt-didodecylbithiazole). We found that MW-induced thermally structural transition from liquid-crystalline to semi-crystalline phases strongly affects the device performance (charge-carrier mobility and electrical bias-stability) as well as the nanostructures such as the molecular ordering and the morphological feature. This enhancement of the electrical bias-stability can be attributed to highly ordered liquid-crystalline nanostructure of copolymer semiconductors on dielectric surface via the optimization of molecular weights. (RDC 12/6/2011)
Review Articles
Drops and shells of liquid crystal
(345-359) Colloid and Polymer Science 289 #4 (2011)
Lopez-Leon and Fernandez-Nieves of the Georgia Institute of Technology, Georgia, review the state of the art concerning drops and shells of liquid crystal. We especially focus on the defect structures observed with liquid crystals with different degrees of order under different boundary conditions and on the transitions between these structures. (RDC 3/26/2011)