--- trunk/tengDissertation/LiquidCrystal.tex 2006/05/26 19:02:25 2780 +++ trunk/tengDissertation/LiquidCrystal.tex 2006/05/31 04:29:44 2781 @@ -1,7 +1,45 @@ \chapter{\label{chapt:liquidcrystal}LIQUID CRYSTAL} \section{\label{liquidCrystalSection:introduction}Introduction} +% liquid crystal +Long range orientational order is one of the most fundamental +properties of liquid crystal mesophases. This orientational +anisotropy of the macroscopic phases originates in the shape +anisotropy of the constituent molecules. Among these anisotropy +mesogens, rod-like (calamitic) and disk-like molecules have been +exploited in great detail in the last two decades. Typically, these +mesogens consist of a rigid aromatic core and one or more attached +aliphatic chains. For short chain molecules, only nematic phases, in +which positional order is limited or absent, can be observed, +because the entropy of mixing different parts of the mesogens is +paramount to the dispersion interaction. In contrast, formation of +the one dimension lamellar sematic phase in rod-like molecules with +sufficiently long aliphatic chains has been reported, as well as the +segregation phenomena in disk-like molecules. + +% banana shaped +Recently, the banana-shaped or bent-core liquid crystal have became +one of the most active research areas in mesogenic materials and +supramolecular chemistry. Unlike rods and disks, the polarity and +biaxiality of the banana-shaped molecules allow the molecules +organize into a variety of novel liquid crystalline phases which +show interesting material properties. Of particular interest is the +spontaneous formation of macroscopic chiral layers from achiral +banana-shaped molecules, where polar molecule orientational ordering +is shown within the layer plane as well as the tilted arrangement of +the molecules relative to the polar axis. As a consequence of +supramolecular chirality, the spontaneous polarization arises in +ferroelectric (FE) and antiferroelectic (AF) switching of smectic +liquid crystal phases, demonstrating some promising applications in +second-order nonlinear optical devices. + +The most widely investigated mesophase formed by banana-shaped +moleculed is the $\text{B}_2$ phase, which is also known as +$\text{SmCP}$. + +%Previous Theoretical Studies + \section{\label{liquidCrystalSection:model}Model} \section{\label{liquidCrystalSection:methods}Methods}