Dimensional stability, liquid crystal

Liquid crystal polymers (LCP) are a recent arrival on the plastics materials scene. They have outstanding dimensional stability, high strength, stiffness, toughness and chemical resistance all combined with ease of processing. LCPs are based on thermoplastic aromatic polyesters and they have a highly ordered structure even in the molten state. When these materials are subjected to stress the molecular chains slide over one another but the ordered structure is retained. It is the retention of the highly crystalline structure which imparts the exceptional properties to LCPs. 

Polymerization of LB films, or deposition of LB films on polymers, offers the opportunity to impart to LB films a higher degree of mechanical integrity. However, preliminary work in this direction shows a conflict between the chainlike primary structure of the polymer and the well-organized supramo-lecular structure [15]. One possible solution may be the insertion of flexible spacers between the main chain polymer and the side chain amphiphile, a route also employed in liquid crystal polymers. These materials belong to an interesting class of two-dimensional polymers, of which there are few examples. These toughening techniques may eventually be applied to stabilize other self-assembled microstructures, such as vesicles, membranes, and microemulsions. 

For the design of ferrocene-based liquid crystals, the main structural feature that has to be taken into account is the three-dimensional structure of Fc. Interestingly, depending on the groups that are located on Fc, the latter unit can either reduce or enhance the stability of the liquid-crystalline state (see below). 

Wu, Y., Yuan, B., Zhao, J.-G. Ozaki, Y. (2003). Hybrid Two-Dimensional Correlation and Parallel Factor Studies on the Switching Dynamics of a Surface-stabilized Ferroelectric Liquid Crystal. Journal of Physical Chemistry B, Vol. 107, No. 31, pp. 7706-7715... 

Liquid crystal polymers (LCP) provide excellent strength, stiffness, dimensional stability and creep resistance. They are not damaged by the high temperatures commonly... 

J.Y. Huang, L.S. Li, and M.C. Chen, Probing molecular binding effect from zinc oxide nanocrystal doping in surface-stabilized ferroelectric liquid crystal with two-dimensional infrared correlation technique, J. Phys. Chem. C, 112, 5410-5415 (2008). 

The section commences with monosubstituted ferrocene derivatives, after which the influence of the substitution pattern on the formation and stability of liquid-crystalline phases for disub-stituted ferrocene derivatives will be discussed. Next, the influence of the three-dimensional structure of ferrocene on the mesomorphic properties will be highlighted, optically active ferrocene materials will be described and, finally, ferrocene-containing liquid-crystalline dendrimers will be introduced ferrocene-containing liquid-crystalline polymers will not be reported. Note that a review devoted to ferrocene-containing thermotropic liquid crystals has already been published. ... 

In Section 5.7.2 we discussed a general problem of stability of one, two- and three-dimensional phases. Here, we shall analyze stability of the smectic A liquid crystal, which is three-dimensional structure with one-dimensional periodicity. The question of stability is tightly related to the elastic properties of the smectic A phase. Consider a stack of smectic layers (each of thickness Z) with their normal along the z-direction. The size of the sample along z is L, along x and y it is L, the volume is V = Lj L. Fluctuations of layer displacement u(r) = u(z, r i) along z and in bofli directions perpendicular to z can be expanded in the Fourier series with wavevec-tors q and q (normal modes) ... 

Liquid crystal polymers offer great dimensional stability in small, precision gears. It tolerates temperatures to 220 °C and has high chemical resistance and low mould shrinkage. It has been moulded to tooth thicknesses of about 0.066 mm. 

We will discuss the case where the motion of heavy atoms is confined to two dimensions, while the motion of light atoms can be either two- or three-dimensional. It will be shown that the Hamiltonian 10.76 with Ues in 10.44 supports the first-order quantum gas-crystal transition at T = 0 [68], This phase transition resembles the one for the flux lattice melting in superconductors, where the flux lines are mapped onto a system of bosons interacting via a two-dimensional Yukawa potential [73]. In this case Monte Carlo studies [74,75] identified the first-order liquid-crystal transition at zero and finite temperatures. Aside from the difference in the interaction potentials, a distinguished feature of our system is related to its stability. The molecules can undergo collisional relaxation into deeply bound states, or form weakly bound trimers. Another subtle question is how dilute the system should be to enable the use of the binary approximation for the molecule-molecule interaction, leading to Equations 10.76 and 10.44. 

Note that the threshold field here is smaller than the threshold field of the Freedericksz transition in the regular liquid crystal cell consisting of two parallel substrates with the same cell gap, for the following reason. In the regular cell the hquid crystal is anchored by the two-dimensional surface of the substrate, while in the polymer-stabilized hquid crystal cell here, the liquid crystal is anchored by the one-dimensional polymer fiber. 

All-Aurum and Aurum -metal hybrid hard disk carriers provide exceptional dimensional stability at elevated temperatures (see Fig. 10.3). Aurum injection-molded liquid crystal display (LCD) glass carriers can withstand LCD processing temperatures. 

A theoretical investigation of the stability of nematic liquid crystals with homeotropic orientation requires a three-dimensional approach. Helfrich s one-dimensional theory predicts the dependence of the threshold of the instability on the magnitude of Ae, as shown by curve 2 in Fig. 5.8, according to which the electrohydrodynamic instability should be observed when either Ae < 0 (and consequently the bend Frederiks effect reorientation will not take place), or when small Ae > 0. In Helfirich s model the destabilizing torque as dvzjdx is responsible for this instability, which replaces the destabilizing torque a dvzjdx in the equation for the director rotations (5.27). Although the torque is small ( a3 -C o 2 ) it is not compensated for (e.g., when Ae = 0) by anything else apart from the elastic torque. 

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