Small molecule and polymeric liquid

II. ELECTRIC AND MAGNETIC FIELD EFFECTS ON SMALL-MOLECULE AND POLYMERIC LIQUID CRYSTALS... 

In this brief review, we strive to construct a coherent picture of our current theoretical understanding of the flow and rheology of small-molecule and polymeric nematic liquid crystals. Owing to space limitations, we have presented results selectively, based more on the need to tell a somewhat coherent story than the significance of the work. 

The phase area 4 in Fig. 6.1 is less likely for liquid crystals than for condis crystals since the small increase in order that is needed to change a mobile melt into a mobile liquid crystal occurs fast and is usually completely reversible as seen in the reversible transition shown in TMDSC of Fig. 5.144 for a small molecule and the upper curves of Fig. 5.154 for a macromolecule. Once in phase area 2, the polymeric liquid crystals will, however, not crystallize completely on cooling, but rather become a semicrystalline material. In the present scheme, they will produce metastable phase areas 9, followed by 10. 

During the liquefaction process, the biomass is decomposed into small molecules, and then re-polymerized to form liquid fuels ... 

Permeation of gases, liquids, and vapors through a polymeric film can be looked at as a three-step process as follows (1) the rate of dissolution of the small molecules in the polymer, (2) the rate of diffusion of the small molecules in the polymer film in accordance with the concentration gradient, and (3) the energies of the smaller molecules on the opposite side of the polymer. 

Synthesis of polymeric capsules involves polymer self-assembly on many levels and length scales. Approaches to their synthesis include cases where monomers are polymerized around a liquid template, premade polymers are assembled around liquid and solid templates, premade particles are assembled around templates, and small molecules or polymers assemble spontaneously. Each method offers unique challenges and advantages, and each allows the production of capsules with different properties. 

Until now, i.e., in 25 years of research, only two reviews on liquid crystalline crown ethers have been published [8, 9]. As both reviews cover the field only partially and, e.g., the fascinating polymeric crown ethers as well as taper-shaped liquid crystalline crown ethers are not discussed, we decided to give the first comprehensive review. The present chapter will be structured according to the molecular structure of the mesogens. The discussion of each type of crown ether mesogen will start with small molecules, continue with polymeric compounds, and conclude with possible applications (where applicable). 

Despite their solid appearance, within the gel the liquid component is mobile and is only held by capillary forces. The solid network can be either a covalent polymer or a supramolecular assembly of small molecules. The latter class of compound, termed low molecular weight gelators (LMWG) of which 14.11 14.15 are examples, is perhaps of most interest to supramolecular chemists. Perhaps the most well known gels are metal oxide based polymeric materials produced by the sol-gel process. The sol-gel process involves the hydrolysis and polycondensation of monomeric metal salts such as early transition... 

---