Polymeric liquid crystal

A special class of polymeric liquid crystals is obtained by attaching rigid side chains to a flexible backbone. Inasmuch as it is the side chains that engage in formation of the liquid crystalline domains, these systems are more closely akin to low molecular liquid crystals. Polymeric liquid crystals of this type are discussed by Rehage and Finkelmann in Vol. 60 of this series. 

Yoon DY, Flory PJ (1989) Res Soc Symp Proc 134 11 Luckhurst GR (1985) In Chapoy LL (ed) Recent advances in liquid crystal polymerization. Elsevier, London, p 105... 

K. Akagi, S. Katayama, H. Shirakawa, K. Araya, A. Mukoh, T. Narahara, Highly conductive polyacetylene film prepared by the liquid crystal polymerization method under magnetic field, Synth. Met., 17, 241-246 (1987). 

The first work on acetylene polymerization in a liquid crystal medium was done in the mid-1980s [50-56]. The liquid crystal polymerization method was used for the preparation of highly aligned PA films directly through the anisotropic reaction field produced by macroscopically oriented nematic liquid crystals used as a polymerization solvent for the Ziegler-Natta catalyst. 

The liquid crystal polymerization method was modified to prepare a vertically aligned poly acetylene film [58]. As a result, a film with a very curious morphology was formed that was composed of two layers. The layer on the solvent side had a vertically oriented fibrillar structure, whereas the layer on the acetylene gas side had a randomly oriented one. The modified method is very promising for visualizing the polymer growth process and clearly demonstrates that PA chains grow in a liquid crystal solvent. 

A method has been developed recently to eliminate the thermal process for producing polyacetylene films. This technique is a liquid-crystal polymerization... 

It should be mentioned that, for certain classes of liquid crystals (polymeric liquid crystals, smectic liquid crystals), the light scattering method allows the determination of the viscosity coefficients, whereas their measurement by means of mechanical methods is very difficult. 

A method has been developed recently to eliminate the thermal process for producing polyacetylene films. This technique is a liquid-crystal polymerization method, which allows oriented films to be prepared directly through an anisotropic reaction field (68-70). The field is produced by macroscopically orientated nematic liquid crystals, which are used as the polymerization solvent for a Ziegler-Natta catalyst. This technique yields highly oriented films in the trans configuration. This process produces polyacetylene with good conductivity (10 s/cm) without the need for thermal treatment and stretching, which causes defects and breaks fibrils in films. 

Penner T L, Schiidkraut J S, Ringsdorf H and Schuster A 1991 Oriented films from polymeric amphiphiles with mesogenic groups—Langmuir-Blodgett liquid-crystals/Macromo/ecu/es 24 1041-9... 

Inhibitors are usually added to butadiene and acrolein to prevent polymerization, but the system is not foolproof. Several runaways have occurred in tank trucks or tank cars containing acrolein. As it cooled, some of the liquid crystallized, leaving the inhibitor in solution. In other cases impurities have been left behind in the bulk liquid, and their concentration has risen sufficiently to start a runaway. 

Khoklov, A. R. and Grosberg, A. Yu. Statistical Theory of Polymeric Lyotropic Liquid Crystals. Vol. 41, pp. 53-97. 

Fig. 27 a and b. Schematic representation of the molecular structure of a side chain polymeric liquid crystals b polymer model membranes studied by 2H NMR... 

Polymeric Liquid Crystals in Materials Science and Technology Series , edited by A. Cifferi, W. R. Krigbaum, R, B, Meyer, Academic Press, N. Y. 1982... 

Monomers of die type Aa B. are used in step-growth polymerization to produce a variety of polymer architectures, including stars, dendrimers, and hyperbranched polymers.26 28 The unique architecture imparts properties distinctly different from linear polymers of similar compositions. These materials are finding applications in areas such as resin modification, micelles and encapsulation, liquid crystals, pharmaceuticals, catalysis, electroluminescent devices, and analytical chemistry. 

Linear polyurethanes, 26 Linear step-growth polymerizations, 13 Lipase-catalyzed polyesterifications, 83 Lipases, 82, 84 catalytic site of, 84 Liquefied MDIs, 211, 226-227 Liquid carbon dioxide, 206 Liquid-castable systems, 201 Liquid crystal devices (LCDs), alignment coating for, 269-270 Liquid crystalline aromatic polyesters, 35 Liquid crystalline polyesters, 25, 26, 48-53... 

Electro-optic materials can be made using liquid crystal polymer combinations. In these applications, termed polymer-stabilized liquid crystals [83,86], the hquid crystal is not removed after polymerization of the monomer and the resulting polymer network stabilizes the liquid crystal orientation. 

Serrette, A.G. and Swager, TM. (1994) Polar Superstructures Stabilized by Polymeric Oxometal Units Columnar Liquid Crystals Based on Tapered Dioxomolybdenum Complexes. Angewandte Chemie (International Edition in English), 33, 2342-2345. 

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