Pure polymer liquid crystals

PHASE DIAGRAMS OF PURE POLYMER LIQUID CRYSTALS... 

Development and relaxation of orientation in pure polymer liquid crystals and blends... 

Definitions of basic terms relating to low-molar-mass and polymer liquid crystals (lUPAC Recommendations 200 ), Pure Appl. Chem. 73, 845-895 (2001). 

The last polymer mentioned in Table 10.9 is poly(p-phenylene terephthalamide). This polymer is spun from its solution in pure sulphuric acid (100%), a dope that exhibits mesomorphic (=liquid crystalline) behaviour it is optically anisotropic and is nematic in character. A number of other polymers, containing rigid elements in the chain have melts of polymer liquid crystals, with a high birefringence and a non-linear optical behaviour in electric fields. 

Molecular composites (MCs)—which are polymer liquid crystals and PLC blends. As in HCs, there is a rigid reinforcement. However, the reinforcement is at the molecular level—what applies to pure PLCs as well as to PLC-containing blends. Now, against the background just provided, and before going into details, let us compare PLCs with the most widely used type of polymers, that is EPs. Such comparisons have been made before [9,25,26,27] one can summarize them by saying that PLCs... 

The encapsulated cholesteric liquid crystals are suitable for flexible displays with plastic substrates. They have much higher viscosities than pure cholesteric liquid crystals and can be coated on substrates in roll-to-roll process [71,72]. The polymers used for the encapsulation have good adhesion to the substrates and can make the materials self-adhesive to sustain the cell thickness. Furthermore, the encapsulated Ch liquid crystals can no longer flow when squeezed, which solves the image-erasing problem in displays from pure cholesteric liquid crystals where squeezing causes the hquid crystal to flow and to be switched to the planar state. 

This book was conceived as a renewed version of the earlier published original book, Electro-Optical and Magneto-Optical Properties of Liquid Crystals (Wiley, Chichester, 1983) written by one of us (L.M. Blinov). That book was first published in Russian (Nauka, Moscow, 1978) and then was modified slightly for the English translation. Since then new information on electrooptical effects in liquid crystals has been published. Novel effects have been discovered in nematics and cholesterics (such as the supertwist effect), and new classes of liquid crystalline materials, such as ferroelectric liquid crystals, appear. Recently, polymer liquid crystals attracted much attention and new electrooptical effects, both in pure polymer mesophases and polymer dispersed liquid crystals, were studied. An important contribution was also made in the understanding of surface properties and related phenomena (surface anchoring and bistability, flexoelectricity, etc.). 

Basic Definitions of Terms Relating to Low-Molar-Mass and Polymer Liquid Crystals Pure Appl. Chem. 73 (2001) 845. 

M. Baron and R. F. T. Stepto, Pure Appl. Chem., 74,493 (2002). (Definitions of Basic Terms Relating to Polymer Liquid Crystals.)... 

Aciemo D, Naddeo C (1994) Blends of PEEK and PET-PHB 60 a preliminary study on thermal and morphological aspects. Polymer 35(9) 1994-1996 Baron M, Stepto RFT (2002) Definitions of basic terms relating to polymer liquid crystals, lUPAC commission on macromolecular nomenclature. lUPAC recommendations. Pure Appl Chem 74 (3) 493-509... 

Fig. 6.2 The variation of rotational viscosity (ye) with temperature difference (T — T ) for polymer-stabilized ferroelectric liquid crystal and pure ferroelectric liquid crystal. The units are taken arbitrarily...

Engel M, Hisgen B, Keller R, Kreuder W, Reck B, Ringsdorf H, Schmidt HW, Tschmner P (1985) Synthesis, structure and properties of liquid crystalline polymers. Pure Appl Chem 57 1009-1014 Finkelmann H (1982) Polymer Liquid Crystals. Academic ftess. New York Finkelmann H, Rehage G (1980) Investigations on liquid crystalline polysiloxanes, 1. Synthesis and characterization of linear polymers. Makromol Chem Rapid Commun 1 31-34 Finkelmann H, Rehage G (1984) Liquid crystal side chain polymers. Liquid crystal polymers II/III. Adv Polym Sci 60/61 99-172... 

Many polymers are capable of forming mesophases in either aqueous or non-aqueous solvents. Furthermore, liquid crystal phases may form for pure... 

On a side note, Ouskova and co-workers also reported that the composite of magnetic /i-FejOs nanorods in 5CB showed lower threshold voltages than pure 5CB, and that the sensitivity of the nematic liquid crystal to external magnetic fields was increased in the presence of such magnetic nanorods [451]. Finally, several groups interested in the macroscopic organization and orientation of nanorods also reported on the formation of a lyotropic liquid crystal phase induced by the self-assembly of polymer-coated semiconductor nanorods [453—457], which might be used to improve the device performance, for example, of solar cells. 

The rapid growth of the number of publications concerning polymeric liquid crystals indicates that we should expect the appearance of new fundamental studies on the transition of rigid- and semirigid-chain polymers into this state. The range of moderately concentrated solutions for these polymers is studied sufficiently well, while the development of the methods of establishing the liquid. crystalline state in superconcentrated systems and in pure polymers with semirigid chains, as well as the analysis of kinetics of phase transitions, are the subject for further theoretical and experimental works. 

Finally, the possibility of pure optical switching has been demonstrated in principle by photoinducing supramolecular helical arrangements of smectic domains in some liquid crystal azo polymer films." The photoinduced chirality is pronounced and stable (our oldest sample is still fairly young), but the process is again slow, because it requires reorientation of whole domains. 

N,N-Dimethylacetamide (DMAC). The two polymers exhibit similar conformations and both exist in anisotropic phases above a certain critical concentration. It was found that when the ternary systems were examined, two anisotropic phases exist above the critical volume fraction. Further, each of the stable anisotropic phases contain pure polymer. The authors conclude that miscibility between polymers forming the same type of mesophase isn t necessarily observed, in contrast to low molecular weight liquid crystals. 

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