Nematic liquid crystals polyacetylene

Montaner et al. [74] have used electron diftraction to characterize Araya polyacetylene [21], prepared at 10°C from a Shirakawa catalyst system dissolved in a nematic liquid crystal, oriented by a magnetic field. The mosaic (orientation distribution) is broad, approximately 20° with respect to the fibre axis. A later x-... 

On the other hand, orientation is one of the most important factors to enhance the conductivity of one dimensional pi-conjugated polymers like polyacetylene. Several attempts were made to obtain an oriented polyacetylene [3-5]. Akagi and Shirakawa applied magnetic force into a polymerization system consisting of nematic liquid crystals and obtained a highly oriented polyacetylene. Kahlert and Leising synthesized an oriented polyacetylene film by pyrolyzing prepolymers. Ozaki polymerized acetylene on the surface of benzene crystals and prepared an oriented polyacetylene. 

Lyotropic Di-substituted Polyacetylenes that Exhibit High Dissymmetry Factors in Circularly Polarized Luminescence Through the Chiral Nematic Liquid Crystal Phase... 

Helical Polyacetylene Synthesized in Chiral Nematic Liquid Crystal... 

Chiral Dopants and Chiral Nematic Liquid Crystals Acetylene Polymerization in Chiral Nematic Liquid Crystal Characterization of Helical Polyacetylene Film... 

Piao, G., et al. 2001. Synthesis of well-controlled helical polyacetylene films using chiral nematic liquid crystals. Curr Appl Phys 1 121. 

K. Akagi, S. Katayama, M. Ito, H. Shirakawa, K. Araya, Direct synthesis of ahgned cis-rich polyacetylene films using low-temperature nematic liquid crystals, Synth. Met., 28, 51-56 (1989). 

K. Akagi, Helical polyacetylene synthesized in chiral nematic liquid crystal, in Handbook of Conducting Polymers, 3rd edn. Conjugated Polymers, ed. T. A. Skotheim, J. R. Reynolds, CRC Press, New York, 2007, Chapter 3, pp. 3-14. 

Goh, Munju et al. From helical polyacetylene to helical graphite synthesis in the chiral nematic liquid crystal field and morphology-retaining carbonisation. Chemical Society Reviews. 2010, 39, 2466-2476. 

In this chapter, I outlined recent developments of a new polymerization techniques using a asymmetric liquid crystal reaction field of the N -LC phase, focusing on helical polyacetylene with a super-hierarchical spiral structure (H-PA). Chiral binaphthyl axially chiral derivatives are added as a chiral dopant to nematic liquid crystal to produce the chiral N -LC phase. 

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. 

Oriented polyacetylene films have been synthesized by using a nematic liquid crystal as a polymerization solvent. The maximum value of parallel electrical conductivity of the films doped with AsFs was 11,000 S cm [17]. The use of an aged mixture of Ti(OC4Hc,)4-A1(C2H0. in silicone oil that has been mixed with various quantities of n-butyllithium, as the catalyst for the polymerization of acetylene, yields polyacetylene that is highly regular, compact, and crystalline, in well-defined parallel planes. When it is stretched and doped, the polyacetylene film shows a dramatic increase in conductivity to a value greater than lO S cm [18]. 

Crown ether binaphthyl derivatives 128-131 (Scheme 71) were synthesized and investigated by Akagi [139], Compounds 128-131 were used to induce chiral nematic phases (N ) in liquid crystals. It was found that the helical twisting power increased with decreasing ring size. Helical polyacetylenes were synthesized in the N phases. It was found that the interdistance between the fibril bundles of the helical polyacetylene was equal to the half-helical pitch of the N liquid... 

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