Polyacetylene magnetic polymers

The same authors 369,3701 also obtained similar results if the liquid crystal solvent was aligned by flow during the polymerization. They showed that the polymerization conditions lead to alignment of the fibrils within the polymer mass and of the chains within the fibrils polymers produced in this way could also be doped to a conductivity of 104 S cm-1 371). The morphology of polyacetylene produced by polymerization in a liquid crystal solvent, aligned both magnetically and by flow, has been studied by Montaner et al. 371). They show that the polymer film is made up of very long fibrils built from microfibrils. In one fibril, the orientation of microcrystalline domains with respect to the fibril axis is very well defined, whilst the orientation of the different fibrils in the sample spreads over 20°. 

Table VI includes the electrical and magnetic properties of the polymers studied. Polyacetylene is a semiconductor. In contrast, the conductivities of the Si-containing polyacetylenes are only in the order of S/cm,...

The unique properties of polymers such as polyacetylene, whose backbones consist of an alternating succession of single and double bonds, and most of which show extraordinary electrical, optical and magnetic properties including electrical conductivity when "doped" with electron donors or acceptors [35], are also outside the scope of this work. Sophisticated quantum mechanical treatments are required to predict these properties of such polymers. 

Polyacetylene has a simple chemical structure, and the addition of small amounts of various dopants (both acceptors and donors) dramatically changes its electrical, optical, and magnetic behavior. The acetylene was first polymerized to a linear zr-conjugated polymer by Natta et al. using a Ti(0—Pr)4/Et3Al in 1958. ... 

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. 

Several experiments have been carried out to confirm the physical properties of solitons in mns-polyacetylene [27]. Lately, this excitation has also been studied in another degenerate ground state conjugate polymer, poly(l,6-heptadiene) [28]. The onedimensional spin diffusion and associated spin dynamics are verified from electron magnetic resonance spectroscopy, nuclear magnetic resonance (NMR) spectroscopy and electron nuclear double resonance (ENDOR) measurements [13]. The density of neutral solitons has been estimated by Motsovoy and co-workers [29]. For more details on the physical properties of solitons, the reader is referred to a review article by Heeger and co-workers [13]. However, more theoretical and experimental work is... 

It has been generally accepted that polyacetylene has a planar structure, irrespective of cis and trans forms, due to ir-conjugation between the sp hybridized carbon atoms in the polymer chain [1,4]. If it were possible to modify such a planar structure of pofyacetylene into a hehcal one [13], one might expect novel magnetic and optical properties [14]. Here, we report polymerization of acetylene in asymmetric reaction field constructed with chiral nematic LCs, and show that pofyacetylene films formed by helical chains and fibrils can be synthesized [15]. Polymerization mechanism giving hehcal structure from primary to higher order and hierarchical spiral morphology is discussed. 

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