Polyacetylene, substituted

Unlike polyacetylene, substituted polyacetylenes are amorphous, electrically insulator soluble polymers.413 They are highly stable and not sensitive to oxidation. Since the substituents exert a strong steric effect, the polyene backbone is not copla-nar, and as a result, only limited conjugation is possible. 

An interesting extension of cyclooctatetraene polymerisation is the polymerisation of trimethylsilyl-substituted cyclooctatetraene to give soluble polyacetylene substituted with one trimethylsilyl group every eight carbon atoms [162], Such materials have been used to construct solar cells [165],... 

An example of an enantiomerically pure polymer is also shown [11]. Aoki et al. showed that films of a polyacetylene substituted with a (-)-p-pinene derivative formed an effective membrane for chromatographic resolutions of racemic mixtures. ( )-2-Butanol was resolved to 29.8% eje. and unsaturated polymers for both liquid-phase and gas-phase separation applications (8, 9, 79]. It has been suggested that the rigidity and irregularity of the highly substituted polyacetylene chain, combined with the presence of aliphatic substituents which reduce interchain interactions, are important for the polymers transport properties [10]. 

Polyacetylene is considered to be the prototypical low band-gap polymer, but its potential uses in device applications have been hampered by its sensitivity to both oxygen and moisture in its pristine and doped states. Poly(thienylene vinylene) 2 has been extensively studied because it shares many of the useful attributes of polyacetylene but shows considerably improved environmental stability. The low band gap of PTV and its derivatives lends itself to potential applications in both its pristine and highly conductive doped state. Furthermore, the vinylene spacers between thiophene units allow substitution on the thiophene ring without disrupting the conjugation along the polymer backbone. 

A route to processible polyacetylene, devised initially using classical initiators (Scheme 1i) 576-578 has been developed using well-defined molybdenum initiators to prepare conjugated polymers.579-585 They have also been employed to prepare polyacetylene via the polymerization of cyclooctate-traene, COT,586 and by the isomerization of poly(benzvalene).587 588 Substituted, and hence soluble, polyacetylene derivatives may be synthesized by polymerizing monosubstituted COT substrates.589-591... 

R. Sun, Q. Zheng, X. Zhang, T. Masuda, and T. Kobayashi, Light-emitting substituted polyacetylenes, Jpn. J. Appl. Phys., 38 2017-2023, 1999 and references therein. 

C yields a polymer with 90% cis content polymerization at 100°C yields a polymer with >90% trans content. Polyacetylene, doped with an oxidant or a reductant, showed promise as a polymeric semiconductor [Chien, 1984], That promise was not realized because of the oxidative instability of polyacetylene and emergence of cheaper and more stable polymer systems (Sec. 2-14j). Various substituted acetylenes such as phenylacetylene have also been studied [Kanki et al., 2002 Misumi et al., 2000],... 

This chapter surveys the polymerization of substituted acetylenes focusing on the research during this decade. Monomers and polymers, polymerization catalysts, controlled polymerizations, and functional polyacetylenes are discussed. Readers are encouraged to access other reviews and monographs on the polymerization of substituted acetylenes, and a,cj-diynes. ... 

Substituted polyacetylenes has been most intensively examined as gas-permeable materials aiming at practical application. These studies are motivated by the extremely high gas permeability of poly(TMSP), ... 

Table 9 Oxygen permeability coefficients (P02) and P02/PN2 of gas permeable substituted polyacetylenes...

Helix is the most common higher-order structure of synthetic polymers such as peptides, polymethacrylates, polychloral, polyisocyanides, polyisocyanates, and polysilanes. Polyacetylenes bearing appropriate substituents also form a helix. Substituted helical polyacetylenes are promising candidates for enantioselective permeable materials, polarization-sensitive electro-optical materials, asymmetric electrodes, and hence their synthesis is currently under intensive research. This section overviews the synthesis and properties of helical polyacetylenes recently reported. 

Substituted polyacetylenes may be produced through the ring-opening metathesis polymerization of substituted cyclooctatetraenes.127... 

Although the polymerization of diene monomers is most familiar for 1,3-dienes, as in the production of rubbers, the polymerization of 1,6-dienes to yield polymers containing six-membered rings ( cyclopolymerization ) has been well established for many years43. Gibson et al.441 have used cyclopolymerization of 1,6-diynes to prepare polymers which are effectively substituted polyacetylenes, the archetype being the polymerization of 1,6-heptadiyne ... 

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