Poly quinoxalines

Diisocyanobenzene (130) undergoes living polymerization to form the poly(quinoxaline-2,3-diyl)s 131, and the optically active helical polyfquinoxa-line-2,3-diyl) 132 is prepared from 131[123]. 

A considerable number of non-cross-linked aromatic and heterocyclic polymers has been produced. These include polyaromatic ketones, aromatic and heterocyclic polyanhydrides, polythiazoles, polypyrazoles, polytriazoles, poly-quinoxalines, polyketoquinolines, polybenzimidazoles, polyhydantoins, and polyimides. Of these the last two have achieved some technical significance, and have already been considered in Chapters 21 and 18 respectively. The most important polyimides are obtained by reacting pyromellitic dianhydride with an aromatic diamine to give a product of general structure (Figure 29.17). 

The preparation of helically well-ordered polymers with stable screw-sense, which is able to be transmitted to newly formed polymer main-chains effectively, is highly desired for the development of new methodology for the synthesis of optically active helical polymers. An aromatizing polymerization of 1,2-diisocyanobenzenes is promoted by methylpalladium(II) complexes, producing poly(quinoxaline-2,3-diyl)s.146-148 The polymerization proceeds with successive insertion of the two isocyano groups of the diisocyanobenzene to the carbon palladium bond of... 

In 1996, Yamamoto et al. [683] reported the EL from related poly(quinoxaline)s 585 (Chart... 

A great deal of literature attention has been devoted to polymers in this section as thermally stable polymers (B-80MI11101). While some very elegant syntheses have been conducted, the resulting polymers have been, for the most part, quite intractable materials not conducive to extensive screening for a variety of applications. Thus, aside from their bulk thermal performance, little else besides the conditions of synthesis is known about most of the polymers shown. Three notable exceptions about which considerable characterization and product information are available are poly(imides), poly(benzimidazoles) and poly(quinoxalines), and a short discussion is included concerning properties and applications of these polymers. 

The reaction of Grignard reagents with 1,2-diisocyanobenzenes results in formation of quinox-aline oligomers up to the hexaoligomer. Reactions of 5,8-dibromo-2,3-diphenylquinoxaline with a zero-valent nickel complex afford poly(2,3-diphenylquinoxaline-5,8-diyl). Chemical and electrochemical dehalogenation polycondensations of 2,6-dibromoquinoxaline using nickel complexes afford poly(quinoxaline-2,6-diyl). ... 

A synthetic sequence to poly(quinoxaline)s with (dialkylamino)vinyl substituents as solubilizing side-groups was developed by Yu and Dalton by combining the two approaches discussed [18, 19]. The condensation of a bis-(dialkylamino)vinyl-2,5-dichloro-l,4-benzoquinone (8) with tetraaminobenzene... 

Vapour Deposition Polymerisation. This is a little studied approach but one that offers significant potential for the fabrication of very thin films and for elaborate multilayer structures. A commercial process has been developed by the Ulvac Corporation in Japan to coat magnetic relay switches with an insulating polyimide layer. A polyamic acid is sythesised by co-deposition of two reactive monomers and is then thermally imidised. The same approach can be used for the condensation polymerisation of poly(azomethine)s, ° poly(ox-adiazoles) and poly(quinoxalines) all of which have been used in LED structures. This approach to polymer synthesis is ripe for further development. 

In this review, monoisocyanide polymers are denoted as poly(isocya-nide)s rather than using the systematic name, poly(iminomethylene)s , because the former name is more familiar to non-experts in this area. For example, poly(N- terf-butyliminomethylene) is denoted as poly( ferf-butyl isocyanide). On the other hand, the systematic name poly(quinoxaline-2,3-diyl) is used for polymers of 1,2-diisocyanobenzene to differentiate the fact that the polymerization process is accompanied by the formation of quinoxaline rings. 

Poly(quinoxaline)s showing liquid crystallinity have been prepared by palladium-mediated polymerization of 1,2-diisocyanobenzenes 78-80 bearing a series of alkoxymethyl substituents at the 4 and 5 positions (Scheme 52) [94]. Poly(quinoxaline)s can be classified as rigid-rod liquid... 

The more stable helical poly(quinoxaline)s (+)-91 and (-)-91 were obtained after the polymerization of the 3,6-di(p-propylphenyl) derivative 90 using (+)-87 and ( )-87 as chiral initiators [96]. No decrease in optical activity or in intensity of the CD spectra was observed under conditions similar to those applied to 89. These results indicate that the bulkiness of the... 

The polymerizations of the diisocyanides 86 and 88 were attempted using four binaphthyl-based initiators 98a-d, which differed only in the substituents on the binaphthyl group (Scheme 58). All the polymerizations produced poly(quinoxaline)s 99 and 100 that showed CD spectra characteristic... 

Poly(quinoxaline-2,7-diylquinoxaline-7,2-diyl-p-terphenyl-4,4 -ylene)578 21.9 38 188 0.0 631... 

Other examples of semiladder-like polymers include the poly(benzoxazole)s, poly(phenylene-13,4-oxadiazole)s, poly(quinoxaline)s, and poly(s-triazine)s. The high-temperature performance of these and other structures discussed are shown in Table 15.8. 

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