Nitrogen-containing polymers, structure

Phosphorus and nitrogen containing polymers were synthesized according to literature data (14-16). The chemical structure and some physical and chemical properties of these polymers together with the modifications occurring in cold plasma are presented in Table I. 

Scheme 1 Chemical structures of the different nitrogen-containing polymers, with X=CO, S02> O, HC=CH, and R=aliphatic groups...

From the point of view of structural analysis of nitrogen containing polymers, simultaneous application of both 13C and 15N NMR techniques will result in a more complete qualitative and quantitative definition of the polymer system, because the two nuclei/spectroscopies behave complementarily. 

V. C. Barry and P. W. D. Mitchell, Properties of periodate-oxidised polysaccharides. II. The structure of some nitrogen-containing polymers, J. Chem. Soc., (1953) 3631-3635. 

Bredas, J. L., Themans, B., and Andre, J. M., Valence effective Hamiltonian technique for nitrogen-containing polymers electronic structure of polypyrrole, pyrolized polyacrylonitrile and derivates, Phys. Rev. B, 27, 7827-7842 (1983). 

Depending on the structural characteristics in the polymer chain, different nitrogen containing polymers can be distinguished (see Fig. 2.2.3). 

Fig. 2.2.3 Characteristical structural units in nitrogen containing polymers (backbone).

Zn(DBS)2 also yields self-organized complexes with selected other nitrogen-containing polymers. For example, complexing polyamide 6 stoichiometrically with Zn(DBS)2 yields self-organized lamellar structure with a long period of 28 A [112] as well as it forms complexes with polyaniline [113], as will be discussed later. 

In other words, a synthetic route to polypeptides which requires only HCN and water is presented preformed a-amino acids are not necessary. According to Matthews, the pyrolysis of cyanide polymers can give nitrogen-containing heterocycles with purine and pyrimidine structures in other words, the HCN world ... 

Poly (acetylenes) [16], There are several catalysts available for polymerization of substituted acetylenes. Whereas Ziegler-Natta catalysts are quite effective for polymerization of acetylene itself and simple alkylacetylenes, they are not active towards other substituted acetylenes, e.g. phenylacetylenes. Olefin-metathesis catalysts (Masuda, 1985 Masuda and Higashimura, 1984, 1986) and Rh(i) catalysts (Furlani et al., 1986 Tabata, 1987) are often employed. In our experience, however, many persistent radicals and typical nitrogen-containing functional groups serve as good poisons for these catalysts. Therefore, radical centres have to be introduced after construction of the polymer skeletons. Fortunately, the polymers obtained with these catalysts are often soluble in one or other organic solvent. For example, methyl p-ethynylbenzoate can be polymerized to a brick-coloured amorph- See the Appendix on p. 245 of suffixes to structural formula numbers. 

Lahaye J, Nanse G, Bagreev A, Strelko V (1999) Porous structure and surface chemistry of nitrogen containing carbons from polymers. Carbon 37(4) 585-590... 

Perhaps one of the best known syntheses of a heterocyclic polymer via the modification method is the generation of nitrogen-containing ladder polymers by pyrolysis of polyacrylonitrile) (77MI11109). The thermolysis is known to take place in discrete steps. The first step in the sequence, which can take place with explosive violence if the heating rate is not sufficiently slow, occurs at about 150 °C and can be detected by the onset of intense color formation. The product of this reaction (Scheme 101) is the cyclic tetrahydropyridine ladder structure (209). The next step, which is conducted in the presence of air at ca. 250 °C, involves the thermooxidation of polymer (209) to form what is best described as terpolymer (210) containing dihydropyridine, pyridone and pyridine units. 

The structure determination of Zn(en)(NCS)Cl reveals monomeric tetrahedral zinc coordinated to thiocyanate via nitrogen.179 A structure determination of Cd(en)(N02)2 reveals a polymer containing cadmium in a seven-coordinate pentagonal prismatic environment the en functions as a bridging ligand, as does one of the nitrites.180... 

A large number of polymer materials are based on nitrogen containing monomers, such as urea and related compounds, various amides, amines etc. The most frequent nitrogen forms found in polymers are primary, secondary and tertiary amides, respectively, the later usually being a part of the network structure. Since the... 

The basic monomers of nucleic acids are nucleotides which are made up of heterocyclic nitrogen-containing compounds, purines and pyrimidines, linked to pentose sugars. There are two types of nucleic acids and these can be distinguished on the basis of the sugar moiety of the molecule, Ribonucleic acids (RNA) contain ribose, while deoxyribonucleic acid (DNA) contains deoxyribose. The bases cytosine (C) adenine (A) and guanine (G) are common in both RNA and DNA. However, RNA molecules contain a unique base, uracil (U), while the unique DNA base is thymidine (T). These differences in the base structure markedly affect the secondary structures of these polymers. The structures of DNA and RNA are outlined in Appendix 5.2. 

For example, there is considerable interest in the preparation of sulfur-nitrogen polymers that have organic substituents on the sulfur atoms.56 This could help alleviate the intractability problem mentioned, and could also give rise to a series of polymers that parallel the phosphazenes in their structural variability. A series of polymers with S-N backbones of this type has been prepared, but with oxygen atoms as some of the substituents. The basic structure has the repeat unit -RS(=0)(N)- or -FS(=0)(N)-but they have not yet been studied in detail. The fluorine-containing polymer, however, is known to be a tough elastomer which is unaffected by water, acids, or bases up to 100 °C.7... 

There are many examples of compounds, usually short polymers, that spontaneously form double helical structures. A classic example involves a number of bipyridyl ligands joined by short, flexible spacers. In the presence of Cu(I), which has both an affinity for nitrogen-containing ligands and a preference for a tetrahedral disposition of donor atoms, discrete double helical complexes are formed [23], A similar phenomenon gives rise to a triple helical motif when a metal that preferentially adopts an octahedral coordination geometry is used [24],... 

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