Aromatic structures monomer unit

Conjugated conducting polymers consist of a backbone of resonance-stabilized aromatic molecules. Most frequently, the charged and typically planar oxidized form possesses a delocalized -electron band structure and is doped with counteranions (p-doping). The band gap (defined as the onset of the tt-tt transition) between the valence band and the conduction band is considered responsible for the intrinsic optical properties. Investigations of the mechanism have revealed that the charge transport is based on the formation of radical cations delocalized over several monomer units, called polarons [27]. 

Three dimeric indole alkaloids of a new type, peceyline, peceylanine, and pelankine, have been isolated from a Sri Lankan apocynaceous plant, Petchia ceylanica Wight.876 The structures of these bases were determined mainly by n.m.r. spectroscopy. In their H spectra, all three alkaloids exhibit four aromatic singlets, one olefinic hydrogen multiplet, two methoxycarbonyl singlets, two N-methyl singlets, and two C-methyl doublets. One half of the non-aromatic carbon resonances in the 13C spectra show that one monomer unit is common to all three alkaloids, and inspection reveals that this unit must be based on vincorine... 

The non-aromatic portion of the second monomer unit in peceyline and peceylanine is also identical (13C spectra), and is based on vincorine epoxide. Since peceyline contains no methoxy-groups other than those in the ester functions, and its H aromatic resonances are consistent with an unsymmetrical dibenzofuran system, a possible structure for peceyline is (186). 

The resonances for the chain-end phenyl rings occur at 7.25-7.45 ppm while the resonances for the aromatic protons of the monomer units occur in the region from 6.50-6.70 ppm. A large amount of fine structure can... 

Figure 2. Modification concepts for para-linked aromatic polymers including typical monomer structures (a) monomer units of different length, (b) kinked comonomers, (c) double kinked comonomers, (d) crankshaft comonomers, (e) flexible lateral substituents, (f) bulky and stiff lateral substituents, and (g) monomers with non-coplanar conformation.

Aliphatic polyamides are macromolecules whose structural units are characteristically interlinked by the amide linkage —NHCO—. The nature of the structural unit constitutes a basis for classification. Aliphatic polyamides with structural units derived predominantly from aliphatic monomers are members of the generic class of nylons, whereas aromatic polyamides in which at least 85% of the amide linkages are directly adjacent to aromatic structures have been designated aramids. This chapter is concerned with nylons, especially those of commercial importance. Aramids are discussed in a separate chapter. 

The Refs. [359, 360] report on different s5mtheses of isomeric aromatic polyketones. Three isomeric aromatic polyketones, containing units of 2-trifluoromethyl- and 2,2 -dimetoxybisphenylene were S5mthesized in Ref [326] by means of direct electrophylic aromatic acylated polycondensation of monomers. Two isomers of polyketone of structure head-to tail and head-to head contain the links of 2-trifrluoromethyl-4,4 -bisphenylene and 2,2 -dimethoxy-5,5 -bisphenylene. 

The structure of polythiophene is based on monomer units coupling through their 2,5-positions (a,a ), which preserves the aromaticity in the polymer [192,260]. This is consistent with infrared spectra, in which absorption bands found in the monomer are observed in the polymer. Dopant ions are probably responsible for the formation of new bands in the spectra of doped polythiophene, since the frequencies of the new bands shift with different types of dopants. Furthermore, elec-trochemically synthesized polythiophene exhibits distinctly different absorption bands from chemically prepared poly-2,4-thiophene [261]. 

The results obtained indicate to the intramolecular interaction of monomer units modified by aromatic amines with vinyl groups of polydiene macromolecules at syndiotactic 1,2-PB modification. This leads to the formation of macromolecules of the branched and linear structure (Scheme 12) ... 

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