Polyaniline oligomers

In a complementary study of the interaction between polyanilinc and ITO, oligomeric polyaniline model compounds, namely phenyl-capped amino (PC2) and imino (PC20X) dimers [113, 114] have been used. The chemical structures of the polyaniline oligomers are displayed in Figure 5-20. Both substances are soluble in... 

The vibrational spectra of different polyaniline oligomers, including B3, have been studied earlier by means of Raman and infrared spectroscopy, and... 

Dolan, A.R. and Wood, T.D. (2004) Analysis of polyaniline oligomers by laser desorption ionization and solventless MALDL/. Am. Soc. Mass Spectrom., 15, 893-899. 

Many other air-stable conducting polymers followed (Fig. 12.10) polypyrrole, polythiophene, polyaniline (which had been known since the nineteenth century as "aniline black"), and so on (Table 12.4). These polymers are semiconducting, not metallic, when "doped" with electron donors or acceptors the individual conjugated chains have finite length, so the conductivity is limited by chain-to-chain hopping. Also, if the individual strands exceed four or so oligomers, the conjugation tends to decrease, as the strand tends to adopt a screw-type distortion. The transport within each strand is attributed to polarons and bipolarons. 

The formation of -aminodiphenylamine is supposed to be the key intermediate in the formation of a dark green precipitate at the electrode surface during continued electrolysis of acidic aniline solutions. This has been characterized as an oligomer of aniline, for example, as the octamer emeraldine formed by a cascade of head-to-tail condensations [38,39]. Nelson, however, explained it as a mixture of mainly quinhydrone with a small amount of benzidine salt [37]. Today the electropolymerization of aniline under strongly acidic conditions is intensively studied as an important way to form the conducting polymer polyaniline [40] (see Chapters 31 and 32). 

Polythiophene randomly grafted with alkyl and aniline tetramer groups (157) was synthesized. The tetramer was chosen because it is the minimum oligomer size that mimics the electrochemical behavior of polyaniline, which shows semiconduction and conduction behavior depending on its state of oxidation and the pH. Transition from one structure to the other is illustrated in equation 23, where the electron mobility of quinonoid states (158) rearranging to isolated free radicals (159) is precluded after reduction to 160. A correlation was found between the electrochemical behavior and the UVV-NIR spectra of the 157 polymers255. 

W. Li and H.-L. Wang, Oligomer-assisted synthesis of chiral polyaniline nanofihers, J. Am. 

From the date recorded on oligomers, we have also studied in details the protonated emeraldine form of the polyaniline and have clarified the delocalization of the charged defects along the chain as a function of the solution acidity. 

Brown, C. E., Kovacic, P, Welch, K. J., Cody, R. B., Hein, R. E., and Kinsinger, J. A., "Laser Desorption/Fourier Transform Mass Spectra of Polyfphenylene sulfide), Polyaniline, Poly(vinyl phenol). Polypyrene, and Related Oligomers Evidence for Carbon Clusters and Eeasibility of Physical Dimension Measurement," /. Polym. Sci. PolyttL Chem. Ed., 26,131-148,1988. 

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