A new assessment of the crystalline structure of undoped and doped aniline oligomers and polymers

Summary form only given. We describe hem the crystalline structure of aniline oligomers and polymers, derived from the aniline dimer p-aminodiphenylamine and aniline. The preparation of the oligomers has been accomplished via a modification of the usual polymerization route to polyaniline. The resulting powders have been successfully fractionated, using diethylether, methanol, tetrahydrofurane and dimethylformamide. The individual fractions differ by their molecular weight and their oxidation state, as has been derived from preliminary U.V. visible and MR spectra and by their solubility behaviour in concentrated sulfuric acid. Differences have been observed also in the chemical reactivity of the different powders. Especially the lower molecular weight materials ( ether/methanol soluble ) are quite reactive and undergo different chemical reactions when treated prolonged during the fractionation schedule. For example, crosslinking and uptake of oxygen are to be expected. The crystalline state of the different fractions depends strongly on the details of the crystallization procedure and on the molecular weight of the materials. Less convienient conditions and higher molecular weights yield samples with less defined crystalline features. Most important is the observation that all the crystalline structures in the undoped powders can be well accounted for by the EB II arrangement, proposed by Pouget et al. On the other hand, the characteristic crystalline arrangement of the doped samples does not show the main features of the ES II crystal arrangement. The ES II structure, reported by Pouget et al., probably results from degradation processes during the preparation of their powders.