The electronic absorption profiles of a polyaniline base (using NMP as a solvent) and of a polyaniline salt (dissolved in sulfuric and methanesulfonic acid) have been studied from 0.5 to 5.5 eV and compared with those of some constitutive bricks of the polyaniline repeated units: diphenylamine (BB), N,N′-diphenyl-1,4-phenylene-diamine (BBB) and -diimine (BQB) and the oxidized tetramer (BQBBa, a stands for a terminal amine group). Standard (∼100 nm) and short (10–20 nm) polyaniline chain lengths are considered. Resonant Raman profiles were determined for exciting energies ranging from 1 to 3 eV. In the cationic chains, the electronic absorbance per cycle is increased with the chain length but the formation of NH2+ groups in strong acids destroys the conjugation, leading to isolated phenyl rings. On the other hand, for polymer base chains, constant behavior is observed with length ≥16 nm and pernigraniline chain portions are evidenced from the analysis of the Resonant Raman profile. Although a semi-conduction amorphous-like behavior is deduced from Urbach's tail analysis for polyaniline base nanofilaments, a crystalline behavior is recognized for HCl intercalated films.

Polyaniline and their molecular models are used to analyze electronic modifications of chains caused by the metal surface vicinity. The adsorption of these molecules and their orientation oil platinum surfaces is here characterized by High Resolution Electron Energy Loss Spectroscopy (HREELS) using the selection rules for dipole mechanisms. Adsorbed layers of polyaniline tetramer also exhibit an electronic loss detected around 2.3 eV and here assigned to an intrachain exciton. Adhesion on metallic surfaces mainly involves an effective chemical bond to the surface, where the nitrogen doublet and the quinoïc group play a major role.

The short-range structure and disorder of polyanilines is discussed by considering backbone geometry, conformation and sp2/sp3 hybridization of nitrogen atom. The comparison between polymer and oligomer spectra shows that ring deformation modes are very sensitive to static/dynamic disorder. Low energy Raman and inelastic neutron allow to distinguish two class of emeraldine salts (ES-I/ES-II) already distinguished from X-Ray Powder patterns.

Raman and infrared reflection spectra in the backbone deformations and lattice modes range (10-1000 cm(-1)) of EB/ES-I and EB/ES-II polyanilines are discussed and compared with those of an oligomer (BQBBa) and of the constitutive bricks of the polyaniline skeleton: diphenylamine (BQB), N,N-'diphenyl-1,4-phenylenediamine (BBB), and N,N'-diphenyl-1,4-phenylenediimine (BQB). Short-range structure, scaling motif, and disorder are discussed. Emphasis is given to the relationship between hybridization, short-range structure, disorder, and optical properties. Ring, CH deformations, and librational/translational modes appear very sensitive to the static and dynamic disorder. Results show that vibrational spectroscopy allows to distinguish the two classes of polyaniline (ES-I and ES-II), whatever the inserted anion. The sketch of a continuous change of angle between the rigid virtual N-ring-N bond is proposed to describe the static orientational disorder.

A chemically prepared emeraldine chloride powder has been studied by high-resolution electron microscopy. Two kinds of grains with varying degrees of crystallinity were observed: (i) Rolled sheets (20-100 nm in diameter) (aggregates, disks, or ribbons ?) with an amorphous surface layer are identified as the EB-II polymer polymorph because of the centering of the cell and characteristic interreticular distances. A periodicity (similar to 5 nm) ascribed to the growth irregularity of the pristine polymeric aggregate is observed around the catalytic center. (ii) Crystalline grains (20-50 nm) exhibiting well-characterized 0.59-nm interreticular spacing are identified as the ES-I emeraldine salt. The interchain structural order appears stronger than the order along the polyaniline chain, according to the bond angle flexibility. The observed concentric nanostructure supports both the sketch of ordered islands and the paracrystal descriptions.

La comparaison des spectres IR et Raman de basses frequences permet de discuter les structures locales des differentes formes de polyanilines a la lumiere de composes modeles (diphenylamine, N,N'-diphenyl-1.4 -phenylenediamine, oligomere).

UV-vis-nIR optical absorption and Raman spectra of solutions of polyaniline in anhydrous and hydrated concentrated sulfuric acid as well as X-ray diffraction patterns of more or less dried polyaniline salts have been investigated Results show that water leads to the conducting form of polyaniline and promotes the crystallinity of powders. Local structures, types of disorder and sites available for protonic species are discussed.

The nature of polyaniline (2A or 2S form) dissolved in concentrated sulfuric and methanesulfonic acid has been investigated by (UV-Vis-NIR) optical absorption and Raman scattering using various exciting laser lines. Two different palaronic species have been evidenced and selectively analysed, using 15N labelled and perdeuterated ring derivatives. Addition of water induces formation of 2S-like materials, probably forming a sol and not a true solution. The achievement of the metallic state seems to be related to the ordering of the chains interacted with water, oxonium ions and anions.