TEM, XRD and AFM study of poly(o-ethoxyaniline) films: new evidence for the formation of conducting islands

Abstract

The existence of conducting islands in polyaniline films has long been proposed in the literature, which would be consistent with conducting mechanisms based on hopping. Obtaining direct evidence of conducting islands, however, is not straightforward. In this paper, conducting islands were visualized in poly(o-ethoxyaniline) (POEA) films prepared at low pH, using Transmission Electron Microscopy (TEM) and atomic force spectroscopy (AFS). The size of the islands varied between 67 and 470 Å for a pH = 3.0, with a larger average being obtained with AFS, probably due to the finite size effect of the atomic force microscopy tip. In AFS, the conducting islands were denoted by regions with repulsive forces due to the double-layer forces. On the basis of X-ray diffraction (XRD) patterns for POEA in the powder form, we infer that the conducting islands are crystalline, and therefore a POEA film is believed to consist of conducting islands dispersed in an insulating, amorphous matrix. From conductivity measurements we inferred the charge transport to be governed by a typical quasione dimensional variable range hopping (VRH) mechanism.

Nanodiamond-mediated crystallization in fibers of PANI nanocomposites produced by template-free polymerization: Conductive and thermal properties of the fibrillar networks

“…The motion of such carriers along a backbone and the hopping among neighboring backbones and among fibers or globules, contributes to the conduction through all the material [19]. The conduction model associated with this situation is usually depicted by considering the existence of conductive islands, which are crystalline regions of polymer where the chains are orderly arranged, and which are embedded in the not conductive amorphous polymer phase [19,20]. It follows that in this perspective is crucial to assess both the state of oxidation and the spatial organization of the polymer chains when the growth and the arrangement of the PANI chains is triggered by the presence of DND fillers.…”

Rigid and semi rigid polyurethane resins: A structural investigation using DMA, SAXS and Le Bail method

“…Nevertheless it has been used to characterize some polymeric materials [16][17][18][19][20]. In order to be able to estimate R factors related to integrated intensities, Rietveld [21] stated: ''a fair approximation to the observed integrated intensity can be made by separating the peaks according to the calculated values of the integrated intensities, i.e.…”

Oxidative Polymerization of Aniline: Molecular Synthesis of Polyaniline and the Formation of Supramolecular Structures

“…Inhomogeneous morphology of the polymer, as well as inhomogeneity in the properties of macroscopic samples, was revealed by X-ray structural analysis, luminescence, ellipsometry, electron and atomic force microscopy (Leite et al 2008;Lux et al 2003). Crystalline islands were observed as dense inclusions in amorphous matrix with the aid of high-resolution transmission electron microscopy and atomic force microscopy (Mazerolles et al 1999).…”