Structural characterization of Chloride Salt of conducting polyaniline obtained by XRD, SAXD, SAXS and SEM

Emeraldine-salt polyaniline form (ES-PANI) was chemically synthesized using hydrochloric acid at time synthesis ranging from 0.5 to 48 h and characterized by X-ray diffraction (XRD), LeBail fit, Small-angle X-ray diffraction (SAXD), Small-angle X-ray Scattering (SAXS) and Scanning Electron Microscopy (SEM). Crystallinity and crystal data (a = 5.7122, b = 17.8393, c = 22.8027, α = 83.1575, β = 84.6971 and γ = 88.4419) were obtained by XRD and showed that the crystallinity did not vary with the time synthesis. LeBail fit revealed that the crystallites were very small lamellae with global average size around 39 Å. By SAXS it was obtained the particle Radius of Giration (Rg) of 320 Å. The maximum particle size (Dmax) of 650 Å was obtained from the pair-distance distribution function (p(r)). SEM images showed a fiber morphology formed by interconnected non homogeneous nanospheres. Electrical conductivity of the samples was in ∼1.84 × 10−4 S/cm.

► The structural study of polymers is always an important topic for research, since their properties are related to its structure. It was showed that the time synthesis does not improve the crystallinity of the polymer and the slow addition of the reagents promotes a better crystallinity.
► The use of SAXD/XRD to obtain the full diffractogram for PANI is a new topic in the literature. The novelty of this study is a peak located at 2θ = 6.2° and another one at 3.7°.
► The use of SAXS, XRD and SEM techniques to characterize polymers provide a comprehensive and systematic study on the structural and morphological characterization of these materials.
► The use of LeBail fit applied in polymers is a new important topic in structural researches of these materials. In this study an unit cell of Chloride Salt of polyaniline was proposed by changing a b-axis to accommodate the Cl− ions and a speculative structural model was proposed.