Multimorphologies of hydrochloride polyaniline synthesized by conventional and interfacial polymerization

The aim of this paper is to analyze the structure and morphology of the hydrochloride Polyaniline Emeraldine-salt form (PANI-ES) synthesized by conventional (PANI-ES/C-1 and PANI-ES/C-2) and interfacial (PANI-ES/I-1 and PANI/ES/I-2) polymerization using HCl 1 M and 2 M. The X-ray diffraction patterns (XRD) of PANI-ES/I-1 and PANI-ES/I-2 have presented higher crystallinity. Furthermore, the peak located at 2 theta = 18.3 degrees has not been reported in scientific literature. PANI-ES/C-1 and PANI-ES/C-2 presented closed crystallinity percentage around 50 (+/- 2) %, while PANI-ES/I-1 and PANI-ES/I-2 presented, respectively, 55 (+/- 2) % and 63 (+/- 2) % of crystallinity. However, PANI-ES/C-2, PANI-ES/I-1 and PANI-ES/I-2 have presented larger "b" unit cell parameter, from 8.9021 (A) over circle (PANI-ES/C-1) to similar to 16.2931 (A) over circle, due to the more efficient doping of the chloride ions. Fourier-transform Infrared Spectroscopy technique (FTIR) was useful to evaluate significant changes in the quinoid (Q) and benzenoid (B) bands: PANI-ES/C-1 and PANI-ES/C-2 presented the ratio Q/B, respectively, 0.4 and 0.6, indicating that the doping level by exposure to a higher dopant concentration has increased. An even more intense dopant action was verified in PANI-ES/I-1 and PANI-ES/I-2, presenting Q/B ratios of 0.7 and 0.9, respectively. These results reveal the more efficient doping level provided by the interfacial polymerization. Scanning Electron Microscopy (SEM) images showed that PANI-ES/C-1 presented short nanofibers, while PANI-ES/C-2 showed nanofibers length and diameter, respectively, around 61% and 13% higher than those found in PANI-ES/C-1. However, PANI-ES/I-1 and PANI-ES/I-2 presented four different types of morphologies (nanoplates, nanorods, nanofibers and nanoflowers) due to the peculiarity of this polymerization method. The difference of length and diameter between PANI-ES/C-1 and PANI-ES/I-2 nanofibers reaches 64% and 52%, respectively. Thermogravimetric Analysis (TGA) showed that the event related to the dopant release occurred for PANI-ES/I-1 and PANI-ES/I-2 in higher temperatures and larger temperature range, suggesting larger amount of dopant and better doping level. In addition, PANI-ES/C-1 was the lesser stable sample, while the more stable sample was PANI-ES/I-2. The PANI-ES/C-1 presented the lowest electrical conductivity, 0.48 x 10(-4) S cm(-1). Thus, PANI-ES/C-2, PANI-ES/I-1 and PANI-ES/I-2 have presented, respectively, electrical conductivity values around 0.75 x 10(-4) S cm(-1), 0.90 x 10(-4) S cm(-1) and 1.20 x 10(-4) S cm(-1). Furthermore, the interfacial polymerization methodology may favored higher electrical conductivity due to the better charge transport along the different morphologies. (C) 2017 Elsevier B.V. All rights reserved.