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/C1 and PANI-ES/C2) and interfacial (PANI-ES/I1 and PANI/ES/I2) polymerization using HCl 1 M and 2 M. The X-ray diffraction patterns (XRD) of PANI-ES/I1 and PANI-ES/I2 have presented higher crystallinity. Furthermore, the peak located at 2θ = 18.3° has not been reported in scientific literature. PANI-ES/C1 and PANI-ES/C2 presented closed crystallinity percentage around 50 (±2) %, while PANI-ES/I1 and PANI-ES/I2 presented, respectively, 55 (±2) % and 63 (±2) % of crystallinity. However, PANI-ES/C2, PANI-ES/I1 and PANI-ES/I2 have presented larger “b” unit cell parameter, from 8.9021 Å (PANI-ES/C1) to ∼16.2931 Å, 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/C1 and PANI-ES/C2 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/I1 and PANI-ES/I2, 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/C1 presented short nanofibers, while PANI-ES/C2 showed nanofibers length and diameter, respectively, around 61% and 13% higher than those found in PANI-ES/C1. However, PANI-ES/I1 and PANI-ES/I2 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/C1 and PANI-ES/I2 nanofibers reaches 64% and 52%, respectively. Thermogravimetric Analysis (TGA) showed that the event related to the dopant release occurred for PANI-ES/I1 and PANI-ES/I2 in higher temperatures and larger temperature range, suggesting larger amount of dopant and better doping level. In addition, PANI-ES/C1 was the lesser stable sample, while the more stable sample was PANI-ES/I2. The PANI-ES/C1 presented the lowest electrical conductivity, 0.48 × 10−4 S cm−1. Thus, PANI-ES/C2, PANI-ES/I1 and PANI-ES/I2 have presented, respectively, electrical conductivity values around 0.75 × 10−4 S cm−1, 0.90 × 10−4 S cm−1 and 1.20 × 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.