Structural and morphological characterization of Poly(o-ethoxyaniline) Emeraldine-salt form using FTIR, XRD, LeBail Method and SEM

Head-to-Tail and Head-to-Head Molecular Chains of Poly(p-Anisidine): Combined Experimental and Theoretical Evaluation

Poly(p-anisidine) (PPA) is a polyaniline derivative presenting a methoxy (–OCH₃) group at the para position of the phenyl ring. Considering the important role of conjugated polymers in novel technological applications, a systematic, combined experimental and theoretical investigation was performed to obtain more insight into the crystallization process of PPA. Conventional oxidative polymerization of p-anisidine monomer was based on a central composite rotational design (CCRD). The effects of the concentration of the monomer, ammonium persulfate (APS), and HCl on the percentage of crystallinity were considered. Several experimental techniques such as X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), multifractal analysis, Nuclear Magnetic Resonance (¹³C NMR), Fourier-transform Infrared spectroscopy (FTIR), and complex impedance spectroscopy analysis, in addition to Density Functional Theory (DFT), were employed to perform a systematic investigation of PPA. The experimental treatments resulted in different crystal structures with a percentage of crystallinity ranging from (29.2 ± 0.6)% (PPA1_HT) to (55.1 ± 0.2)% (PPA16_HT-HH). A broad halo in the PPA16_HT-HH pattern from 2θ = 10.0–30.0° suggested a reduced crystallinity. Needle and globular-particle morphologies were observed in both samples; the needle morphology might have been related to the crystalline contribution. A multifractal analysis showed that the PPA surface became more complex when the crystallinity was reduced. The proposed molecular structures of PPA were supported by the high-resolution ¹³C NMR results, allowing us to access the percentage of head-to-tail (HT) and head-to-head (HH) molecular structures. When comparing the calculated and experimental FTIR spectra, the most pronounced changes were observed in ν(C–H), ν(N–H), ν(C–O), and ν(C–N–C) due to the influence of counterions on the polymer backbone as well as the different mechanisms of polymerization. Finally, a significant difference in the electrical conductivity was observed in the range of 1.00 × 10⁻⁹ S.cm⁻¹ and 3.90 × 10⁻¹⁴ S.cm⁻¹, respectively, for PPA1_HT and PPA16_HT-HH.

Poly(o-methoxyaniline) Chain Degradation Based on a Heat Treatment (HT) Process: Combined Experimental and Theoretical Evaluation

Poly(o-methoxyaniline) emeraldine-salt form (ES-POMA) was chemically synthesized using hydrochloric acid and subjected to a heat treatment (HT) process for 1 h at 100 °C (TT₁₀₀) and 200 °C (TT₂₀₀). The HT process promoted a progressive decrease in crystallinity. The Le Bail method revealed a decomposition from tetrameric to trimeric-folded chains after the HT process. The unheated POMA-ES presented a globular vesicular morphology with varied micrometric sizes. The heat treatment promoted a reduction in these globular structures, increasing the non-crystalline phase. The boundary length (S) and connectivity/Euler feature (χ) parameters were calculated from the SEM images, revealing that ES-POMA presented a wide distribution of heights. The TT₁₀₀ and TT₂₀₀ presented a narrow boundary distribution, suggesting smoother surfaces with smaller height variations. The UV-VIS analysis revealed that the transition at 343 nm (nonlocal π → π*) was more intense in the TT₂₀₀ due to the electronic delocalization, which resulted from the reduced polymer chain caused by the HT process. In addition to the loss of conjugation, counter ion withdrawal reduced the ion-chain interaction, decreasing the local electron density. This result shows the influence of the chlorine counter ions on the peaks position related to the HOMO → LUMO transition, since the π → polaron transition occurs due to the creation of the energy states due to the presence of counter ions. Finally, the electrical conductivity decreased after the HT process from 1.4 × 10⁻⁴ S.cm⁻¹ to 2.4 × 10⁻⁶ S.cm⁻¹ as result of the polymer deprotonation/degradation. Thus, this paper proposed a systematic evaluation of the POMA molecular structure and crystallite size and shape after heat treatment.

Facile fabrication and application of poly(ortho-phenetidine) nanocomposite coating for solid-phase microextraction of carcinogenic polycyclic aromatic hydrocarbons from wastewaters

The waters and wastewaters around industrial areas are heavily polluted and have adverse effects on the ecosystems. The present study is mainly focused on the electropolymerization of ortho-phenetidine and co-deposited on a steel wire along with graphene oxide nanosheets as a novel coating for solid-phase microextraction of polycyclic aromatic hydrocarbons (PAHs) from aqueous media prior to gas chromatography-mass spectrometry. PAHs are composed of multiple aromatic rings which have been linked to skin, lung, bladder and liver. Cancer is a primary human health risk of exposure to PAHs. To obtain a firm and stable coating, several empirical factors relevant to the electrochemical process were investigated. Characterization for chemical structure and surface morphology of the synthesized nanocomposite was conducted with FT-IR spectroscopy and FE-SEM, respectively. XRD and TGA were applied to study the other properties of the nanocomposite. Some essential items involved in microextraction process were also checked in details. Under optimized case, validation parameters were assessed. Wide linearity (0.005-5.0 ng mL^-1), low detection limits (0.4-4.3 pg mL^-1) and good repeatability (3.6-9.5%) and reproducibility (7.6-11.8%) were achieved. The developed method was utilized to analyze contaminated real samples such as wastewater samples from coal processing industries and agricultural water samples collected from the vicinity of the industry in different seasons and high recoveries were obtained, finally.

Effect of graphene oxide on the bioactivities of nitrifying and denitrifying bacteria in aerobic granular sludge

With the widespread application of graphene oxide (GO), it would be inevitably released into wastewater treatment plants (WWTPs) and get involved in the biochemical process. So far, there are controversies on the effects of low GO concentration (0.05-0.1 g/L) on the nitrogen removal process. Therefore, this study essentially investigates any potential effects of GO on wastewater microbial communities functions. In present study, the nitrifying and denitrifying batch tests were introduced to investigate the influence of 0.06 g/L of GO on bacteria. The results showed that GO could be easily combined with the aerobic granular sludge (AGS), and NH₄⁺-N was sharply absorbed, which directly promoted the bioactivities of ammonium oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) and extracellular polymeric substances (EPS) production. The influence of GO on the denitrifying bacteria was negligible, which resulted in the stable EPS production. Furthermore, as inferred from the near maximum chemical reaction rates, there were no obvious changes on the microbial community functions during nitrogen removal process.