Ceramic nanocomposites constituted by a matrix ofα-Al2O3microparticles reinforced by polyaniline emeraldine-salt form (PANI-ES) nanoparticles were prepared byin situpolymerization and characterized structural and morphologically. Peaks related to both materials were observed through XRD technique: PANI-ES presented peaks at2θ= 8.9, 14.9, 20.8, 25.3, 27.1, and 30.0° and inα-Al2O3phase peaks were found at2θ= 25.6, 35.2, 37.9, 43.5, 52.6, 57.6, and 68.1°. Nanocomposite crystallinity percentage was estimated around 70%. SEM showed a polymerization of PANI-ES over alumina plates. By Le Bail method it was observed that PANI-ES andα-Al2O3have crystallite average size around, respectively, 41 and 250 Å. By FTIR analysis characteristic absorption bands of both materials were identified. Additional bands indicating new chemical bonds were not observed, suggesting that nanocomposite was formed by physical deposition. Nanocomposite DC electrical conductivity was found around 0.24 S/cm (against1.84×10-4 S/cm for pure PANI-ES), showing an increase of about 1,300 times compared to the pure PANI-ES at room temperature. Thus, this paper showed that both materials have kept its original structural characteristics and exhibited high electrical conductivity when combined in nanocomposite form.
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)% (PPA1HT) to (55.1 ± 0.2)% (PPA16HT-HH). A broad halo in the PPA16HT-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 PPA1HT and PPA16HT-HH.
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.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.