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

Molecules

Jaqueline de Araújo Bezerra¹  Pedro Henrique Campelo²  Hidembergue Ordozgoith da Frota³  Henrique Duarte da Fonseca Filho³  Douglas de Souza Gonçalves⁴  Adriano de Souza Carolino⁵  Matheus Moraes Biondo⁵  Edgar Aparecido Sanches⁵  Lilian Rodrigues de Oliveira⁵  Jéssica Montenegro Santana da Silva⁵  Ştefan Ţălu⁶ 

[1] Analytical Center, Federal Institute of Education, Science and Technology of Amazonas (IFAM), Manaus 69020-120, AM, Brazil;Department of Food Technology, Federal University of Viçosa (UFV), Viçosa 36570-900, MG, Brazil;Graduate Program in Materials Science and Engineering (PPGCEM), Faculty of Technology, Federal University of Amazonas (UFAM), Manaus 69067-005, AM, Brazil;Graduate Program in Physics (PPGFIS), Federal University of Amazonas (UFAM), Manaus 69067-005, AM, Brazil;Laboratory of Nanostructured Polymers (NANOPOL-@nanopol_ufam), Federal University of Amazonas (UFAM), Manaus 69067-005, AM, Brazil;The Directorate of Research, Development and Innovation Management (DMCDI), Technical University of Cluj-Napoca, 15 Constantin Daicoviciu St., 400020 Cluj-Napoca, Romania;

关键词: heat treatment;    poly(o-methoxyaniline);    XRD;    Le Bail method;   

DOI  :  10.3390/molecules27123693

来源: DOAJ

【 摘 要 】

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.

【 授权许可】

Unknown