Study on the influence of the morphology in the properties of the emeraldine salt and base forms of pure polyaniline and its composites with gold nanostructures

Author(s)

Marcelo Medre Nobrega

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ)
• Defense date: 2014-11-19

Examining board members

Marcia Laudelina Arruda Temperini; Vera Regina Leopoldo Constantino; Luiz Henrique Dall'Antonia; Italo Odone Mazali; Susana Ines Cordoba de Torresi

• Advisor: Marcia Laudelina Arruda Temperini

Abstract

This thesis presents a study on the influence of the morphology (bulk and nanofibers) in the behavior of the doped (PANI-ES) and dedoped (PANI-EB) forms of polyaniline (PANI) to different perturbations, such as heating and high pressure, monitoring the materials responses by Raman and infrared spectroscopies. Other techniques such as mass spectrometry coupled-thermogravimetry analysis (TGA-MS) and scanning electron microscopy (SEM) were used to complement the characterization and support the results. In addition to pure PANI, PANI composites containing gold (Au) nanoparticles were synthesized and characterized and the interaction of PANI-ES with different gold nanostructures was also studied by SERRS technique. A difference in the thermally induced segments (aromatic or non-aromatic) was reported, formed by cross-links depending on the PANI form (PANI-ES or PANI-EB). Furthermore, the morphology played an important role in the thermal behavior of the polymers, nanofibers of PANI-ES were more resistant to dedoping process than its bulk counterparts. Considering the high pressure effect, the results showed a reaction on PANI-EB starting at ca. 9 GPa and, in this reaction, the morphology played no important role, up to pressures of 15 GPa. For PANI-ES, the occurrence of some spectral changes was observed after decompression of the system, suggesting the dedoping and cross-linking reaction induced by pressure. PANI-Au composites presented PANI in its conducting form and the results suggested that its electroactivity and capacitance were enhanced. Finally, the investigation of the interaction of PANI with Au nanoparticles showed that PANI is an excellent molecule to evaluate the performance of SERRS substrates excited at 1064 nm, due to PANI\'s high stability and the possibility of evaluating almost exclusively the contribution of the electromagnetic mechanism acting in SERRS enhancement. (AU)

• FAPESP's process: 10/18107-8 - Study of the structures of PANI nanofibers and their hybrids with metallic nanostructures by Raman epectroscopy
• Grantee: Marcelo Medre Nobrega
• Support Opportunities: Scholarships in Brazil - Doctorate