Hybrid materials of polyaniline and acidic hexaniobate nanoscrolls: high polaron formation and improved thermal properties

Abstract

The study of hybrid materials of components combined in the nanoscale range is an active field due to the possibility of new technologically relevant applications. This paper reports the structural characterization and investigation of the thermal properties of a new hybrid material formed by the mixture of dispersions of polyaniline (PANI), a conducting polymer, and acidic hexaniobate nanoscrolls (NbONsc), a semiconducting metal oxide. Resonance Raman spectra indicate that the relative population of polaronic to bipolaronic segments in the hybrid material prepared at pH 2.5, is higher than indicated for pristine PANI prepared in 1.0 mol L⁻¹ hydrochloric acid. Although the hybrid material was prepared at pH 2.5, electron paramagnetic resonance spectra indicate similar polaron populations compared with pristine PANI, which indicate that the hybrid material presents high conversion of bipolaronic to polaronic segments. Such features were attributed to a strong interaction between the PANI and the acidic NbONsc, inducing conformational changes of the polymeric chains and high formation of polarons at pH 2.5 (secondary doping). Thermogravimetric analyses showed that the onset temperatures of polymer decomposition in the hybrid materials are ca. 15 °C higher compared with pristine PANI. More interestingly, RR spectroscopy data showed that PANI in the presence of NbONsc remains in its doped form even after heating at 150 °C for 90 min, which was not observed for the pristine polymer. Based on a simple experimental procedure reported here, thermally stable hybrid nanomaterials of highly doped PANI and acidic hexaniobate nanoscrolls were successfully prepared and characterized and exhibit potential applications for electronic devices.