Studies on the resonance Raman spectra of polyaniline obtained with near‐IR excitation

Abstract

The effects of near-IR (NIR) laser power over the Raman spectra of poly(aniline) emeraldine salt (PANI-ES) and base (PANI-EB) were investigated. The reasons for the existence of several bands from 1324 to 1500 cm −1 in the Raman spectra of poly(aniline) obtained at NIR region were also studied. The bands from 1324 to 1375 cm −1 were associated to nC-N of polarons with different conjugation lengths and the bands from 1450 to 1500 cm −1 in Raman spectra of PANI emeraldine and pernigraniline base forms were correlated to nC N modes associated with quinoid units having different conjugation lengths. The increase of laser power at 1064.0 nm causes the deprotonation of PANI-ES and the formation of cross-linking segments having phenazine and/or oxazine rings. For PANI-EB only a small spectral change is observed when the laser power is increased, owing to the low absorption of this form in the NIR region.

Thermal diffusivity measurements in PANI and PANI-MWNT composites using photo acoustic technique

“…All the characteristic Raman frequencies of PANI (HCl) and PANI (HCl)-MWNT composite are observed in the spectra [8][9][10]. The characteristic D-mode and G-mode vibrations of MWNT are observed in the composite at 1574cm -1 and 1345cm -1 respectively, confirming the formation of the composite.…”

Spectroscopy of Polyaniline Nanofibers

“…On the other hand, (Quillard et al, 1995) proposed that this band was not correlated with protonated segments but with over-oxidized segments such as those present in PANI as the pernigraniline base (PANI-PB). Some controversial aspects about the Raman spectra of poly(aniline) obtained at NIR radiation excitation were recently re-examined by (Do Nascimento & Temperini, 2008). The bands from 1324 to 1375 cm -1 were associated to νC-N of polarons with different conjugation lengths and with the presence of charged phenazine-like and/or oxazine-like rings in PANI-ES as chemically prepared.…”

Nanodiamond-mediated crystallization in fibers of PANI nanocomposites produced by template-free polymerization: Conductive and thermal properties of the fibrillar networks

“…The wavenumber of this mode is sensitive to electron delocalization around the CwNwC part of the polymer backbone and it is typically lower for a more delocalized structure, i.e. radical segments with a larger conjugation length [25,26]. Comparing the position of this mode in the spectra obtained with the red and NIR lines, it seems that PANI in the composite fibers is characterized by polarons with conjugation lengths slightly shorter than in the pure polymer.…”