The polymerization of aniline intercalated into montmorillonite clay was monitored by in situ UV−vis−NIR and resonance Raman spectroscopies and in situ small-angle X-ray scattering. In the initial stages of the polymerization, it is observed the PANI−ES polaronic band at 750 nm in the UV−vis−NIR spectrum and also the characteristic PANI-ES resonance Raman spectrum (excited at 632.8 nm), which indicate that the head-to-tail coupling reactions between anilinium radical cations are occurring. Nevertheless, the resonance Raman spectrum excited at 488.0 nm presents bands at 1211, 1370, 1455, and 1608 cm-1, assigned to the benzidine dication species, which suggests that tail-to-tail coupling reactions are also occurring. In the final stages of polymerization, the presence of electronic absorption bands at 670 and 620 nm indicates the formation of new chromophoric species, which is also confirmed by its peculiar resonance Raman spectrum at 632.8 nm wavelength. The in situ SAXS results show that, during the anilinium polymerization in aqueous clay suspension, the interlayer spacing is ca. 19 Å. XRD diffraction pattern and SEM images of the powder PANI−MMT nanocomposites indicate that the polymerization occurs mainly between the clay layers, and the basal spacing is ca. 13.2 Å. While the IR spectra of nanocomposites show only bands due to PANI−ES-like segments, resonance Raman and nitrogen XANES techniques lead to the presence of PANI−ES-like chains, benzidine segments, azo bonds, and phenazine-like rings in the structure of the confined conducting polymers. The XPS technique detects only PANI−ES segments of the polymeric structure, suggesting that on the external surface and/or on the edge of clay crystal they are predominant in the chains.

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.

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Changes in poly(diphenylamine) chains primarily doped with camphorsulfonic acid (PDPA-CSA) during the secondary doping process were spectroscopically characterized. The UV−vis−NIR spectrum of PDPA-CSA treated with m-cresol showed the NIR (1100 nm) tail of the band due to free-carrier absorption, confirming the increase of polymer conductivity. Resonance Raman and ESR results showed that, during this treatment, there was a conversion of diphenosemiquinone segments into diphenoquinoid ones. These results indicated that spinless species are the free carriers in this kind of polymer, which are in contrast with those observed for PANI-CSA treated with m-cresol. The thermal behavior of PDPA-CSA was also studied by in-situ resonance Raman and ESR spectroscopies. These results also indicated a conversion of diphenosemiquinone segments into diphenoquinoid ones. New bands in Raman spectra at high temperature presented by PANI and PDPA were assigned to oxidized structures having oxazine-like rings.

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