Vibrational analysis of heterocyclic polymers: A comparative study of polythiophene, polypyrrole, and polyisothianaphtene

Abstract

We present for the first time a comparative vibrational study of polythiophene, polypyrrole, and polyisothianaphthene. The calculation is performed at k=0 in the plane of the chains for both aromatic-like and quinoid-like structures. The Ag species which are present in the Raman spectra are more particularly investigated. The frequency changes, the atomic displacements, and the influence of the interring distance r and the interring force constant F(r2) are analyzed when the quinoid character is varied. We demonstrate that the ring linkage vibrations C–C or C=C give frequencies in the range 1450–1800 cm−1. It is found that a similar dependence of these frequencies on F(r2) and r exists for all the forms except for aromatic polyisothia naphthene. Also, analogies between the three polymers in the experimental Raman spectra are evidenced. Refined sets of force constants very close to those of the monomers are suitable for explaining the main features of these spectra and can be used to determine the degree of aromaticity and the degree of bond alternation.

Theoretical Modeling of the Doping Process in Polypyrrole by Calculating UV/Vis Absorption Spectra of Neutral and Charged Oligomers

“…[49][50][51] In the oligomer studies the issue of bipolaron formation was not addressed and the interpretation of polymer results remains controversial. 8,12,13,16,17,20,22,23,25,[52][53][54][55] Electronic structures of PPy and OPs have been investigated theoretically before; 20,[56][57][58][59][60][61][62][63][64][65][66][67][68][69][70] however, we are not aware of calculations of absorption spectra during the doping process of pyrrole oligomers or polymers. We have recently calculated such spectra for polyenes 71 and OTs.…”

Double corrosion protection mechanism of molybdate-doped polypyrrole/montmorillonite nanocomposites

“…The spectra associated with the oxidised PPy are characterised by a very large adsorption band located in the spectral domain between 4000 and 2500 cm À1 , which is characteristic of the OH groups belonging to residual water molecules trapped in the polymer matrix as well as water molecules absorbed in the hydrophilic MMT. This result has already been observed in the case of PPy electrosynthesised in aqueous sodium tartrate [16], and some solids containing water of crystallisation, corresponding to the so-called 'lattice water' [16]. In comparison with the wellknown IR spectrum of PPy obtained in organic media on noble metal electrodes such as Pt, all the PPy characteristic bands are observed in the spectra.…”

“…The bands situated at 915 and 795 cm À1 are attributed to the out-of-plane vibration of the C-H bonds. The band at 1121 and 1034 cm À1 in the spectra is attributed to the in-plane deformation of the C-H bonds [16]. The stretching Table 2 gives the assignments of some Raman bands and compares the frequencies of the various vibration modes collected on the PPy/Ag spectra and with those theoretically calculated by Faulques et al [16,17].…”

“…The band at 1121 and 1034 cm À1 in the spectra is attributed to the in-plane deformation of the C-H bonds [16]. The stretching Table 2 gives the assignments of some Raman bands and compares the frequencies of the various vibration modes collected on the PPy/Ag spectra and with those theoretically calculated by Faulques et al [16,17]. According to the theoretical values reported by Faulques et al [16,17], the vibration frequency of the C¼C bond of the PPy in the oxidised form (at 1593 cm…”

Layers of Inhibitor Anion – Doped Polypyrrole for Corrosion Protection of Mild Steel

“…Figure 22 presents the Raman spectrum of PPy/MMT nanocomposite measured at 514 nm with 1 mW laser power. Table 1 gives the assignments of some Raman bands and compares the frequencies of the various vibration modes collected on the PPy/Ag spectra and with those theoretically calculated by Faulques et al [55]. According to the theoretical values reported by Faulques et al [55], the vibration frequency of the C=C double-bond of the PPy in the oxidized form (at 1593 cm -1 ) is greater than that in the reduced form (Table 1).…”