On the molecular recognition and associations between electrically conducting polyaniline and solvents

Abstract

The specific interactions between sulphonic acid protonated polyaniline (PANI) and solvents are here studied both by the semiempirical AM1 method and experimentally. Phenolic solvents are shown to have a relatively large interaction with the sulphonate anions of the counterions and with the amines in PANI. In addition, a properly functionalized counterion may form cyclic associations provided that there is a steric match between the molecules concerned. This concept is called molecular recognition and it is a novel concept in the context of PANI. For example, the carbonyl group in (±)-10-camphor sulphonic acid (CSA) can form a hydrogen bond to the hydroxyl group of m-cresol, whereby the phenyl ring becomes coplanar with one of the PANI rings thus enabling enhanced van der Waals interaction. This additional specific interaction agrees with our observed increased solubility with CSA doped PANI in m-cresol, compared to its solubility in dimethyl sulphoxide or chloroform, or to tosylene sulphonic acid doped PANI in m-cresol. The above cyclic associations are suggested for dilute solutions and for the amorphous domains of solid films. In the latter case, they provide a potential mechanism to yield planar conformation in the crystalline domains: during the evaporation of m-cresol, stacking to crystal structure may twist the rings due to the planar m-cresol molecules on top of PANI rings. This is in agreement with the observed high conductivity. The present results indicate that computational methods combined with the concept of molecular recognition may open new possibilities to tailor the rigidities and solubilities of macromolecules.

Conductive blends of polyaniline with plasticized poly(methyl methacrylate)

“…17 In the case of a three-components system PANI-dopant-mcresol, it is possible to predict electrical transport properties of the processed films by the investigation of UV-vis-NIR spectra of the solution used for casting. 18 If due to specific solvent-dopant interactions, 19,20 a conformation favoring the delocalization of charge carriers (polarons) is achieved, the spectrum shows one localized peak at 440 nm and a monotonically increasing absorption, which starts at approximately 500 nm and extends into NIR. Chain conformation, leading to localized polarons, gives rise to three well-defined absorption peaks at 360, 430, and approximately 900 nm.…”

Theoretical study of the structure and electronic spectra of fully protonated emeraldine oligomers

“…The theoretical investigations dedicated to PANI are also plentiful and cover almost all computational levels, i.e., molecular mechanics and dynamics [17] (doping mechanism, proton migration, temperature dependence of absorption, and conductivity), Monte Carlo [18,19] (interchain electronic transport in disordered systems), Hü ckel [20] (band structure, DOS), semi-empirical methods [21,22] (structure, UV/VIS spectra), as well as firstprinciple methods such as Hartree-Fock and DFT [23][24][25][26][27][28] (structure, infrared and Raman spectra). Some semi-empirical calculations are performed for the evaluation of torsion barriers and solvation effects on the UV/VIS spectra of PANI chains, accounted for by models including 2 to 4 solvent molecules [29,30]. The main part of these computations was performed for species with artificially augmented symmetry by means of end-capping of the chains with identical residues.…”

Investigation of Electrochemical Copolymerization of 1‐Naphthylamineaniline in the Presence of Various Organic Sulfonic Acids

“…Ikkala et al have reported that a hydrogen bond can be formed between two of the oxygens in the sulfonic acid group (SO 3 -) and the hydrogen in the polymer backbone, causing a homogeneous doping and higher conductivity than HCl doped. 19 Increasing the sequence of current intensity for homo and copolymerization in the pres- With considering the redox peaks of PNPA with its copolymers, it is clear to see that oxidation occurred at a higher potential with larger DEp in comparison with copolymers. The changes in Ep and DEp for the copolymerization involving NPA and ANI indicate that NPA unites have different structural environments in the copolymer in contrast to PNPA.…”