Interactions between polyaniline and methanol vapour

UV–VIS spectroscopy, electron spin resonance spectroscopy (ESR) and conductivity measurements have been used to characterise the interactions between methanol vapour and polyaniline. The data indicates that the methanol hydrogen bonds to two locations on the emeraldine base such that it is able to form a bridge between the polymer chains causing twisting. This prevents the few remaining polarons from moving beyond a few monomer units, effectively localising them, giving rise to a decrease in conductivity and an increase in absorption at ca. 1.6 eV. However, in the case of the emeraldine salt protonation of the quinoid moieties’ nitrogen restricts the number of potential hydrogen bonding sites, preventing the methanol from forming a bridge between two polymer chains. At the same time, the high conductivity of the emeraldine salt allows the charge that is transfer to the polyaniline, as a result of the hydrogen bonding to the methanol, to be distributed along the conjugated chain in the form of polarons and bipolarons.