Noncovalent functionalisation of polyaniline with the ionic liquid: An unneeded asset to prepare the emeraldine salt form of polyaniline using protic ionic liquids as polymerisation medium

Abstract

Since the properties of polyaniline (PANI) are widely related to the type of its dopant, the present manuscript has an objective to define whether and to what extent the protic ionic liquids contribute to doping PANI. Hence, pyrrolidinium p-toluenesulfonate [Pyrr][PTS] – a protic ionic liquid – has been investigated either as a polymerisation medium or as a secondary dopant. As for the polymerisation medium, it was found that binary mixtures of [Pyrr][PTS]/water, with different weight ratios, are convenient to prepare PANI in emeraldine salt form. Furthermore, the structural analysis of the resulted PANI has revealed that the cation of [Pyrr][PTS] does not functionalise PANI backbone and [Pyrr][PTS] acts like the typical Brřnsted acid in doping PANI, regardless of the amount of [Pyrr][PTS] in the polymerisation medium. To confirm this conclusion, [Pyrr][PTS] has also been studied as a secondary dopant: the conventional PANI has been prepared, deprotonated then dispersed into [Pyrr][PTS]/water with different formulations. The results have shown that [Pyrr][PTS] leads to the formation of reprotonated PANI without altering structural change. One can thus conclude that the noncovalent functionalisation of PANI with the cation of the protic ionic liquids is not an exigent requirement to prepare the emeraldine salt form of PANI in aqueous solutions of protic ionic liquids.

Keywords

• functional polymer
• conducting polymer
• nanocomposite
• conjugated polymer
• ionic liquid