The material combining conducting polymer and ionic liquid: Hydrogen bonding interactions between polyaniline and imidazolium salt

New type of interaction between polyaniline and ionic liquid leading to conducting polyaniline form is reported. Blue non-conducting polyaniline base was exposed to ionic liquid, 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, and changed its colour to green. This was associated with the increase in conductivity by ten orders of magnitude from 6 × 10−11 S cm−1 to 0.43 S cm−1. The FTIR spectroscopic analysis suggests that (1) hydrogen bonding of hydrogen in imidazolium heterocycle with imine nitrogen in polyaniline combined with (2) hydrogen bonding of amine groups in polyaniline to oxygen atoms in trifluoromethanesulfonate anion are responsible for the observed effects. The quantum-chemical calculations of the corresponding hydrogen bonding interactions support this concept. The thermogravimetric analysis demonstrates improved thermal stability of the material compared with a standard polyaniline hydrochloride.