Combination of Electrochemistry with Concurrent Reduction and Substitution Chemistry To Provide a Facile and Versatile Tool for Preparing Highly Functionalized Polyanilines

Various functional alkanethiols were found to be able to reduce polyaniline backbones from the emeraldine state 1 to the leucoemeraldine state 2, simultaneously derivatizing the backbones to form functionalized polyanilines. X-ray photoelectron spectroscopy (XPS) studies proved that these thiols formed sulfide bond linkages with the polyanilines backbones. This concurrent reduction and substitution chemistry, which was found to happen only at the diiminoquinoid rings, provided a novel and potentially interesting way to control the degree of substitution of polyanilines. Via this novel concurrent reduction and substitution chemistry, dodecylthio substituent group can be added onto the backbone of polyaniline to enhance its solubility in THF. Moreover, acid-containing thiols, e.g. mercaptoacetic acid and mercaptoethanesulfonic acid, can also be covalently attached to the polyaniline backbone to form two new types of self-doped polyanilines. By coupling the redox capability of an electrochemical cell and the concurrent reduction and substitution chemistry, the already modified and reduced polyaniline backbone can be reoxidized to restore the emeraldine state 1 . Additional cycles of concurrent reduction and substitution chemistry can be conveniently employed to further enhance the degree of substitution and/or the functionality. Via this new approach, polyaniline emeraldine base 1 has been sequentially derivatized with three different functional groups, i.e., dodecylthio, mercaptoacetic acid, and mercaptoethanesulfonic acid, on the same backbone.