XPS Study of Highly Sulfonated Polyaniline

Highly sulfonated polyaniline prepared via a synthetic scheme using leucoemeralding base (LEB−SPAN) has been studied using X-ray photoelectron spectroscopy (XPS). A sulfonation level (S/N ratio) as high as 0.80 ± 0.10 has been revealed in XPS analysis, agreeing well with the element chemical analysis results (∼0.78). This contrasts to an S/N ratio of 0.50 for SPAN made via the earlier reported synthetic method. The detailed S 2p and N 1s peak analyses both show that the oxidation level is ∼50%, implying a better thermal stability of emeraldine oxidation state over those of leucoemeraldine and pernigraniline oxidation states. These XPS analysis results are supported by UV−vis and FT-IR analysis results. The method of resolving 2p3/2 and 2p1/2 peaks in the S 2p spectrum is discussed.