X-ray Photoelectron Spectroscopy Study of Counterion Incorporation in Poly(3,4-ethylenedioxythiophene)

Poly(3,4-ethylenedioxythiophene) (PEDOT) is widely used in organic electronics and biomaterial coatings because of its outstanding electrical properties and chemical stability. In this research, X-ray photoelectron spectroscopy (XPS) was used to investigate incorporation of different counterions during electrochemical polymerization into PEDOT. The counterions probed included both a polyanion, poly(sodium 4-styrenesulfonate) (PSSNa), and small anions including lithium perchlorate, sodium chloride, and sodium phosphate monobasic monohydrate. In addition to these counterions, an ion mixture, phosphate-buffered saline solution (PBS), was also examined. For such mixtures, the chlorine anion from sodium chloride was found to act as the counterion during PEDOT electrochemical polymerization in PBS solution. This is important because PEDOT is being considered for biomedical applications, which may be prepared in the presence of PBS or other mixtures of ions. Various mixtures of PSSNa, lithium perchlorate, sodium...