The Infrared Spectrum of Polypyrrole–T2O System

Abstract

The infrared spectra of polypyrrole contacting with T 20 gas were observed for ca. l00days. After adding T 2 0 (1.2 Ci; isotopic purity: 15%) the band at 2180cm-1 was observed, which is assigned to the N-T stretch. Although the bands at 1560 and 1204 cm-1 were initially strong, they became relatively weak by T P-irradiation. On the other hand, the bands at 1655 and 1400 cm-1 as well as 1700 cm-1 became relatively strong by T Pirradiation. These are explained in terms that the quinonoid-type structure with partially the aromatic-type structure decreases and the structure with probably C = N bonds is formed. It was also found that many carbony defects are formed in both the atmosphere and T P-radiolysis. KEY WORDS Polypyrrole / T /3-Radiolysis / Infrared Spectrum/ Tritium We have studied T /3-radiolysis for such systems as poly(vinyl alcohol) by means of infrared spectroscopy. 1-4 The method is quite useful for clarifying structural changes and decomposed species which _ result from T /3-radiolysis. In the present study we will report the infrared spectra of polypyrrole (PPy)-T 2 0 system, drawing the structural change by T /3-irradiation. PPy prepared by electrochemical oxidation of pyrrole in the presence of inorganic salts includes counter anions as dopant. This is true for PPy prepared by chemical oxidation. That is, doped PPy has cation defects, so-called polaron and bipolaron, which play important role in electronic conductivity. The vibrational study of PPy 5-14 has been widely carried out in relation to the structural change accompanying with electrochemical redox. On the other hand, the infrared spectra of doped PPy 5-11 reveal quite complex features that they depend on the method of oxidation and the kinds of dopant and their concentrations. The similar feature is also seen in reduced PPy. 5 • 7 • 10 • 11 It is also reported 7 • 10 that carbonyl groups, C = N bonds and sp 3 C-H bonds are formed.