Oxidation of Aniline with Silver Nitrate Accelerated by p-Phenylenediamine: A New Route to Conducting Composites

• Published in: Macromolecules 2010-12, Vol.43 (24), p.10406-10413
• Main Authors: Bober, Patrycja, Stejskal, Jaroslav, Trchová, Miroslava, Prokeš, Jan, Sapurina, Irina
• Format: Article
• Language: English
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma101474j

The reaction between two nonconducting compounds, aniline and silver nitrate, yields a composite of two conducting products, PANI and silver. While the oxidation of aniline with silver nitrate is slow and takes over several months, the addition of a small amount of p-phenylenediamine, 1 mol % relative to aniline, shortens the reaction time to a few hours and, with higher concentrations of p-phenylenediamine, even to tens of minutes. Nonconducting aniline oligomers, however, are also present in the oxidation products as a rule. The chemistry of individual oxidation pathways is discussed. Higher concentrations of p-phenylenediamine in the reaction mixture with aniline give rise to copolymers, poly[aniline-co-(p-phenylenediamine)]s, and their composites with metallic silver. p-Phenylenediamine alone can similarly be oxidized with silver nitrate to poly(p-phenylenediamine) composite with silver. Silver is present in the composites both as nanoparticles of ∼50 nm size and as larger objects. The composites have conductivity in the range of the order of 10−3−103 S cm−1 at comparable content of silver, which was close to the theoretical expectation, 68.9 wt %. The composites prepared in 1 M acetic acid always have a higher conductivity compared with those resulting from synthesis in 1 M nitric acid. The polymerizations of aniline accelerated with 1 mol % of p-phenylenediamine in 1 M acetic acid yield a composite of the highest conductivity, 6100 S cm−1. At higher contents of p-phenylenediamine, poly[aniline-co-(p-phenylenediamine)] composites with silver have a conductivity lower by several orders of magnitude. The oxidation of p-phenylenediamine alone with silver nitrate in 1 M acetic acid also yields a conducting composite, its conductivity being 1750 S cm−1. The semiconductor type of conductivity in polymers and the metallic type of conductivity in silver may compensate to yield composites with conductivity nearly independent of temperature over a broad temperature range.