Electronic conduction in polymers. IV. Polymers from imidazole and pyridine

Abstract

The pyrolysis of 2,4,5-triiodoimidazole and 1,2,4,5-tetraiodoimidazole yields polymers whose poor conductivity is attributed to the presence of two types of nitrogenous centres with electron-donating and electron-accepting properties respectively. Nitrogenous polymers produced by passing mixtures of chlorine and pyridine through a silica tube heated to 800° have low resistivities (0.03 to 15 ohm cm), indicating that the polymers have a highly conjugated structure. The increase of resistivity with chlorine content, together with the decrease in resistivity observed on adsorption of the electron donor ethylene, suggest that the nitrogen centres are donor rather than acceptor type. The properties of the polymers suggest that the latter are probably substituted polypyridines. The results support the following guide to synthesis: organic polymers of good conductivity can be prepared by directly crosslinking small aromatic or heterocyclic units into three-dimensional non-planar structures in which the number of crosslinks should be as large as possible. Either electron-donating or electron-accepting structures, but not both, may be present in the one polymer.