Polymerization of aromatic nuclei. XXV. ESR and chemical studies on the radical cation nature of poly(p‐phenylene)

Abstract

SynopsisThe radical cation nature of poly(p-phenylene) (PPP) was examined by electron spin resonance (ESR) and chemical means. ESR studies revealed a radical concentration of 1.0 X 1021 spins/g for the crude polymer. Workup with aqueous acid decreased the value to 1.5 X loL8 spins/g. Reactions of the polymer with certain nucleophiles followed the half-regeneration mechanism, whereas with others, electron transfer mainly occurred. The origin of halogen in the polymer was found to arise from reaction of the radical cation with the oxidant, and not with halide during workup. Oxidation of PPP with various species increased the concentration of radical cations.

Suzuki Polycondensation: Polyarylenes à la Carte

“…In consequence, PPP was expected to exhibit mechanical and engineering properties similar to the other representative members of this class with the added advantage that it should be less hydrophilic, hydrolytically more stable and show a higher oxidative stability. Earlier attempts to synthesize PPP had started from benzene which was treated with Friedel-Crafts catalysts under oxidative conditions [22,23] (''Kovacic's method'');…”

Dehydro coupling of aromatic nuclei by catalyst-oxidant systems: poly(p-phenylene)

“…221 Since then a number of investigators have examined this property of the parent material, as well as related polymers. 18,19,187,202,204,[222][223][224][225][226][227][228] The observed unpaired electrons are highly delocalized and most likely have x-electron character. 224 Since the signal is a singlet which is devoid of fine structure, no detailed information is available.…”

Rubredoxin reductase from Alcanivorax borkumensis: Expression and characterization

“…Earlier attempts to synthesize PPP had started from benzene which was treated with Friedel–Crafts catalysts under oxidative conditions22, 23 (“Kovacic's method”); other methods made use of variations of the Ullmann reaction24 or the Wurtz–Fittig reaction 25. Further, an indirect method starting from a soluble precursor polymer which in a final step was converted into the insoluble PPP developed by Ballard et al26 needs to be mentioned.…”