Structure of the soluble Lewis acid poly(p-phenylenebenzobisthiazole) and poly(p-phenylenebenzobisoxazole) complexes

The published postulated structures of the species present in aluminum chloride containing nitromethane solutions of PBZT and PBO have been reinvestigated. Consideration of previously reported and new Al-27 NMR spectra indicate that the predominant species in solution are AlCl4- and a cationic species containing aluminum bound to the nitrogen atoms in the polymer repeat unit, which are formed by reaction of the neutral aluminum chloride complexed polymer. Calculational evidence is also presented to support a 2:1 ratio of aluminum chloride to polymer repeat unit in the neutral complex.