Synthesis and characterization of poly(benzobisoxazole)s and poly(benzobisthiazole)s with 2,2′-bipyridyl units in the backbone

This paper reports the synthesis and physical properties of a series of novel bipyridine-containing poly(benzobisoxazole)s and poly(benzobisthiazole)s. The polymers were synthesized by polycondensation of 2,2'-bipyridine-5,5'-dicarboxylic acid with diaminobenzenediols in poly(phosphoric acid). Some model compounds were also synthesized by a similar approach for comparison. The polymers exhibited extremely high thermal stabilities in air or nitrogen atmosphere. From the polarized microscopic studies, lyotropic mesophases were observed in some polymer solutions in methanesulfonic acid. The 2,2'-bipyridyl moieties on the polymer main chain were able to form metal complexes with bis(2,2'-bipyridyl)ruthenium(II) compounds, which was proved by different characterization methods such as electronic and luminescence spectroscopy, cyclic voltammetry, and thermal analysis. The charge carriers mobilities of the polymer metal complexes are of the order of 10(-5) cm(2) V-1 s(-1), which are 2 orders of magnitude higher than that of the metal-free polymers. This clearly shows that the ruthenium complexes can play the role as charge carriers in the charge transport process.