AbstractA series of polyoxadiazoles (PODs) based composites containing carbon black (CB) are prepared through a fast polycondensation reaction of hydrazine sulfate and dicarboxylic acid monomers using poly(phosphoric acid) (PPA) as reaction medium. In order to achieve a homogeneous dispersion of CB, a predispersion step is applied to the CB prior to the synthesis. The moderate acidic nature and high viscosity of the PPA medium promote the oxidation of the CB and suppress reaggregation after dispersion. The carboxylic groups generated on the surface of the CB effectively anchored the growing of POD chains, improving the interfacial interaction between the CB and the surrounding matrix. An increase of 22% in storage modulus at 100 °C is observed. The tensile strength increases up to 48% with the CB addition and the elongation at break increases up to 118% at a low concentration of CB (0.5 wt.-%). The resultant CB/POD composites, which can be cast as dense films, are soluble in several polar aprotic solvents and their POD matrix have molecular weights in the range of 105 g·mol−1. The high-performance, high-temperature light-weight materials obtained are thermally stable at temperatures as high as 450°C.