In situ synthesis of polyoxadiazoles (POD) and carbon black (CB) as an approach to POD/CB nanocomposites

Pristine carbon black was oxidized with poly(phosphoric acid) to produce carboxyl groups. The carboxyl groups were consecutively treated with hydrazine sulfate to introduce arylcarbonyl and CONHNH2 groups. The groups on the CB surface were reacted with dicarboxylic acid to anchor the growing of polyoxadiazole chains. The properties of the bulk POD/CB composites were characterized by elemental analysis (EA), Fourier transform infrared (FTIR) and thermogravimetric analysis (TGA). The final composites were processed in films using a solution method aided by the use of a mini-calendar for final high shear mixing. Transmission electron microscopy (TEM), atomic force microscopy (AFM), dynamic mechanical thermal analysis (DMTA) and tensile tests were used to systemically characterize the high performance composite films. The POD composites with high molecular weight (in the order of magnitude of 105 g/mol) were soluble in polar aprotic solvents and stable at temperatures as high as 465 °C. The incorporation of the CB enhanced the overall mechanical properties of the composites at low CB content due to the presence of strong interfacial interaction between the polymer matrix and the filler.