Investigation of physical properties and structure–property relationship in new poly(azo-sulfone-amide)s

Series of aromatic polyamides containing azo groups have been synthesized by the phosphorylation polycondensation of a new dicarboxylic acid ( E)-1-(4-(4-(3-carboxypyridylazo)thiocarbamoylaminophenyl-sulfonyl)phenyl)-3-(3-carboxypyridylazo)-thiourea and various diamines. Poly(azo-sulfone-amide)s (PASAs) were characterized using spectroscopic techniques, solubility, molar mass, electrical conductivity, mechanical strength, nonflammability, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) studies. PASAs possessed fine solubility in polar solvents and high molar mass 70 × 103–75 × 103 gmol−1. These polyamides showed fibrous structure according to field-emission scanning electron microscopy (FESEM). Thermal and nonflammability data indicated that PASAs were fairly stable above 500°C having initial weight loss of around 525–531°C, 10% of gravimetric loss in the range of 542–563°C, own high glass transition temperature 257–267°C and limiting oxygen index (LOI) values (35–47%). The polymers also demonstrated higher tensile strength (61.10–74.29 MPa) and elongation at break (1.49–1.57). FESEM images displayed fibrous morphology of the PASAs. Moreover, polyamides showed superior electrical conductivity (1.45–1.92 S cm−1). Fine balance of the properties render the new PASAs potential engineering plastics for a number of aerospace relevance.