New azophenol polymers (P-1, P-2 and P-3) were synthesised by the oxidative polycondensation (OP) reaction of three different azophenol monomers in aqueous alkaline medium with NaOCl as the oxidant. The monomers and the polymers were characterised by elemental analyses, and UV-visible, Fourier transform infrared, H-1 NMR and C-13 NMR spectroscopic studies, which revealed that the polymers synthesised by OP are composed of oxyphenylene (C-O-C) and phenylene (C-C) units. The polymers obtained are soluble in dimethylformamide and dimethylsulfoxide. Average molecular weights of the polymers were determined by gel permeation chromatography. Additionally, P-2 and P-3 are soluble in water and methanol. On the basis of thermogravimetric analyses, 5 and 50% weight-loss temperatures of the polymers were found to be 218, 700 (P-1), 263, 609 (P-2) and 100, 809 degrees C (P-3), respectively, suggesting a high thermal stability. Thermal analyses using differential scanning calorimetry revealed that the azophenol polymers are highly amorphous, and melting peaks were not observed in the heating cycles. This suggests that all the polymers are highly amorphous. The azophenol polymers show a reversible trans-cis-trans isomerisation process. These properties of the polymer could be promising for their technological usage. (C) 2007 Society of Chemical Industry.