A Schiff base monomer was synthesized by the condensation reaction between salicylaldehyde and ethylenediamine. The Schiff base polymer, with a double azomethine group, was prepared by oxidative polycondensation (OP) reaction of monomer in aqueous alkaline medium with NaOCl as an oxidant at 90 degrees C. The monomer and polymer were characterized by UV-Vis, FT-IR, H-1-and C-13-NMR spectroscopic studies, which revealed that the polymer synthesized by OP is composed of oxyphenylene (55%) and phenylene (45%) units. The polymer was soluble in aqueous alkaline, THF, DMF and DMSO. The thermal properties of monomer and polymer were evaluated by differential thermal analysis (DTA) and thermogravimetric (TG) analyses. According to TG, the 5% and 50% weight loss temperatures of the polymer were 200 degrees C and 800 degrees C, respectively.