The oxidative polycondensation reaction conditions and optimum parameters of o-phenylazomethinephenol (PAP) with oxygen (air) and NaOCl were determined in an aqueous alkaline solution at 60-98degreesC. The properties of oligo-o-phenylazomethinephenol (OPAP) were studied by chemical and spectra analyses. PAP was converted to dimers and trimers (25-60%) by oxidation in an aqueous alkaline medium. The number average molecular weight (Mu), mass average molecular weight (M-w), and polydispersity index (PDI) values were 1180 g mol(-1), 1930 g mol(-1), and 1.64, respectively. According to these values, 20-33% of PAP turned into OPAP, During the polycondensation reaction, a part of the azomethine (-CH=N-) groups oxidized to carboxylic (-COOH) group. Thus, a water-soluble fraction of OPAP was incorporated in the carboxylic (-COOH); (2-20%) group. Also, the structure and properties of oligomer-metal complexes of OPAP with Cu(II), Ni(II), Zn(II), and Co(II) were studied. Antimicrobial activites of the oligomer and its oligomer-metal complexes were tested against B. cereus, L. monocytogenes, B. megaterium, B. subtilis, E. coli, Str. thermophilus, M. smegmatis, B. brevis, E. aeroginesa, P. vulgaris, M. luteus, S. aureus, and B. jeoreseens. Also, according to differential thermal analysis and thermogravimetric analysis, OPAP and its oligomer-metal complexes were stable throughout to temperature and thermooxidative decomposition. (C) 2002 Wiley Periodicals, Inc.