Novel phosphazene cyclomatrix network polymers were synthesized via nucleophilic displacement of activated nitro groups of tri(4-nitrophenoxy)tri(phenoxy)cyclotriphosphazene and hexa(p-nitrophenoxy)cyclotriphosphazene with the hydroxyls of bisphenol A. Both the monomers and polymers were characterized by Fourier transform infrared (FTIR) and H-1-NMR spectroscopy, and their structures were identified. The thermal and flame-retardant properties of the polymers were investigated with thermogravimetric analysis in air, pyrolysis, and combustion experiments. Both solid and gaseous degradation products were collected in a pyrolysis process and analyzed with FTIR spectroscopy, gas chromatography/mass spectrometry, and scanning electron microscopy. The results demonstrated that the cyclomatrix phosphazene polymer would have excellent thermal stability and flame-retardant properties if it could form a crosslinked phosphorous oxynitride structure during pyrolysis or combustion. A flame-retardant mechanism of "intumescent" was proposed to elucidate the pyrolysis and combustion process. (C) 2004 Wiley Periodicals, Inc.