The synthesis of polysulfide polymers with unsaturated and saturated units in the backbone and their characterization by Fourier transform infrared, NMR, gel permeation chromatography, thermogravimetric analysis, and differential scanning calorimetry are reported. This is the first report on an analysis of the thermal degradation of an unsaturated polysulfide polymer [poly(2-butene sulfide)] carried out by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). A unique phenomenon of exothermic degradation has been detected by differential thermal analysis and has been attributed to the energetics of the unsaturated polysulfide linkage during degradation. The thermal degradation products studied by Py-GC/MS indicate that the formation of sulfur-containing products is more favored than the formation of nonsulfur-containing products. Furthermore, a comparative study of the thermal degradation of unsaturated and saturated polysulfide polymers has been conducted with thermogravimetry and Py-GC/MS analyses. These analyses have shown that the mechanisms of degradation of these polymers are different, and the lower number of pyrolysis products indicates a selective cleavage of the polymer during degradation in the saturated polysulfide polymers. (C) 2004 Wiley Periodicals, Inc.