The degradation and prestabilization of polyacrylonitrile (PAN) were investigated with differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR). The initial temperature, initial loss-weight temperatures, and loss-weight were significantly lowered when ammonium itaconate (AIA) was used as comonomer. One exothermal peak of PAN (homopolymer) was shown in the DSC curves, while there were four exothermal peaks of poly(AN-AIA). FTIR spectra results confirm the degradation process of NH4+ groups. During the heating process, NH4+ groups (3030 cm(-1)) were changed into NH3+ (2955 cm(-1)) and then NH2+ groups (2920 cm(-1)). The dissociated H+ could initiate the cyclization reactions of C equivalent to N companied with heat released. The effect of ammonia on degradation and prestabilization of PAN was also studied. It was found that ammonia could accelerate prestabilization of acrylic precursors. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 117: 1596-1600, 2010