Series of infrared spectra were recorded of chars produced by heating a pure bisphenoI-A polycarbonate resin (PC) in vucu5 at successively increasing temperatures, up to 750ยฐC. FI-IR photothermal beam deflection spectroscopy was used. PC, after remaining essentially intact over a wide range of temperatures, underwent massive and dramatic changes upon heating in a narrow temperature interval (440-490ยฐC). Thermal branching and cross-linking occurred near 440ยฐC with the formation of diary1 ether, ester and unsaturated hydro~ar~na~ous bridges. Small, still discrete aromatic entities were formed on pyrolysis above 490ยฐC. Fusion of the aromatic rings into larger polyaromatic structures, however, occurred to a significant extent only at 59O"C, when the polymeric network collapsed completely; all aliphatic bridges were destroyed and the oxygen bridges were incorporated in the polyaromatic domains which were formed. The resulting char was similar to other intermediate temperature chars. The continuum of the carbon absorption extends throughout the spectral region at 750ยฐC. Key Wor&-Infrared spectra, polycarbonate, thermal degradation, carbonization, polycarbonate chars, ph~tothe~al spectrostkpy, carbon.