This study addresses the thermal stability and degradation path of symmetric and asymmetric PS-b-PMMA block copolymers, widely employed to generate templates for nanopatterned materials, and of the associated P(S-r-MMA) random copolymers, through a combination of TGA and TGA–GC–MS techniques. The monomer evolution under isothermal and dynamic conditions was able to delineate the thermal degradation characteristics of all the copolymers. Although the temperature corresponding to the maximum of the main monomer loss is similar for the random and block copolymers, the onset of the main degradation for the random copolymers is observed at a temperature about 50 °C lower than the one for the block copolymers. In addition, the degradation profile of the random copolymers is highly asymmetrical in the low temperature side. This is partially due to the presence of TEMPO end groups, which …