Properties such as miscibillity, interaction and the thermal degradation behavior of blends of poly(ethylene oxide) (PEO) with Carbopol were studied by thermal analysis (DSC, TGA) and infrared spectroscopy (FTIR). The miscibility of PEO/Carbopol blends in all composition ranges was confirmed, and the interaction is favored by hydrogen bonding between the carboxylic acid group of Carbopol and the PEO ether oxygen. TGA analysis showed that, with temperature increase, anhydride formation occurred first, confirmed by the FTIR bands in 1806, 1756 and 1047 cm(-1). Thermal degradation products such as carbon dioxide appear as a result of fragmentation of the anhydride ring structures and decarboxylation of the Carbopol acid groups. Bands related with unsaturated structures (1605 cm(-1)) were observed at 310 degrees C and 470 degrees C, presumably as a result of scissions of the main carbon-carbon chain. The activation energy of PEO/Carbopol blends increased with the Carbopol content in the blend, indicating that the thermal degradation is delayed with the presence of Carbopol. (C) 2000 Elsevier Science Ltd. All rights reserved.