The thermal stability and degradation of poly(vinyl alcohol) (PVA), PVA + H3PO4 (solid polymer electrolyte, SPE), PVA containing methylene blue (MB) dye and SPE (PVA + H3PO4) + MB were studied by TG/DTA/DTG and DSC techniques. The FTIR and UV-vis study of these materials indicates that MB forms a complex with the polymer by a hydrogen bonding interaction between the -OH group of the polymer and the nitrogen of MB and improves the thermal stability of the polymer. © 2002 Elsevier Science Ltd. All rights reserved.