Miscibility and hydrogen bonding interaction have been investigated for the binary blends of poly(butylene adipate-co-44 mol % butylene terephthalate)[P(BAco-BT)] with 4,4'-thiodiphenol (TDP) and poly(ethylene-oxide)(PEO) with TDP; and the ternary blends of P(BA-co-BT)/PEO/TDP by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). The DSC results indicated that the binary blends of P(BA-co-BT)/TDP and PEO/TDP were miscible because each blend showed only one composition-dependent glass-transition over the entire range of the blend composition. The formation of intermolecular hydrogen bonds between the hydroxyl groups of TDP and the carbonyl groups of P(BA-co-BT), and between the hydroxyl groups of TDP and the ether groups of PEO was confirmed by the FTIR spectra. According to the glass-transition temperature measured by DSC, P(BA-co-BT) and PEO, their binary blends were immiscible over the entire range of blend composition, however, the miscibility between P(BA-co-BT) and PEO was enhanced through the TDP-mediated intermolecular hydrogen bonding interaction. It was concluded that TDP content of about 5-10% may possibily enhance miscibility between P(BA-co-BT) and PEO via a hydrogen bonding interaction. (C) 2004 Wiley Periodicals, Inc.