Bioblends of the biodegradable copolyester poly(tetramethyleneadipate-co-terephthalate) (EBU) and polystyrene (PS) were prepared in different weight compositions on a twin-screw extruder at 160-200 degrees C. The various bioblend compositions were then investigated using thermogravimetric analysis (TGA), modulated differential scanning calorimetry (MDSC), and Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS). TGA studies showed that 25/75 and 50/50 EBU/PS blends had higher thermal stability than the more thermally stable blend component, PS. The MDSC studies showed a single T. and single T for the blends, that were concentration independent. The FTIR-PAS studies indicated a small shift (4-8 cm(-1)) in the carbonyl absorption peaks of EBU to lower wavenumbers in 50/50 EBU/PS blend relative to that of neat EBU. It is concluded that, while the MDSC results were inconclusive, the TGA and FTIR-PAS results support the existence of some degree of intermolecular interaction between EBU and PS components and, hence, partial compatibility in EBU/PS blends. (C) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 110: 2932-2941, 2008