The miscibility of poly(hydroxyether terephthalate ester) (PHETE) with poly(4-vinyl pyridine) (P4VP) was established on the basis of thermal analysis. Differential scanning calorimetry showed that each blend displayed a single glass-transition temperature (T-g), which is intermediate between those of the pure polymers and varies with the composition of blend. The T-g-composition relationship can be well described with Kwei equation with k = 1 and q = -30.8 (K), suggesting the presence of the intermolecular specific interactions in the blend system. To investigate the intermolecular specific interactions in the blends, the model compounds such as 1,3-diphenoxy-2-propanol, 4-methyl pyridine, and ethyl benzoate were used to determine the equilibrium constants, according to Coleman and Painter model, to account for the association equilibriums of several structural moieties, using liquid Fourier transform infrared difference spectroscopy. In terms of the difference in the association equilibrium constant, it is proposed that there are the competitive specific interactions in the blends, which were confirmed by means of Fourier transform infrared spectroscopy of the blends. It is observed that upon adding P4VP to the system, the ester carbonyls of PHETE that were H-bonded with the hydroxyl groups were released because of the formation of the stronger interchain association via the hydrogen bonding between the hydroxyls of PHETE and tertiary nitrogen atoms of P4VP. (c) 2006 Wiley Periodicals, Inc.