Blends of poly(2,6-dibromo-1,4-phenylene oxide) (PDBrPO) with 4.8 mol % sulfonated polystyrene (4.8SPS), Na-neutralized 1.7 mol % sulfonated polystyrene (Na1.7SPS), Mn-neutralized 3.8 mol % sulfonated polystyrene (Mn3.8SPS), and Zn-neutralized 3.8 mol % sulfonated polystyrene (Zn3.8SPS) ionomers were investigated for their miscibilities with varying compositions by dilute solution viscometry (DSV), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). Deltab, mu, and alpha parameters by W. R. Krigbaum and F. J. Wall (J Polym Sci 1950, 5, 505), K. K. Chee (Eur Polym J 1990, 4, 423), and Z. Sun et al. (Eur Polyrn J 1992, 28, 1259), respectively, were calculated from DSV data to determine miscibility. Na1.7SPS is immiscible with PDBrPO in no relation to the blend compositions. On the other hand, the increasing extent of miscibility of the blends reflected by the data is as follows: 4.8SPS < Mn3.8SPS < Zn3.8SPS. DSC and SEM results are also in agreement with the DSV data except for the alpha parameter, which showed some disagreements with Deltab and mu parameters in a few blends. (C) 2001 John Wiley & Sons, Inc.