Thermoplastic polysulfone (PSF) was melt blended with a novel oligomer poly(bisphenol-A) (m-BPA) to produce samples of varying composition by weight PSF/m-BPA of 99/1, 95/5, 90/10, and 58/42.. Miscibility studies, performed via differential scanning calorimetry and dynamic mechanical spectroscopy, show a single T-g, intermediate to the pure component T(g)s, over the composition range of 1-42 wt% oligomer. Viscosity, tensile properties, moisture uptake, aging rate, specific volume, PALS free volume, and thermal stability of the blends are examined. Addition of as little as 1 wt% m-BPA to PSF reduces melt viscosity as measured by rheometry and causes a significant reduction in torque and RPM in the Brabender Plasti-corder. Addition of m-BPA to PSF causes a ductile to brittle transition in tensile properties, a decrease in relative free volume as probed by positron annihilation lifetime spectroscopy (PALS) and a decrease in water diffusion coefficient. Aging results in a decrease in the relative concentration of free volume elements for high tn-BPA loadings. Humidity absorption produces a decrease in the relative size of free volume elements in the pure components and the blends. The thermal stability of the blends with low loadings of m-BPA (480-504 degrees C) is comparable to that of PSF (499-504 degrees C). The aging rate of the blends is intermediate to that of the pure components.