The miscibility behavior of poly(2-ethyl-2-oxazoline) (PEOx)/poly(vinyl phenyl ketone hydrogenated) (PVPhKH) blends was studied for the entire range of compositions. Differential scanning calorimetry and thermomechanical analysis measurements showed that all the PEOx/PVPhKH blends studied had a single glass-transition temperature (T-g). The natural tendency of PVPhKH to self-associate through hydrogen bonding was modified by the presence of PEOx. Partial IR spectra of these blends suggested that amide groups in PEOx and hydroxyl groups in PVPhKH interacted through hydrogen bonding. This physical interaction had a positive influence on the phase behavior of PEOx/PVPhKH blends. The Kwei equation for T-g as a function of the blend composition was satisfactorily used to describe the experimental data. Pure-component pressure-volume-temperature data were also reported for both PEOx and PVPhKH. (C) 2004 Wiley Periodicals, Inc.