Poly(p-vinylphenol) (PVPh) and poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) formed interpolymer complexes in methanol, ethanol, or methyl ethyl ketone. However, only polymer blends were obtained from tetrahydrofuran or dimethylformamide. Each of the complexes and blends showed one composition-dependent glass transition temperature (T-g), indicating its single-phase nature. Positive deviations of T-g values were observed for both complexes and blends, suggesting a strong interaction between the two components. Thermal treatment at 190 degrees C resulted in an increase in T-g for the blends as well as the complexes. Fourier transform infrared spectroscopy revealed the existence of hydrogen-bonding interactions between the hydroxyl groups of PVPh and the carbonyl groups of PDMAEMA in the blends and complexes. In addition, X-ray photoelectron spectroscopy showed that the nitrogen atoms in PDMAEMA are also involved in hydrogen-bonding interactions as shown by the development of a high-binding-energy N1s peak in each complex or blend. Ab initio calculations on dimers of the saturated monomers revealed that the carbonyl oxygen and the nitrogen are about equally favored as proton-accepting sites.