This contribution presents a study of the hydrogen-bonding interactions between poly(styrene-comethacrylic acid) containing 22 mol% methacrylic acid (SMA-22) and poly(ethyl methacrylate) (PEMA), poly[2-(N,N-dimethylamino) ethyl methacrylate] (MAD), or polylstyreneco-[2-(N,N-dimethylamino) ethyl methacrylate]} containing 3, 12, or 21 mol% 2-(N,N-dimethylamino) ethyl methacrylate (SMAD-3, SMAD-12, or SMAD-21) by viscometry and differential scanning calorimetry (DSC). On the basis of the analysis of DSC thermograms and viscometric measurements, polymer miscibility was observed with the PEMA/SMA-22 system. This miscibility was due to hydrogen-bonding specific interactions between carbonyl groups of PEMA and carboxylic groups of SMA-22. The SMAD-3/SMA-22 system was immiscible, whereas complexation was observed with PMAD/SMA-22, SMAD-21/SMA-22, and SMAD-12/SMA-22 mixtures in butan-2-one. This complexation was due to stronger interactions between poly(styrene-co-methacrylic acid) and the 2-(N,N-dimethylamino) ethyl methacrylate groups of PMAD or SMAD copolymers, as evidenced by viscometry and DSC. A similar phenomenon was observed for PMAD/SMA-22 and SMAD-21/SMA-22 mixtures in tetrahydrofuran. For the SMAD-12/SMA-22 system in this solvent, such behavior was noted only in the presence of an excess of the copolymer SMAD-12. This study showed that the minimum amount of interacting species required for the interpolymer complexation was higher in tetrahydrofuran than in butan-2-one. (c) 2005 Wiley Periodicals, Inc.