The miscibility of blends of poly(alpha-methyl styrene-co-methacrylic acid) (P alpha MSMA) with Various alkyl methacrylate polymers or poly(alkyl methacrylate-co-4-vinylpyridine) was studied by differential scanning calorimetry and Fourier transform infra red spectroscopy. P alpha MSMA is immiscible with poly(methyl methacrylate), poly(ethyl methacrylate) and poly(n-butyl methacrylate). The introduction of 4-vinylpyridine by random free radical copolymerization within these alkyl methacrylate polymer chains enhanced the miscibility of these copolymers with P alpha MSMA as a result of specific interactions that occurred between the carboxylic and pyridine groups, evidenced from the significant changes observed by FTIR in the carboxyl and pyridine ring regions. The density of interacting groups required for miscible blends depends on the size of the pendant group.