Summary: Differential scanning calorimetry (DSC) and inverse gas chromatography (IGC) were used to determine the physicochemical properties of blends of poly(4-vinylphenol-co-methyl methacrylate) (PVPhMMA50) containing 50% of methyl methacrylate with poly(styrene-co-4-vinylpyridine) (PS4VPy 30) containing 30 mol% of 4-vinylpyridine. Specific retention volumes (Vg) and Flory-Huggins interaction parameter () for eight probes with different polarities were calculated at the 180–200 °C temperature range using PVPhMMA50, PS4VPy30 and their blends as stationary phases. Moreover, some thermodynamic properties of PVPhMMA50 and PS4VPy30 such as the weight fraction coefficient activity and the solubility parameters of both components (δ2) were also calculated at infinite dilution. Both the obtained specific retention volume values with the different polymer blends and the calculated polymer-polymer interaction parameters () allowed us to conclude that the binary blends of two polymers are miscible in all proportion. These results are in good agreement with the phase behaviour observed by DSC.