The miscibility of poly (4-vinylpyridine) (P4VP) with poly (4-vinylphenol) (PVPh) blends was investigated over a wide range of compositions by differential scanning calorimeter (DSC), Fourier transform infrared spectroscopy (FTIR), and high-resolution solid-state nuclear magnetic resonance (NMR) spectroscopy. DSC results show that the T(g)s of the P4VP/PVPh blends are much higher than those of the calculated weight-average values. The proton spin-lattice relaxation times in the laboratory frame, T-1(H), and the rotating frame, T-1p (H), were studied as a function of blend composition. T1(H) and T-1p(H) results demonstrate that the spin diffusion can completely average out the entire relaxation process. It was also found that the intimate mixing of the polymer blends restricts the local chain mobility. (C) 2001 Elsevier Science Ltd. All rights reserved.