Miscibility of poly(methacrylic acid)/poly(4-vinylpyridine) blends and complexes investigated by high-resolution solid-state 13C NMR

Polymer blends and complexes prepared from poly(methacrylic acid) (PMAA) and poly(4-vinylpyridine) (P4VPy) were investigated by differential scanning calorimetry (DSC) and high-resolution solid-state 13C nuclear magnetic resonance (NMR) spectroscopy. Complexes were obtained from ethanol/water (1:1) solutions, whereas blends were cast from dimethylformamide (DMF) solutions. Each of the complexes and blends showed one composition-dependent glass transition temperature (Tg), indicating that both the complexes and the blends are homogeneous on a scale of 10–30 nm. Furthermore, the Tg value of a complex is much higher than that of a blend with the same composition. Measurements of the proton spin–lattice relaxation time in the rotating frame, T1ρ(H), reveal that each of the complexes and blends has one composition-dependent T1ρ(H), indicating that both the complexes and the blends are homogeneous on a scale of 1–3 nm. However, the calculated domain sizes of the complexes and blends are almost the same.