HIGH-RESOLUTION SOLID-STATE C-13 NUCLEAR-MAGNETIC-RESONANCE STUDY ON POLY(VINYL ALCOHOL) POLY(VINYLPYRROLIDONE) BLENDS

The miscibility and domain structure of poly(vinyl alcohol)/poly(vinylpyrrolidone) (PVA/PVP) blends are investigated by high-resolution solid-state C-13 nuclear magnetic resonance methods. The observed C-13 spectra and the intermolecular cross-polarization of the blends suggest a hydrogen-bonding interaction between the two polymers. H-1 T1 and T1-rho results indicate that the blends are miscible at all compositions on a scale of 200-300 angstrom. On a scale of 20-30 angstrom, however, the miscibility of the blends depends significantly on the composition. When the PVA composition is more than 46 wt%, the blends are composed of two phases, an amorphous miscible phase of PVP plus PVA and a pure PVA phase. The crystallinity of the PVA phase decreases rapidly with decreasing PVA composition. When the PVA composition is less than 46 wt%, the blend is completely miscible. The composition of PVA phase in the blends was inferred from the results of H-1 T1-rho.