EXAMINATION OF MISCIBILITY AT MOLECULAR-LEVEL OF POLY(HYDROXYETHER OFBISPHENOL-A) POLY(N-VINYL PYRROLIDONE) BLENDS BY CROSS-POLARIZATION MAGIC-ANGLE-SPINNING C-13 NUCLEAR-MAGNETIC-RESONANCE SPECTROSCOPY

The miscibility of poly(hydroxyether of bisphenol A) (phenoxy) and pol y(N-vinyl pyrrolidone) (PVP) was investigated by differential scanning calorimetry (DSC) and high-resolution solid-state nuclear magnetic re sonance (NMR) techniques. The DSC studies showed that the phenoxy/PVP blends have a single, composition-dependent glass transition temperatu re (T-g). The S-shaped. T-g-composition curve of the phenoxy/PVP blend s was reported, which is indicative of the strong intermolecular hydro gen-bonding interactions. To examine the :miscibility of the system at molecular level, high-resolution solid-state C-13 nuclear magnetic re sonance (NMR) technique was employed. Upon adding phenoxy to system, t he chemical shift of carbonyl carbon resonance of PVP was observed to shift downfield by 1.6 ppm in the C-13 cross-polarization (CP)/magic a ngle spinning (MAS) together with the high-power dipolar decoupling (D D) spectra when the concentration of phenoxy is 90 wt %. The observati on was responsible for the formation of intermolecular hydrogen bondin g. The proton spin lattice relaxation time T-1(H) and the proton spin- lattice relaxation time in the rotating frame T-1 rho(H) were measured as a, function of the blend composition. The T-1(H) result was in goo d agreement with the thermal analysis, i.e., the blends are completely homogeneous on the scale of 20 similar to 30 nm. The six results of T -1 rho(H) further indicated that the blends were homogeneous on the sc ale of 40 similar to 50 Angstrom. (C) 1998 John Wiley & Sons, Inc.