Miscibility and specific interactions in blends of poly(n-vinyl-2-pyrrolidone) and acid functional polyester resins.

Miscibility and intermol. interactions of novel blends of poly(N-vinyl-2-pyrrolidone) (PVP) and acid functional polyester resins (APE) were studied by use of Differential Scanning Calorimetry (DSC), Attenuated Total Reflectance Fourier Transform IR (ATR-FTIR), Cross-Polarization Magic Angle Spinning (CPMAS) 13C NMR spectroscopy and 1H NMR relaxometry. The miscibility is found to be correlated to the no. of acid end groups (acid value, AV) of APE and the molar mass (M) of PVP. Blends of APE with high AV and PVP with high M exhibit single-phase behavior in DSC and 1H NMR. Both ATR-FTIR and 13C NMR of these blends show compn.-dependent displacements of the APE and PVP signals, which confirms that the two polymers are close together in the blend. In particular, FTIR spectra reveal a systematic blue shift of the stretch vibrations of both PVP and APE carbonyl groups. This indicates dipole-dipole interactions between a carbonyl group of PVP and a carbonyl of APE. The spectra contain a broad peak at about 1630 cm-1, which appears as a shoulder of the carbonyl stretch vibration of PVP. This band is ascribed to hydrogen bonding between the carbonyls of PVP and the hydrogen atoms of the end groups of the APE resins. Anal. of temp.-varied FTIR spectra of blends of PVP and a polyester resin of neopentyl glycol and isophthalic acid (PNI), used as a model of the APE resin, confirms the existence of such interactions