SPECTROSCOPIC STUDIES OF PYRIDINE-CONTAINING POLYURETHANES BLENDED WITH METAL ACETATES

Natural-abundance N-15 nuclear magnetic resonance (NMR) experiments sh ow direct evidence for metal-pyridine interactions in blends of pyridi ne-containing polyurethanes and metal acetates. After blending with zi nc acetate, the pyridine nitrogen peak shifts from -320 to -304 ppm; b lending with magnesium acetate causes a shift to -309 ppm. Sodium acet ate did not complex with the pyridine-containing polyurethanes; no shi fts in the C-13 NMR signal for the acetate carbonyl or in the N-15 NMR for the pyridine nitrogen are apparent. Additionally, no interactions were evident for the urethane nitrogen site in any of the blends. Pea k shifts, changes in cross-polarization dynamics, and increases in rel axation times were also apparent in the C-13 NMR spectra of the metal acetate-polymer blends. Effects of blending on the hard-domain hydroge n bonding were evident in FTIR and N-15 NMR contact-time experiments. The N-H stretching band shifted to higher wavenumbers and the N-15 NMR N-H signal persisted to longer contact times for the blend. Both spec troscopic techniques give evidence for complexation in these polyureth ane blends.