FTIR analysis of hydrogen bonding in amorphous linear aromatic polyurethanes. II. Influence of styrene solvent

Fourier‐transform infrared (FTIR) spectral studies were carried out on a polyurethane in styrene solutions at styrene concentrations from 30 to 90% (w/w). NH vibrations were studied in the stretching and bending regions. The results demonstrated that the NH groups of the polyurethane can hydrogen bond not only with the CO groups but also with other groups in this system. The investigation of the vibrations of the monosubstituted aromatic rings confirms that some aromatic rings of the styrene are hydrogen bonded with the NH groups of the polyurethane. With the results of Part 1 of this series, the mole fractions of “free” NH groups and of NH groups H‐bonded to CO groups and to the π orbitals of the aromatic rings were obtained. These results are useful in elucidating why a physical gel appears in this system. © 1994 John Wiley & Sons, Inc.