Infrared and x-ray diffraction studies of a semirigid polyurethane

Morphology of polyurethanes with triol monomer crosslinked on hard segments

“…It is well known that the infrared absorbance of H-bonded urethane carbonyl appears at lower wave numbers than that of free urethane carbonyl. 26,39,40 The amide-I infrared spectra of semicrystalline samples such as nylons 41 and polyurethanes 42 have been reported to comprise distinct spectral features due to the degree of the carbonyl H-bonding: namely, H-bonded carbonyl groups in ordered ("crystalline") domains (1697-1706 cm Ϫ1 ), Hbonded carbonyl groups in disordered ("amorphous") conformations (1714 -1718 cm Ϫ1 ), and non-H-bonded (free) carbonyl groups (1731-1734 cm Ϫ1 ). Similarly, two distinct bands were observed in the N-H stretching region, i.e., 3322-3329 and 3441-3450 cm…”

Preparation and Properties of Polyurethanes Containing Mesogenic Units

“…Figure 5 shows the frequency shift in IR spectra of 3a, 3d, and 3e as a function of temperature in the range of 20 to 250°C, including the N-H stretch and the C = 0 stretch of which frequencies and relative intensities are characteristic of hydrogen bond formation. 9 It was found that the stretches regarded as hydrogen bonding C = 0 as well as N-H vibration of polyurethanes gradually shift to higher frequency region with increasing temperature around their melting points. These facts suggest that the hydrogen bonding plays an important role in the development of mesophases in 3.…”

“…These facts suggest that the hydrogen bonding plays an important role in the development of mesophases in 3. 9 All of 3 having structure corresponding to 1 showed a smectic phase since the mesogenic groups in the main chains are restricted to align by intermolecular interaction.…”

Preparation and properties of waterborne polyurethane–urea anionomers. I. The influence of the degree of neutralization and counterion

“…Some researchers have reported that the band centered around 1725 cm Ϫ1 is attributable to the stretching of urethane carbonyl groups, whereas the urethane carbonyl stretching around 1710 cm Ϫ1 is due to hydrogen bonding in disordered regions. 17,18 This urethane carbonyl stretching around 1710 cm Ϫ1 is attributable to the carbonyl participating in the urethane linkage of interfacial regions or being dissolved in the soft phase. The stretching of the stronger hydrogen bonds in ordered or crystalline regions occurs at a lower frequency around 1695 cm…”