Structural changes and segmental orientation behavior of polyurethane have been studied during uniaxial deformation. The orientation function change of the two (free and hydrogen bonded C=O stretching peaks) peaks during a full cycle of deformation has been observed to be distinctively different. Even though the hydrogen-bonded C=O peaks showed hysteresis behavior, the free C=O peaks exhibited quite elastic behavior. It was thus concluded that the orientation behavior of free and hydrogen-bonded C=O stretching peak represents the deformation characteristics of soft and hard domains, respectively. The orientation behavior at different temperatures also has been studied. Temperature has a significant effect on the orientation behavior of the soft domain, whereas it has negligible effect on the hard domain orientation. It was also demonstrated that the structural change due to the deformation could be analyzed by infrared spectroscopy. Some of the hydrogen-bonded carbonyl groups have been observed to be transferred to the free carbonyl groups, indicating that a small amount of the hard segments in the hard domain have been pulled out into the soft matrix upon deformation. The orientational relaxation also has been studied as a function of time. The segmental relaxation of the hard segments appears to be quite characteristic depending on the nature of the domain in which they reside. (c) 1994 John Wiley & Sons, Inc.