Infrared studies on segmented polyurethane-urea elastomers

Structural studies on hydrogen bonding in segmented polyurethane-urea elastomers were made using IR spectroscopy. Further, the orientation behavior of both the hard and soft segments on deformation was investigated using IR dichroism measurements. Hydrogen bonding was found to be formed not only between the hard segments but also between the soft segments, through urea and urethane groups, respectively. Changes in the extent of hydrogen bonding on deformation were related to segmental orientation behavior, and mechanical properties such as stress-strain and stress hysteresis. The hard segments orient preferably transverse to the stretch direction to high elongations, and show hysteresis of orientation on cyclic straining. The orientation behavior of the soft segments is approximately reversible on repeated deformation. In the range of comparatively small elongation, however, the deformation of the soft segments is larger than the external deformation. From these experimental facts, the mechanism of the rubber elasticity of segmented polyurethane-urea elastomers is qualitatively explained.