Segmented Polyurethane Elastomers with Liquid Crystalline Hard Segments. 3. Infrared Spectroscopic Study

Segmented liquid crystalline polyurethanes (LCPUE) have been studied by infraredspectroscopy. The nematic liquid crystalline hard domains act as physical cross-links and can be orientedby the application of mechanical strain. The orientation function achievable in the hard segments resultsfrom the combination of mechanical strain and stress-softening. Furthermore, elastic deformation inducesthe rearrangement of some hard segments in the mesophase into a more ordered packing. Hightemperatureinfrared spectra have been correlated with thermal transitions of the LCPUE, and a liquidliquidmicrophase-separated morphology above the isotropization of the mesophase appears to exist.