Thermotropic polymers consisting of mesogenic units in the main chain have attracted attention for the demand of high performance materials. We reported that polyurethanes obtained by polyaddition of 1,4-phenylene diisocyanate or 2,5-tolylene diisocyanate, with 1,4-bis(w-hydroxyalkoxy)benzene showed monotropic liquid crystalline behaviors. In the present study, thermotropic properties of liquid crystalline polyurethanes have been investigigated by wide-angle x-ray scattering and infrared spectroscopy. Curve-fitting analysis of the C=O band region of infrared spectra at various temperatures revealed three bands the ordered H-bonded carbonyl band the disordered H-bonded carbonyl band, and the free carbonyl band. The mesomorphic behavior of the polyurethanes was greatly dependent on the hydrogen bonds between the urethane linkage.