Thermotropic polymers consisting of mesogenic units in the main chain have attacted attention for the demand of high performance materials. We reported tha polyurethanes obtained by polyaddition of 1,4-phenylene diisocyanate or 2,5-tolyene dissocyanate, with 1,4-bis(ω - hydroxyalkoxy)benzene showed montropic liquid crystalline behaviors. In the present study, thermotropic prepertices 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.