A series of side-chain type liquid crystalline polyurethanes have been synthesized from the mesogenic diol monomer with hexamethylene-, p-phenylene-, or bitolylene-diisocyanate. The mesomorphic properties has been investigated by differential scanning calorimeter DSC), wide angle X-ray scattering (WAXS), polarized light microscopy, and Fourier transfer infrared (FT-IR) spectroscopy. The polyurethanes exhibit an enantiotropic mesophase with nematic or smectic depending upon the flexibility of urethane bond in the polymer backbone. Thermal properties are deeply influenced by the hydrogen bonding among the polymer backbone.