The linear viscolastic properties of a segmented polyurethane referred to as LCPUE-1000 have been studied. LCPUE-1000 is a microphase-separated polymer with submicron mesophases as physical cross-links, and its rheological study indicates a broad transition from a viscoelastic solid to a viscoelastic liquid at the isotropization temperature of the mesophase. Furthermore, it has been found that time-temperature superposition applies in the isotropic state (160 to 110 °C). We conclude that the aggregation of liquid crystalline hard segments does enhance the connectivity of the molecular structure, and this is supported by the results of a kinetic study with dynamic mechanical spectroscopy (DMS). Physical gelation studies identify a liquid/solid transition when cooled to 106 °C or below and show the characteristic critical behavior at the gel point with a power law relaxation spectrum at low frequencies. Estimates are given for the relaxation exponent and the stiffness of the critical gel.