Carbon nanotubes (CNTs) were dispersed in poly (tetramethylene ether glycol), (PTMEG) at a concentration of 0.1 wt% by ultrasonication in the pulse mode at 50-55 °C. Altering the sonication time resulted in different states of carbon nanotubes dispersion. Control samples of PTMEG sonicated for different times were also prepared. Results of linear viscoelastic measurements and ultraviolet –visible (UV-Vis) spectroscopy analysis revealed an improvement in the CNT dispersion state with sonication time. Moreover, the sedimentation behavior for these samples pointed out to the formation of CNT networks with different microstructures for different sonication times. TGA results showed an increase in thermal stability of the suspensions with increasing sonication time followed by a decrease at long sonication times. TGA data and rheological properties for the control PTMEG samples showed no degradation with increased sonication time. These results seem to indicate that potential CNT breakage and changes in the CNT network microstructure may explain the decrease in the suspension thermal stability at long sonication times. Optimization of the ultrasonication parameters in order to avoid CNT damage while achieving good dispersion is essential.