Temperature-sensitive polyurethanes are obtained by reacting trifunctional isocyanate with poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) [Pluronic L122]. The temperature-dependent interactions among poly(propylene oxide) [PPO] segments are observed by n.m.r. At low polyurethane concentrations, segment-segment PPO interactions within a given gel cluster are predominant, whereas above the concentration threshold, interparticle interactions lead to the aggregation of clusters. The formation of physical networks in polyurethane suspensions with the temperature increase is followed by the appearance of temperature- and shear-thinning viscoelastic gels.