The end-capped telechelic HEUR associative polymer was reported to exhibit a single mode Maxwell typed relaxation behavior. Annable et al. (1993) suggested that the single mode Maxwell relaxation time corresponded to the lifetime of the hydrophobe in the micellar junction. However, results from some recent publications suggested that a more complex relaxation behavior existed. In order to verify this, a hydrophobically modified urethane-ethoxylate (HEUR) polymer with M-n of 26 000 and a C20H41 hydrophobe was synthesized for the present study. Results from oscillatory measurements of a 2 wt % sample in distilled water indicates that two different relaxation modes are present. This is confirmed with a two-mode Maxwell model and the determination of the relaxation time spectrum from the dynamic moduli data. Further analysis of the data at different temperatures confirmed that one of the modes is possibly related to the lifetime ( similar to 0.01 s at 25 degrees C) of the hydrophobe in the micellar junction and the other to the network relaxation ( similar to 6 a at 25 degrees C). The lifetime is in the same order of magnitude as determined by NMR for other associative polymer systems (Petit-Agnely and Iliopoulos, 1999). This is the first experimental verification that the lifetime and network relaxation time can be differentiated in a model HEUR polymer system. (C) 2000 The Society of Rheology. [S0148-6055(00)00801-4].