Model associative polymers based upon poly(ethylene oxide) of M-n = 8400 with a well-defined comb structure were synthesized by a condensation reaction with isophorone diisocyanate and a long-chain 1,2-diol, purified, and characterized. By H-1 NMR Re determined that one polymer, Comb-81, contains 47 mu mol of C14H29-groups per gram (ca. 2.5 groups per polymer) and Comb-83 contains 55 mu mol of C14H29-groups per gram ica. 8.8 groups per polymer). Fluorescence experiments employing pyrene as a probe show that these molecules form micelle-like aggregates in water through self-association. Aggregates of Comb-81 form at very low polymer concentrations (c(pol) < 50 ppm). Over a range of concentrations, as determined from fluorescence decay experiments, each micelle contains an average of 15 hydrophobic groups. Both dynamic light scattering and pulsed-gradient spin-echo NMR experiments indicate the hydrodynamic radii of the individual micelles formed from Comb-81 are on the order of 20-25 nm. Secondary association occurs at concentrations above ca. 0.2 wt %, and at higher concentrations leads to large increases in solution viscosity. As in other associating polymer solutions, solutions of Comb-81 exhibit a pronounced shear thinning once a critical shear rate is exceeded.