The interaction in aqueous solution between either the normal block copolymer poly(ethylene oxide)-poly(propylene oxide)-poly (ethylene oxide): Pluronic PE6200 [(EO)(11)-(PO)(28)-(EO)(11)], or the reverse block copolymer poly(propylene oxide)-poly (ethylene oxide)-poly(propylene oxide): Pluronic 25R4 [(PO)(19)-(EO)(33)-(PO)(19)] and the surfactants sodium decylsulfate, C10OS, decyltrimethyl ammonium bromide, C(10)TAB, and pentaethylene glycol monodecyl ether, C10E5, was investigated and the aggregation behavior of these surfactants with Pluronics was compared. Surface tension measurements show that Pluronics in their non-aggregated state better interact with the anionic surfactant C10OS than with cationic and non-ionic ones. The presence of the two Pluronics induces the same lowering of the aggregation number of C10OS as shown by fluorescence quenching measurements. The number of polymer chains necessary to bind each C10OS aggregate has been estimated to be similar to 6 for PE6200 and similar to 2 for 25R4. Furthermore, this surfactant also induces the same increment in the gyration radius of the polymers as revealed by viscosimetry. Calorimetric results have been reasonably reproduced by applying a simple equilibrium model to the aggregation processes. (c) 2006 Published by Elsevier Inc.