Abstract
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, C 10OS, decyltrimethyl ammonium bromide, C 10TAB, and pentaethylene glycol monodecyl ether, C 10E 5, 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 C 10OS than with cationic and non-ionic ones. The presence of the two Pluronics induces the same lowering of the aggregation number of C 10OS as shown by fluorescence quenching measurements. The number of polymer chains necessary to bind each C 10OS aggregate has been estimated to be ∼6 for PE6200 and ∼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.
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