In aqueous solutions of the triblock copolymer F88 (EO96PO39EO96) micelle formation has been studied by means of dual fluorescence of the probe molecule 1,3-bis(1-pyrene)propane monitoring viscosity changes in its microenvironment. Mobility changes of the polymer molecules on micellization were followed by means of pulsed field gradient (PFG) NMR. These results complement a recent detailed study of cis−trans isomerization of azo dyes as “kinetic probes” for structure formation in aqueous solutions of F88 (Langmuir 2001, 17, 2907). Differences of the critical micellization temperatures determined by various methods, and in H2O and D2O as solvents, are discussed. Our results reflect the particular large content of polye(ethylene oxide) in F88 (80%) compared to other triblock copolymers of this type.

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