6533b839fe1ef96bd12a5954

RESEARCH PRODUCT

Micellization and Micellar Structure of a Poly(ethylene oxide)/Poly(propylene oxide)/Poly(ethylene oxide) Triblock Copolymer in Water Solution, As Studied by the Spin Probe Technique

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The micellization of the triblock copolymer Pluronic P85 (poly(oxyethylene)27/poly(oxypropylene)39/poly(oxyethylene)27) in aqueous solution was followed vs temperature and addition of aliphatic alcohols, using the spin probe technique. Different types of probes properly chosen (spin-labeled (SL) poly(oxyethylene(4))nonylphenol, SL-Pluronic L62, TEMPO-laurate, TEMPO-hexanoate, CAT 4, CAT 8, CAT 11, CAT 16, and 5-, 7-, 10-, and 12-doxylstearic acids) provided information about the micellar structure (polarity, viscosity, and order degree) at different radial locations. Micellization was found to be low at room temperature, even for 10% aqueous solutions, but strongly increasing with temperature increase to about 323 K. Hydration of the poly(oxyethylene) (PEO) chains in the shell was found to diminish toward the interior and with increasing temperature. At an intermediate region of the shell, a hydration number ([H2O]/EO unit) close to 3 was found at 293 K, which decreased to ∼1 at 323 K. No hydration was fo...