Solubilization of pyrene and steroid hormones into aqueous solutions of an associative polymer, poly-(ethylene oxide)-b-poly(propylene oxide)-b-(poly(ethylene oxide))-g-poly(acrylic acid) (Pluronic-PAA), has been studied. A dramatic increase of solubilization is observed upon formation of micelles above the critical micellization temperature (cmt). The equilibrium partition coefficients of the probes between micelles and water (Km/w) above the cmt strongly correlate with the probe's octanol/water partition coefficient (Ko/w). The Km/w is increased with the ionization degree of the poly(acrylic acid) (PAA) segments. Preferential solubilization of the increasingly hydrophobic compounds into the Pluronic-PAA is dominated by the entropic effect. Comparison of the fraction of the probe located in the hydrophobic cores of the micellar aggregates for pyrene and estradiol illustrates the degree of chemical specificity of the Pluronic-PAA micellar aggregates, which is due to the hydrophobicity of the probe.

A novel class of self-assembling amphiphilic polymers is introduced whereby a Pluronic poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymer is end-modified by poly(vinyl alcohol) (PVA). The copolymer is temperature-sensitive in aqueous solutions due to the temperature-dependent water solubility of PPO. The Pluronic-PVA copolymers show a dramatic temperature dependency of their aggregation. The attachment of PVA segments to the Pluronic molecule increases its critical aggregation temperature. At concentrations of 10% and higher and temperatures above 10-20 °C, the Pluronic-PVA aqueous solutions yield gels. The gelation and formation of large aggregates coincide, indicating that the gelation is caused by the formation of aggregates with interpenetrating coronas. A decline in the power law relaxation exponent of the light scattering is observed upon gelation, which is due to the nonergodicity of the gels.