Imidazole derivatives as absorption probes for pluronics core-shell aggregates micropolarity investigation

Abstract

Using the absorption probes 1-H-imidazol-1-yloxy-4,5-dihydro-4,4,5,5-tetramethyl-2-ethyl-3-oxide, 1-H-imidazol-1-yloxy-4,5-dihydro-4,4,5,5-tetramethyl-2-nitrophenyl-3-oxide, and 1-H-imidazol-1-yloxy-4,5-dihydro-4,4,5,5-tetramethyl-2-undecyl-3-oxide, the micropolarity of micellar aggregates formed in aqueous solutions of poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) triblock copolymers, Pluronics L62, L64, and F127, as well as in reverse micellar systems of F127/butanol/water, has been investigated These absorption probes have different hydrophilic/hydrophobic features and solvatochromic properties. Their specific absorption parameters, sensitive to changes in micropolarity, were calibrated using the reference curves carried out in homogeneous tetraethyleneglycol/water mixtures. The probes were able to detect changes in the micelle micropolarity induced by hydration. Thus, with the help of calibration solutions, the effective local hydration of the polymeric chain sensed by the molecular probe solubilized in the guest aggregate was quantified and hypothetical relative locations of the probes in micelles have been proposed. The probes evidence differences in the micropolarity function of the structure (nature) and concentration of the Pluronic block copolymers.