0000000000464850
AUTHOR
Agneta Caragheorgheopol
Polarity profiles in reverse micelles of Triton X-100, as studied by spin probe and absorption probe techniques
The microenvironment characteristics — polarity, viscosity and order degree - in Triton X-100 reverse micelles (RM) in cyclohexane and benzene — n-hexane 30 : 70 (v/v), were investigated with the aid of a homologous series of cationic spin probes, CAT n, of 5- and 16-doxyl stearic acids and of a new absorption probe, 4-nitropyridine-N-oxide (NP). The spectral parameters were related to local hydration values by means of a series of poly(oxyethylene) (PEO)/water calibration mixtures. All results regarding the polarities in RM and calibration mixtures have been expressed in terms of Kosower's Z values, by determining the linear dependence of the transition energies of NP, ENP, on Z, for a ser…
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
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 temperatu…
Micropolarity and Order in the Reverse Micelles of L62 and L64 Pluronic Copolymers, As Studied by Molecular Probe Techniques
The reverse micelles of triblock copolymers poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) EO6PO36EO6 (Pluronic L62) and EO13PO30EO13 (Pluronic L64) in ternary (copolymer/o-xylene/water) and binary (copolymer/water) systems with different water contents were evidenced and investigated by fluorescence, absorption, and spin probe techniques. The spectral parameters of the polarity sensitive probes, 1-anilinonaphthalene-8-sulfonic acid (ANS), dansylhexadecylamine (Dansyl), pyrenesulfonic acid (PSA), 4-nitropyridine N-oxide (NP) and 4-(N,N‘-dimethyl-N-alkyl)ammonium 2,2‘,6,6‘-tetramethylpiperidine-1-oxyl iodide (CAT n), were related to the local hydration and polari…