Light-Scattering Studies of a Block Poly(oxyethylene-oxypropylene-oxyethylene) Copolymer in Water/o-Xylene Mixtures

Wu, Guangwei; Chu, Benjamin

doi:10.1021/ma00085a015

Cited by 57 publications

(61 citation statements)

References 18 publications

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“…The hydration gradient in the core was determined for the L62 reverse micelles, the range of W eff values being much larger in the presence of the nonpolar solvent. 5. The values of the polarity-sensitive parameters of most probes in the reverse micelles have also been "translated" into values of KosowerÅs Z polarity factor.…”

Section: Discussionmentioning

confidence: 99%

Micropolarity and Order in the Reverse Micelles of L62 and L64 Pluronic Copolymers, As Studied by Molecular Probe Techniques

et al. 1998

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The reverse micelles of triblock copolymers poly(ethylene oxide)-block-poly(propylene oxide)-block-poly-(ethylene oxide) EO 6 PO 36 EO 6 (Pluronic L62) and EO 13 PO 30 EO 13 (Pluronic L64) in ternary (copolymer/oxylene/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 polarity by comparison with a series of poly(oxyethylene)/water (TEG/water) calibration mixtures. The data were concordant and complementary, resulting in polarity profiles of the core for all systems and the relative radial positioning of the probes. The order of decreasing hydrophobic character found was Dansyl > NP > CAT 16 > CAT 11 ∼ ANS > CAT 8 > PSA > CAT 4 > CAT 1. A linear relationship was found between the R A (the intensity ratio of two absorption vibronic bands) of PSA in ethanol/water mixtures and Kosower's Z parameter (Z ) -29.0R A + 177.83). Thus, by means of the calibration mixtures, converting different spectral parameters of the mentioned probes, the local polarity values were expressed in terms of Z values. The role of water as a prerequisite for micellization was evidenced and so was the minimum quantity of water required in the ternary systems (W ) 0.2 for L64 and W ) 0.4 for L62). Regarding the water distribution, a more advanced segregation of water is observed in the ternary systems as compared to the binary ones, pointing to the role played by the solvent in this process. Evidence was found for a considerable solvation of the poly(propylene oxide) block with xylene, leading to a looser packing in the corona and in the poly(ethylene oxide) core. In the case of ternary systems, the ordering of the polymer chains in the micelles, measured with a series of x-doxylstearic acid spin probes, indicates the progress of micellar organization with increasing water content, the order increasing and extending further from the polar core and the corona becoming less penetrable. In the corresponding binary systems, the polymer chain rotation is "frozen" at room temperature (295 K) and even at 320 K. The structural characteristics of L62 and L64 ternary systems are rather similar, a conclusion suggested especially by the information the polar probes supplied. There are differences in the microenvironment of more hydrophobic probes, which sense a higher hydrophobicity in the case of L62, the increase of microviscosity being also more marked in the L62 system.

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Section: Discussionmentioning

confidence: 99%

Micropolarity and Order in the Reverse Micelles of L62 and L64 Pluronic Copolymers, As Studied by Molecular Probe Techniques

et al. 1998

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“…However, the more hydrophilic PEO, remains water soluble even up to the boiling point of water, though its LCST can be brought down by the addition of salts [28][29][30][31][32][33][34][35]. It is worth noting that these solutions are often used in the presence of additives [28][29][30][31][32][33][36][37][38][39] in order to acquire desirable properties for different applications. On the basis of literature data, it is clear that the addition of salt in aqueous solutions of EO-PO copolymers can have two effects that depend on the chemical nature of the salt and/or its concentration.…”

Section: Clouding Behavior Of T904mentioning

confidence: 99%

Induced micellization and micellar transitions in aqueous solutions of non-linear block copolymer Tetronic® T904

Kadam

Singh²,

Marangoni³

et al. 2010

Journal of Colloid and Interface Science

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“…The hydrodynamic radius (R h ) is calculated from the DLS data by the Stokes-Einstein equation, assuming that the aggregates are of sphere shape. [23] The average hydrodynamic radii measured by DLS are shown in Table 1. The particle diameters measured by TEM are a little smaller than hydrodynamic diameters measured by DLS.…”

Section: Formation Of the Vesiclesmentioning

confidence: 99%

Self‐Assembly of a Hydrophobic Polypeptide Containing a Short Hydrophilic Middle Segment: Vesicles to Large Compound Micelles

Sun

Shi

Chen

et al. 2008

Macro Chemistry & Physics

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This report describes a facile route to prepare the vesicles and large compound micelles (LCMs) from a series of poly(ε‐benzyloxycarbonyl L‐lysine)‐block‐poly[diethylene glycol bis(3‐amino propyl) ether]‐block‐poly(ε‐benzyloxycarbonyl L‐lysine) (PZLL‐DGBE‐PZLL) in their water solution, depending on molecular weight of the polypeptides. A pyrene probe is used to demonstrate the aggregate formation of PZLL‐DGBE‐PZLL in solution, and also to measure their critical micelle concentration as a function of molecular weight of the polymer. Transmission electron microscopy, atomic force microscopy, dynamic light scattering and confocal laser scanning microscopy are used to observe their aggregate morphologies. Rhodamine B is used as a fluorescent probe to confirm the structure of large compound micelles composed of many reverse micelles with aqueous cores. These polypeptides are prepared by ring‐opening polymerization of α‐amino acid N‐carboxyanhydrides with a small molecule as the initiator. Their structures are confirmed by NMR and SEC‐MALLS. These vesicles and large compound micelles are extremely expected to be used in drug delivery.magnified image

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Light-Scattering Studies of a Block Poly(oxyethylene-oxypropylene-oxyethylene) Copolymer in Water/o-Xylene Mixtures

Cited by 57 publications

References 18 publications

Micropolarity and Order in the Reverse Micelles of L62 and L64 Pluronic Copolymers, As Studied by Molecular Probe Techniques

Micropolarity and Order in the Reverse Micelles of L62 and L64 Pluronic Copolymers, As Studied by Molecular Probe Techniques

Induced micellization and micellar transitions in aqueous solutions of non-linear block copolymer Tetronic® T904

Self‐Assembly of a Hydrophobic Polypeptide Containing a Short Hydrophilic Middle Segment: Vesicles to Large Compound Micelles

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