Restricted self-diffusion in an aqueous solution of poly(ethylene oxide) poly(propylene oxide) poly(ethylene oxide) triblock copolymer

Scheller, Heinrich; Fleischer, G.; Kärger, Jörg

doi:10.1007/s003960050141

Cited by 18 publications

(14 citation statements)

References 11 publications

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“…At high concentrations of the triblock copolymer F88 (25%), where all probe molecules are solubilized in micelles at temperatures above 20 °C, a clear solid gel is formed on increasing temperature. The bulk viscosity increased with a sharp breakpoint in the viscosity vs temperature curve at 31 °C. , Gel formation occurs at close packing of micelles, and an interpenetration of the PEO chains starts. Therefore, the outer part of the PEO corona of the micelles as a possible environment for the dye molecules might experience some change and accordingly also the isomerization rate.…”

Section: Resultsmentioning

confidence: 93%

Study of Structure Formation in Aqueous Solutions of Poly(ethylene oxide)−Poly(propylene oxide)−Poly(ethylene oxide) Block Copolymers by Measuring Rate Constants of the Thermal Cis−Trans Isomerization of an Azobenzene Dye and Self-Diffusion of Copolymer Molecules

et al. 1999

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In aqueous solutions of poly(ethylene oxide) (PEO)−poly(propylene oxide) (PPO)−PEO triblock copolymers (Pluronics P85, F88, and L64), structure formation (micellization) on increasing temperature was followed by determination of rate constants k iso of the thermal cis−trans isomerization of 4,4‘-nitroanilinoazobenzene by means of flash photolysis in H2O and D2O. The kinetic solvent isotope effect k iso,H 2 O/k iso,D 2 O indicates that the azobenzene dye molecules are solubilized in a water-rich environment. From the nearly constant solvatochromic UV/vis absorption band maxima λ max of the dye, it is concluded that the S shape of the ln k iso vs 1/T curves is mainly due to microviscosity changes on micellization. Critical micelle temperature values derived are in satisfactory agreement with those from self-diffusion coefficients of the copolymer molecules dependent on temperature determined by means of pulsed field gradient nuclear magnetic resonance measurements. The self-diffusion experiments allow conclusions on the size of the diffusing particles in H2O and D2O and the influence of dye molecules on aggregation. The hydrodynamic radii of the diffusing species are larger in H2O than in D2O. The reason is seen in the stronger hydrogen bonds between EO units and D2O compared to those between EO units and H2O. On gelation of 25% (w/v) F88 in water at 31° C, the bulk viscosity increases sharply but the microviscosity around the dye molecules does not.

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Section: Resultsmentioning

confidence: 93%

Study of Structure Formation in Aqueous Solutions of Poly(ethylene oxide)−Poly(propylene oxide)−Poly(ethylene oxide) Block Copolymers by Measuring Rate Constants of the Thermal Cis−Trans Isomerization of an Azobenzene Dye and Self-Diffusion of Copolymer Molecules

et al. 1999

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“…D f of the rather short chains is high, and a-the fluctuation amplitude-is small, due to the high polymer concentration of 35%. Scheller et al 7 have observed completely restricted diffusion in an aqueous gel of a pluronic copolymer, but the grain boundaries of the quasicrystalline assembly of the micelles were confirmed as diffusion barriers rather than gel-like fluctuations of network chains.…”

Section: Self-diffusion Of Styrene-methylmethacrylatementioning

confidence: 97%

“…20 The effect of boundaries between polycrystalline domains of micelles as diffusion barriers was observed by Scheller et al in aqueous gels of a Pluronics polymer. 7 The aim of this work was to investigate the formation of clusters and transient network junctions in the S-r-MMA/acetone system by measuring the self-diffusivity of the chains with PFG NMR. Physical gelation is expected to lead to anomalous diffusion.…”

Section: Introductionmentioning

confidence: 99%

Influence of associations on self-diffusion of styrene-methylmethacrylate random copolymers in semidilute acetone solution

Fleischer

Rittig

Koňák³

1998

J. Polym. Sci. B Polym. Phys.

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“…6 Their physicochemical properties have been extensively reported. [7][8][9] Light scattering, [10][11][12] fluorescence spectroscopy, [13][14][15] NMR, 16,17 specific volume, 18,19 sound absorption, 20 microcalorimetry, 21,22 SANS, 23 SAXS, 24 and gel permeation chromatography 25 measurements have been used in an attempt to obtain new insights about the aggregation behavior of these systems. Much has been learned from these studies that has advanced our understanding of the solution properties of these triblock copolymer systems.…”

Section: Introductionmentioning

confidence: 99%

Effect of Anesthetic Molecules (Halothane and Isoflurane) on the Aggregation Behavior of POE−POP−POE Triblock Copolymers

1999

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Studies of the effect of anesthetic molecules, halothane and isoflurane, on the aggregation behavior of POE-POP-POE triblock copolymers, P84, F88, P104, in aqueous solution have been carried out using fluorescence spectroscopy and light-scattering techniques. The hydrodynamic radius of block copolymer aggregates and the I/III vibronic intensity ratio of pyrene in 5 wt % aqueous solutions of F88, P84, and P104 were obtained over a wide temperature range, 10-60 °C. Large-sized clusters form at low temperatures for P104, but they do not have a well-defined hydrophobic core. Low concentrations of the anesthetics are found to induce the aggregation of F88 and P84 at 25 °C, and this effect is similar to that of increasing the temperature. The effect of halothane and isoflurane concentration on the change of hydrodynamic radius of copolymer aggregates and the I/III vibronic ratio of pyrene in F88, P84, and P104 were investigated at 25 °C. The addition of 1 mM of anesthetic is equivalent to ca. a 1-2 °C increase in temperature. It is deduced that the anesthetic molecules are distributed in both the hydrophobic core and hydrophilic corona of the polymer micelles. However, whereas an increase in temperature removes water of hydration from around the POP and POE segments, the anesthetic molecules tend to replace water of hydration around these segments. It is inferred that anesthetic molecules could disturb the water of hydration around biological macromolecules, and it is proposed that the dehydration effect of inhalation anesthetics may play an important role in the process of anesthesia.

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Restricted self-diffusion in an aqueous solution of poly(ethylene oxide) poly(propylene oxide) poly(ethylene oxide) triblock copolymer

Cited by 18 publications

References 11 publications

Study of Structure Formation in Aqueous Solutions of Poly(ethylene oxide)−Poly(propylene oxide)−Poly(ethylene oxide) Block Copolymers by Measuring Rate Constants of the Thermal Cis−Trans Isomerization of an Azobenzene Dye and Self-Diffusion of Copolymer Molecules

Study of Structure Formation in Aqueous Solutions of Poly(ethylene oxide)−Poly(propylene oxide)−Poly(ethylene oxide) Block Copolymers by Measuring Rate Constants of the Thermal Cis−Trans Isomerization of an Azobenzene Dye and Self-Diffusion of Copolymer Molecules

Influence of associations on self-diffusion of styrene-methylmethacrylate random copolymers in semidilute acetone solution

Effect of Anesthetic Molecules (Halothane and Isoflurane) on the Aggregation Behavior of POE−POP−POE Triblock Copolymers

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