Probing the size of Pluronic P84 block copolymer micelles in aqueous solution by means of positron annihilation lifetime spectroscopy

Bockstahl, Fre ́de ́ric; Duplâtre, G.; Miguel, Maria G.

doi:10.1039/b002969f

Cited by 10 publications

(9 citation statements)

References 19 publications

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“…To avoid any distortion in the spectra due to non-Gaussian distribution of the counts in each channel, the integrated counts were kept at about 10 6 . [10,11] The temperature range (25.0-50.08C) was investigated by using a thermostatically controlled copper vessel, with an accuracy of +0.18C. After changing the temperature, the device was maintained for 30 min to make the sample solution equilibrate at that temperature.…”

Section: Methodsmentioning

confidence: 99%

Unique Free‐Volume Change During the Phase Separation of Poly(N‐isopropylacrylamide) Aqueous Solution Studied by Positron Annihilation Lifetime Spectroscopy

Zhang

Chen

et al. 2007

Spectroscopy Letters

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The change in free-volume during phase separation of poly(N-isopropylacrylamide) (PNIPAM) aqueous solution was studied in situ by positron annihilation lifetime spectroscopy. The average size of a free-volume nanohole exhibited a co-nonsolvent change, affirming the trans-to-gauche conformational change of PNIPAM chains during phase separation. The results obtained for the ortho-positron (o-Ps) intensity accounted for the competitive effects of the variations in composition of the free C5 5O group and the free amino group on the o-Ps formation.

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Section: Methodsmentioning

confidence: 99%

Unique Free‐Volume Change During the Phase Separation of Poly(N‐isopropylacrylamide) Aqueous Solution Studied by Positron Annihilation Lifetime Spectroscopy

Zhang

Chen

et al. 2007

Spectroscopy Letters

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“…The poly(ethyleneglycol) (PEG, average molar weight 600) and duroquinone, from Aldrich, and the triblock copolymer P84, from BASF, all AR grade and used as received, were from the same batches as previously used. 10 The aqueous solutions were made by weighing the appropriate quantities of chemicals, then dissolving in water with a resistivity of 18 MO cm. Two types of solutions were prepared in the present experiments: 3.57 wt% PEG (59.5 mM) and 12.5 wt% P84 (as used in previous experiments) 8,10 with additional duroquinone concentrations of 0, 0.5, 1 and 2 mM.…”

Section: Methodsmentioning

confidence: 99%

“…10 The aqueous solutions were made by weighing the appropriate quantities of chemicals, then dissolving in water with a resistivity of 18 MO cm. Two types of solutions were prepared in the present experiments: 3.57 wt% PEG (59.5 mM) and 12.5 wt% P84 (as used in previous experiments) 8,10 with additional duroquinone concentrations of 0, 0.5, 1 and 2 mM. Table 1 gathers some characteristics of the various chemicals used.…”

Section: Methodsmentioning

confidence: 99%

“…7 The P84 micelles have been previously studied as a function of temperature through neutron (SANS) 8 and light 9 scatterings. However, both studies were limited to temperatures not exceeding 333 K, the reason for this probably lying in the fact that the system undergoes gelification at about 334 K. A later study by PALS 10 was also limited to below 333 K, because of the previous need, commented above, to know either R core or N ag .…”

Section: Introductionmentioning

confidence: 99%

“…To limit the number of fitting parameters and the correlations between them, we deemed it useful to measure independently the o-Ps lifetime in the water bulk. To take account of the presence of the PEO chains, the same solution as previously used 10 was therefore studied as a function of temperature: 59.5 mM (3.57 wt%) poly(ethyleneglycol), PEG, whose concentration is the same as that of the PEO chains in the P84 solution.…”

Section: Introductionmentioning

confidence: 99%

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Behaviour of Pluronic® P84 block copolymer micelles above the gelification temperature as probed by positron annihilation lifetime spectroscopy

Messaoud

Duplâtre

Waton

et al. 2005

Phys. Chem. Chem. Phys.

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The new method based on positron annihilation lifetime spectroscopy (PALS) to determine both the mean core radius, R(core), and aggregation number, N(ag), of micelles is applied to the study of aqueous solutions of the triblock Pluronic P84 copolymer as a function of temperature (T), beyond the gelification point (334 K). Two long-lived components appear in the PALS spectra, ascribed to triplet positronium in the water bulk (o-Ps(aq)) and in the organic core of the micelles (o-Ps(org)). Of the various fitting parameters, only the lifetime of the latter species, tau4, and the micellar parameters, R(core) and N(ag), disclose the occurrence of gelification by first increasing up to 334 K, then decreasing. By contrast to what is known in case of phase transition, none of the parameters shows any abrupt change at 334 K, whereas the macroscopic viscosity of the solutions suffers a drastic increase. This is attributed to the fact that positronium is sensitive to the microviscosity of the solutions. At the transition point, the properties of the polyoxipropylene aggregates forming the organic core of the P84 micelles are not greatly affected. Furthermore, the fact that the experimental N(ag) values coincide with those calculated for spheres, from the R(core) values, indicates that the shape of the P84 cores does not change significantly after gelification. The onset of gelification results from a decrease in the hydrogen bonding interactions in the solution with an ensuing relative increase in the interactions between the polyoxipropylene (PPO) groups, initially forming the corona of the P84 micelles, in an intermicellar mode. This increased solicitation of the PPO groups outside their initial location would result in depletion in the number of surfactant molecules forming the micelles, viz. a decrease in both R(core) and N(ag) above 334 K. From the data, additional information can be gained regarding the local viscosity and surface tension in the micellar cores.

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Micelle morphology and chain conformation of triblock copolymers under shear: LA-DPD study

Prhashanna

Khan

Chen

2016

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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Probing the size of Pluronic P84 block copolymer micelles in aqueous solution by means of positron annihilation lifetime spectroscopy

Cited by 10 publications

References 19 publications

Unique Free‐Volume Change During the Phase Separation of Poly(N‐isopropylacrylamide) Aqueous Solution Studied by Positron Annihilation Lifetime Spectroscopy

Unique Free‐Volume Change During the Phase Separation of Poly(N‐isopropylacrylamide) Aqueous Solution Studied by Positron Annihilation Lifetime Spectroscopy

Behaviour of Pluronic® P84 block copolymer micelles above the gelification temperature as probed by positron annihilation lifetime spectroscopy

Micelle morphology and chain conformation of triblock copolymers under shear: LA-DPD study

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