A Calorimetry and Light Scattering Study of the Formation and Shape Transition of Mixed Micelles of EO20PO68EO20Triblock Copolymer (P123) and Nonionic Surfactant (C12EO6)

Löf, David; Niemiec, Anna; Schillén, Karin; Loh, Watson; Olofsson, Gerd

doi:10.1021/jp071101n

Cited by 90 publications

(66 citation statements)

References 55 publications

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“…In addition, the raw calorimetric curves, also shown as inset in Figure 3, indicated that, around this special molar ratio, the peaks were composed by a fast endothermic and a slow exothermic process, taking around 15-20 min to equilibrate. The same time dependence was observed for structural measurements using light and small-angle X-ray scattering techniques [13].…”

supporting

confidence: 54%

Calorimetry is not color-blind. Molecular insights on association processes in surfactant-polymer mixtures derived from calorimetric experiments

Loh

Brinatti

2011

Sci. China Chem.

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This comment will review and discuss recent results obtained with the use of calorimetry in assessing molecular information from complex phenomena such as association in surfactant/polymer mixtures. These examples were selected to support the view that it is possible to ally the great sensitivity of modern calorimeters with carefully planned experiments and, sometimes, ancillary techniques in order to derive detailed information on molecular interactions. calorimetry, polymer-surfatant interaction, self-assemblyCalorimetry is one of the earliest quantitative techniques employed in chemical and biological experiments, such as those developed by Lavoisier in the search for the origins of life [1], or in Watt's experiments on the relationship between heat and work. Nowadays, it is mostly used when high sensitivity is required, such as in the investigation of processes occurring in rather dilute solutions, as in the cases of biological interactions involving minute amounts of either biomolecules or drugs [2]. Recent developments in the design of calorimeters provide striking sensitivity, which allied to the general nature of heat exchange, produce a universal and very sensitive sensor to detect or monitor almost all chemical and biological processes. However, this detection is not selective in the sense that calorimeters are not capable of distinguishing the origin of exchanged heat, as opposed, for instance, to spectroscopic techniques which may follow the formation/breakdown of a specific chemical bond, release of a specific molecule fragment or chemical changes. This lack of selectivity leads to the current saying that heat bears no color, a conclusion that would encompass calorimetry as a technique incapable of providing information at the molecular level. We believe this is not true and we will discuss below a few examples that reveal the capacity of calorimetric experiments not only detecting features that may not be observable otherwise, but also providing insights at the molecular level.Calorimetry is now widespread in the investigation of other complex (chemical) systems, such as mixtures containing self-assembling molecules like surfactants and polymers. These studies are typically conducted in the titration mode, in which concentration of one of the components is increased, at constant temperature, named ITC (Isothermal Titration Calorimetry), producing information on the thermodynamics of these binding process--in this case, calorimetry is the only technique that allows the derivation of Gibbs energy, enthalpy and entropy changes from a unique experiment. Alternatively, experiments may be planned in the scanning mode (DSC-Differential Scanning Calorimetry) in which energy changes accompanying temperature driven processes are probed at constant composition.The use of calorimetry for investigation of association processes involving surfactants and/or polymers has been reviewed in recent articles [3][4][5], which in general indicate an increase of the use of these techniques, mostly due to the

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confidence: 54%

Calorimetry is not color-blind. Molecular insights on association processes in surfactant-polymer mixtures derived from calorimetric experiments

Loh

Brinatti

2011

Sci. China Chem.

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“…Thus, although nonionic surfactants are generally known not to interact with nonionic polymers, some articles describe strong interactions taking place in specific systems constituted by C 12 EO 6 and a wide range of Pluronics [22][23][24]. The C 12 EO 6 structure is quite similar to Rewopal X1207L and this synergistic behavior may be extrapolated to our system.…”

Section: Association Of Pluronic P123 With Rewopal X1207lmentioning

confidence: 75%

Acidic surfactant solutions for tributylphosphate removal in nuclear fuel reprocessing plants: A formulation study

Causse

Faure

2009

Chemical Engineering Journal

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“…The presence of this composite peak is attributed to the formation of vesicles or a dispersion of a lamellar liquid crystal in a two-step process [57]. It is known that the enthalpy change of pure L121 solutions is related with the aggregation process, and results from the dehydration of PPO chains [57]. Below a certain temperature (i.e.…”

Section: Dsc Measurementsmentioning

confidence: 99%

“…Actually, the formation of micelles in other Pluronic aqueous solutions is reflected by a single peak, as in the present case when AOT is added. In L121 + sodium dodecyl sulfate (SDS) mixed systems, the micellization enthalpy also decreases upon adding the ionic surfactant, but the onset temperature actually increases [57]. AOT is much less hydrophilic than SDS, and therefore the effect should be different.…”

Section: Dsc Measurementsmentioning

confidence: 99%

Erratum to: Solution behavior of aqueous mixtures of low and high molecular weight hydrophobic amphiphiles

et al. 2010

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Mixtures of a hydrophobic triblock copolymer (L121, PEO 5 PPO 68 PEO 5 ) and a hydrophobic anionic surfactant (AOT, Sodium bis(2-ethylhexyl)sulfosuccinate), each alone forming turbid vesicular solutions in water, aggregate to produce a thermodynamically stable, transparent and isotropic solution. Mixed AOT/L121 aggregates could be confirmed by fluorescence, surface tension, differential scanning calorimetry (DSC) and isothermal titration calorimetry (ITC). In an isotropic region, where mixed aggregates are formed, there is a synergistic interaction between monomers of AOT and L121 in the mixture. In addition, Small Angle Neutron Scattering (SANS) experiments provided evidence that mixed aggregates have the shape of either spheres (with a certain polydispersity) or very short ellipsoids (axial ratio below 2), confirming a transition from giant multilamellar vesicles to small aggregates upon mixing the two hydrophobic amphiphiles. Upon dilution, the morphology changes to disk-like. From an examination of the results of all the methods the peculiar behavior of the mixed AOT/L121 system is explained.The online version of the original article can be found at http://dx.doi.

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A Calorimetry and Light Scattering Study of the Formation and Shape Transition of Mixed Micelles of EO₂₀PO₆₈EO₂₀Triblock Copolymer (P123) and Nonionic Surfactant (C₁₂EO₆)

Cited by 90 publications

References 55 publications

Calorimetry is not color-blind. Molecular insights on association processes in surfactant-polymer mixtures derived from calorimetric experiments

Calorimetry is not color-blind. Molecular insights on association processes in surfactant-polymer mixtures derived from calorimetric experiments

Acidic surfactant solutions for tributylphosphate removal in nuclear fuel reprocessing plants: A formulation study

Erratum to: Solution behavior of aqueous mixtures of low and high molecular weight hydrophobic amphiphiles

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