Vesicle-to-micelle transition in dioctadecyldimethylammonium bromide and dioctadecyldimethylammonium chloride dispersions induced by octaethylene glycol n-dodecyl monoether. An isothermal titration calorimetry study

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dc.contributor.authorBarreleiro, P. C.A.
dc.contributor.authorOlofsson, G.
dc.contributor.authorFeitosa, E. [UNESP]
dc.contributor.institutionUniversity of Lund
dc.contributor.institutionUniversidade Estadual Paulista (UNESP)
dc.date.accessioned2022-04-28T19:55:04Z
dc.date.available2022-04-28T19:55:04Z
dc.date.issued2000-12-01
dc.description.abstractWe have used isothermal titration calorimetry to investigate the vesicle-to-micelle transition in dioctadecyldimethylammonium bromide (DODAB) and chloride (DODAC) vesicle dispersions induced by the nonionic surfactant octaethylene glycol n-dodecyl monoether (C12E8) at room temperature. Small and giant unilamellar vesicles were prepared by sonication and without sonication, respectively, of the pure cationic surfactants at low concentrations in water. The titration of 1.0 mM DODAX (X = Cl- and Br-) by a concentrated micellar solution of C12E8 shows that the enthalpy of interaction (ΔHobs) of C12E8 in micellar form with DODAX is always endothermic. The titration curves are understood on the basis of superposition of the enthalpies of partitioning of C12E8 into the bilayer, of micelle formation and of vesicle-to-micelle transformation. The enthalpy, ΔHobs, initially increases owing to the incorporation of C12E8 into the vesicle bilayer until the C12E8/DODAX saturation ratio (Rsat) is reached, then ΔHobs decreases, in different ways for DODAB and DODAC, owing to degradation of vesicles and formation of mixed micelles and intermediary structures up to the C12E8/ DODAX solubilization ratio, Rsol. Above Rsol only mixed micelles exist. The surfactant solubilization takes place in three stages. All the critical ratios are lower for DODAB than for DODAC, meaning that C12E8 solubilizes more strongly in DODAB; for example, Rsat is 0.8 for DODAB and 1.2 for DODAC. Sonication has no significant effect on the transition. © Springer-Verlag 2000.en
dc.description.affiliationPhysical Chemistry 1 Center for Chemistry and Chemical Engineering University of Lund, P.O. Box 124, 221 00 Lund
dc.description.affiliationPhysics Department IBILCE/UNESP, 15054-000 Sao Jose do Rio Preto, SP
dc.description.affiliationUnespPhysics Department IBILCE/UNESP, 15054-000 Sao Jose do Rio Preto, SP
dc.format.extent33-36
dc.identifier.citationProgress in Colloid and Polymer Science, v. 116, p. 33-36.
dc.identifier.issn0340-255X
dc.identifier.scopus2-s2.0-0034591941
dc.identifier.urihttp://hdl.handle.net/11449/224187
dc.language.isoeng
dc.relation.ispartofProgress in Colloid and Polymer Science
dc.sourceScopus
dc.subjectCationic vesicles
dc.subjectDioctadecyldimethylammonium bromide
dc.subjectDioctadecyldimethylammonium chloride
dc.subjectIsothermal titration calorimetry
dc.subjectSurfactant solubilization
dc.titleVesicle-to-micelle transition in dioctadecyldimethylammonium bromide and dioctadecyldimethylammonium chloride dispersions induced by octaethylene glycol n-dodecyl monoether. An isothermal titration calorimetry studyen
dc.typeArtigo

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