Measuring the Equilibrium Spreading Pressure—A Tale of Three Amphiphiles

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creativework.keywordsequilibrium spreading pressure, experimental protocol, monolayers, solid amphiphiles, surface dissolution, surface spreading
creativework.publisherMultidisciplinary Digital Publishing Institute (MDPI)en
dc.contributor.authorPeychev B.
dc.contributor.authorArabadzhieva D.
dc.contributor.authorMinkov I.L.
dc.contributor.authorDimitrova I.M.
dc.contributor.authorMileva E.
dc.contributor.authorSmoukov S.K.
dc.contributor.authorSlavchov R.I.
dc.date.accessioned2024-11-13T14:47:19Z
dc.date.accessioned2024-11-14T07:26:02Z
dc.date.available2024-11-13T14:47:19Z
dc.date.available2024-11-14T07:26:02Z
dc.date.issued2024-09-01
dc.description.abstractA surfactant’s equilibrium spreading pressure (ESP) is the maximum decrease in surface tension achievable at equilibrium below the Krafft point. Difficulties in measuring the ESP have been noted previously but no well-established experimental protocols to overcome them exist. We present a case study of three solid amphiphiles with different propensities to spread on the air–water interface. Starting with the partially water soluble n-dodecanol (C12H25OH), which spreads instantaneously. The strong Marangoni flows associated with the spreading result in the dislocating of the Wilhelmy plate or crystals attaching to it. A temporary mechanical barrier in front of the spreading crystals mitigates the flows disturbing the plate. Presaturating the subphase with the amphiphile prevents the establishment of dynamic steady states, reduces the standard error by a factor of three and causes faster equilibration. The perfluoroalkylated analog of dodecanol (11:1 fluorotelomer alcohol, C11F23CH2OH) is slow spreading. With surfactant crystals on the interface, the surface pressure reaches a pre-equilibrium plateau within an hour, followed by equilibration on day-long timescales. We show that it is better to estimate the ESP by averaging the values of multiple pre-equilibrium plateaus rather than waiting for equilibrium to be established. Finally, the nonspreading amphiphile DPPC exhibits a large barrier for the mass transfer from the DPPC crystal to the aqueous surface. This was overcome by introducing a volatile, water-immiscible solvent deposited on the surface next to the crystals to facilitate the spreading process and leave behind a monolayer.
dc.identifier.doi10.3390/molecules29174004
dc.identifier.issn1420-3049
dc.identifier.scopusSCOPUS_ID:85204147996en
dc.identifier.urihttps://rlib.uctm.edu/handle/123456789/1515
dc.language.isoen
dc.source.urihttps://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85204147996&origin=inward
dc.titleMeasuring the Equilibrium Spreading Pressure—A Tale of Three Amphiphiles
dc.typeArticle
oaire.citation.issue17
oaire.citation.volume29
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