Effect of electrolytes on the surface behavior of rhamnolipids R1 and R2

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dc.contributor.authorHelvaci, SS
dc.contributor.authorPeker, S
dc.contributor.authorOzdemir, G
dc.date.accessioned2019-10-27T19:03:15Z
dc.date.available2019-10-27T19:03:15Z
dc.date.issued2004
dc.departmentEge Üniversitesien_US
dc.description.abstractThe surface behavior of solutions of the rhamnolipids, R1 and R2, were investigated in the absence and presence of an electrolyte (NaCl) through surface tension measurements and optical microscopy at pH 6.8. The NaCl concentrations studied are 0.05, 0.5 and 1 M. Electrolytes directly affect the carboxylate groups of the rharmolipids. The solution/air interface has a net negative charge due to the dissociated carboxylate ions at pH 6.8 with strong repulsive electrostatic forces between the rhamnolipid molecules. This negative charge is shielded by the Na+ ions in the electrical double layer in the presence of NaCl, causing the formation of a close-packed monolayer, and a decrease in CMC, and surface tension values. The maximum compaction is observed at 0.5 M NaCl concentrations for R1 and R2 monolayers, with the R1 monolayer more compact than R2. The larger spaces left below the hydrophobic tails of R1 with respect to that of R2, due to the missing second rhamnosyl groups are thought to be responsible for the higher compaction. The rigidity of both R1 and R2 monolayers increases with the electrolyte concentration. The rigidity of the R1 monolayer is greater than that of R2 at all NaCl concentrations due to the lower hydrophilic character of R1. The variation of CMC values as a function of NaCl concentration obtained from the surface tension measurements and critical packing parameter (CPP) calculations show that spherical micelles, bilayer and rod like micelles are formed in the rhamnolipid solutions as a function of the NaCl concentration. The results of optical microscopy supported these aggregation states indicating lamellar nematic liquid crystal, Cubic lamellar and hexagonal liquid crystal phases in R1 and R2 solutions depending on the NaCl concentration. (C) 2004 Elsevier B.V. All rights reserved.en_US
dc.identifier.doi10.1016/j.colsurfb.2004.01.001en_US
dc.identifier.endpage233en_US
dc.identifier.issn0927-7765
dc.identifier.issue03.Apren_US
dc.identifier.pmid15261035en_US
dc.identifier.scopusqualityQ1en_US
dc.identifier.startpage225en_US
dc.identifier.urihttps://doi.org/10.1016/j.colsurfb.2004.01.001
dc.identifier.urihttps://hdl.handle.net/11454/38097
dc.identifier.volume35en_US
dc.identifier.wosWOS:000222172100011en_US
dc.identifier.wosqualityQ2en_US
dc.indekslendigikaynakWeb of Scienceen_US
dc.indekslendigikaynakScopusen_US
dc.indekslendigikaynakPubMeden_US
dc.language.isoenen_US
dc.publisherElsevier Science Bven_US
dc.relation.ispartofColloids and Surfaces B-Biointerfacesen_US
dc.relation.publicationcategoryMakale - Uluslararası Hakemli Dergi - Kurum Öğretim Elemanıen_US
dc.rightsinfo:eu-repo/semantics/closedAccessen_US
dc.subjectrhamnolipidsen_US
dc.subjectelectrolyte effecten_US
dc.subjectsurface tensionen_US
dc.subjectcritical packing parameteren_US
dc.subjectmicelle typesen_US
dc.titleEffect of electrolytes on the surface behavior of rhamnolipids R1 and R2en_US
dc.typeArticleen_US

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