Salt dependent stability of stearic acid Langmuir-Blodgett films exposed to aqueous electrolytes
We use contact angle goniometry, imaging ellipsometry, and atomic force microscopy to study the stability and wettability of Langmuir-Blodgett (LB) monolayers of stearic acid on silica substrates, upon drying and exposure to aqueous solutions of varying salinity. The influences of Ca(2+) and Na(+) i...
| Veröffentlicht in: | Langmuir : the ACS journal of surfaces and colloids. - 1992. - 29(2013), 17 vom: 30. Apr., Seite 5150-9 |
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| 1. Verfasser: | |
| Weitere Verfasser: | , , , |
| Format: | Online-Aufsatz |
| Sprache: | English |
| Veröffentlicht: |
2013
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| Zugriff auf das übergeordnete Werk: | Langmuir : the ACS journal of surfaces and colloids |
| Schlagworte: | Journal Article Research Support, Non-U.S. Gov't Electrolytes Salts Stearic Acids Water 059QF0KO0R stearic acid 4ELV7Z65AP Silicon Dioxide mehr... |
| Zusammenfassung: | We use contact angle goniometry, imaging ellipsometry, and atomic force microscopy to study the stability and wettability of Langmuir-Blodgett (LB) monolayers of stearic acid on silica substrates, upon drying and exposure to aqueous solutions of varying salinity. The influences of Ca(2+) and Na(+) ions are compared by varying their concentrations, both in the subphase before the LB transfer, and in the droplets to which the dried LB layers are exposed. Ca(2+) ions in the subphase are found to enhance the stability, leading to contact angles up to 100°, as compared to less than 5° for Na(+). Consistent with the macroscopic wettability, AFM images show almost intact films with few holes exposing bare substrate when prepared in the presence of Ca(2+), while subphases containing Na(+) result in large areas of bare substrate after exposure to aqueous drops. The observations on varying the composition of the droplets corroborate the stabilizing effect of Ca(2+). We attribute these findings to the cation-bridging ability of Ca(2+) ions, which can bind the negatively charged stearate groups to the negatively charged substrates. We discuss the relevance of our findings in the context of enhanced oil recovery |
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| Beschreibung: | Date Completed 11.11.2013 Date Revised 21.11.2013 published: Print-Electronic Citation Status MEDLINE |
| ISSN: | 1520-5827 |
| DOI: | 10.1021/la400615j |