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Mixing Behavior in Binary Anionic Gemini Surfactant-Perfluorinated Fatty Acid Langmuir Monolayers
Jeveria Rehman1, David Sowah-Kuma1, Amy L Stevens1
1Department of Chemistry, University of Saskatchewan , Saskatoon, SK, Canada.
Langmuir : the ACS Journal of Surfaces and Colloids
|September 6, 2017
Summary
This study shows that an anionic gemini surfactant and perfluorotetradecanoic acid form miscible mixed Langmuir monolayers with attractive interactions. The surfactant disrupts the crystalline structure of the perfluorinated acid, altering film morphology.
Area of Science:
- Supramolecular Chemistry
- Materials Science
- Surface Chemistry
Background:
- Langmuir monolayers are crucial for studying molecular interactions at interfaces.
- Gemini surfactants and perfluorinated acids exhibit unique self-assembly properties.
- Understanding mixed monolayers informs the design of advanced materials.
Purpose of the Study:
- Investigate miscibility and film structure of mixed Ace(12)-2-Ace(12) gemini surfactant and perfluorotetradecanoic acid (PF) Langmuir monolayers.
- Characterize the interactions and structural transformations in these mixed systems.
- Compare findings with other mixed surfactant systems.
Main Methods:
- Thermodynamic characterization of mixed monolayers.
- Structural analysis of film morphology at the air-water interface.
- Surface pressure-area (π-A) isotherms and compressibility measurements.
Main Results:
- Miscibility observed between Ace(12)-2-Ace(12) and PF over a range of compositions, indicating attractive interactions.
- Pure PF forms crystalline hexagonal lattices; pure gemini surfactant forms amorphous films.
- Mixed films show a loss of PF crystallinity below a PF:surfactant mole ratio of 2.5, with altered structures at higher PF fractions.
Conclusions:
- The gemini surfactant Ace(12)-2-Ace(12) and PF are miscible, forming stable mixed monolayers.
- Attractive interactions drive miscibility and significantly alter the self-assembly behavior of PF.
- The study provides insights into structure-property relationships in mixed fluorinated and non-fluorinated surfactant systems.