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Oleic acid-based gemini surfactants with carboxylic acid headgroups
Kenichi Sakai1, Naoki Umemoto, Wataru Matsuda
1Department of Pure and Applied Chemistry, Faculty of Science and Technology, Tokyo University of Science, Chiba, Japan. k-sakai@rs.noda.tus.ac.jp
Journal of Oleo Science
|July 20, 2011
Summary
Synthesized anionic gemini surfactants with carboxylic acid headgroups show pH-dependent behavior. They form molecular assemblies in alkaline solutions and monolayers in acidic/neutral conditions, demonstrating tunable properties for various applications.
Area of Science:
- Organic Chemistry
- Surface Chemistry
- Materials Science
Background:
- Anionic gemini surfactants offer unique properties due to their structure.
- Oleic acid is a versatile starting material for surfactant synthesis.
- pH-dependent behavior is crucial for controlling surfactant self-assembly and functionality.
Purpose of the Study:
- To synthesize novel anionic gemini surfactants from oleic acid.
- To investigate the pH-dependent physicochemical properties of these surfactants.
- To explore the influence of hydrocarbon chain length on surfactant behavior.
Main Methods:
- Synthesis of gemini surfactants via ester bond formation and disuccinyl units.
- Surface tension measurements to determine surface activity.
- Pyrene fluorescence and dynamic light scattering for studying molecular assemblies.
- Surface pressure-area isotherms and infrared external reflection for interface characterization.
Main Results:
- Surfactants exhibit pH-dependent protonation-deprotonation, influencing solubility and assembly.
- In alkaline solutions (pH 9), surfactants lower surface tension and form assemblies at low concentrations.
- In acidic/neutral conditions (pH 3-7), surfactants are insoluble and form monolayers at the air/water interface.
- Hydrocarbon chain length impacts physicochemical properties.
Conclusions:
- The synthesized anionic gemini surfactants display tunable properties based on pH.
- These surfactants can effectively reduce surface tension and form organized structures.
- Their ability to form monolayers or assemblies makes them promising for interfacial applications.
- Further research can optimize chain length for specific functionalities.
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