Interfacial and Solution Aggregation Behavior of a Series of Bioinspired Rhamnolipid Congeners Rha-C14-Cx (x = 6, 8,...

Area of Science:

• Biochemistry
• Materials Science
• Surface Chemistry

Background:

• Rhamnolipids are microbial glycolipids with excellent surfactant properties.
• They are biodegradable and non-toxic alternatives to synthetic surfactants.
• Previous work established efficient chemical synthesis methods for rhamnolipids.

Purpose of the Study:

• To investigate how the symmetry of lipid tails in monorhamnolipids impacts their self-assembly and air/water interface adsorption.
• To explore the tunability of rhamnolipid properties through structural modifications.
• To understand the relationship between molecular structure and surfactant behavior.

Main Methods:

• Synthesis of monorhamnolipid diastereomeric mixtures (Rha-C14-Cx).
• Surface tensiometry to measure surface activity of anionic forms at pH 8.
• Dynamic light scattering and time-resolved fluorescence quenching spectroscopy to analyze aggregation behavior (hydrodynamic radius, aggregation number, morphology).

Main Results:

• Surface activity and solution aggregation behavior varied non-monotonically with changes in lipid tail symmetry.
• Aggregation characteristics such as hydrodynamic radius, aggregation number, and aggregate morphology were quantified.
• Differences in intermolecular interactions, driven by molecular structure, explain the observed variations.

Conclusions:

• Lipid tail symmetry is a critical factor influencing the self-assembly and interfacial properties of monorhamnolipids.
• The non-monotonic variation in behavior highlights the complex interplay between molecular structure and surfactant performance.
• Findings provide a basis for designing tailored biosurfactants with specific properties.