Microstructure and structural transition in microemulsions stabilized by aldonamide-type surfactants

Area of Science:

• Colloid and Surface Chemistry
• Materials Science
• Physical Chemistry

Background:

• Microemulsions are thermodynamically stable, isotropic liquid mixtures of oil, water, and surfactant.
• Understanding microemulsion structure is crucial for applications in catalysis, drug delivery, and consumer products.

Purpose of the Study:

• To characterize the microstructure and structural properties of various microemulsion types (w/o, o/w, bc).
• To investigate the influence of surfactant and cosurfactant structure on microemulsion properties.
• To determine the suitability of these microemulsions for template-based reactions and solubilizing media.

Main Methods:

• Phase diagram analysis and conductivity measurements to elucidate internal structure.
• Dynamic light scattering (DLS) for microemulsion size and polydispersity.
• Electron paramagnetic resonance (EPR), UV-vis absorption spectroscopy, and steady-state fluorescence (SSF) for microenvironment polarity and viscosity.

Main Results:

• Surfactant and cosurfactant types significantly affect microemulsion shape and extent.
• Droplet size is highly dependent on microemulsion type and cosurfactant linearity (branched vs. linear), but not surfactant alkyl chain length.
• Microemulsion droplet sizes range from 8.1–22.6 nm (o/w) and 3.7–14.3 nm (w/o).

Conclusions:

• The choice of cosurfactant is a key factor in controlling microemulsion droplet size and properties.
• These microemulsions exhibit tunable properties suitable for applications requiring specific droplet sizes and microenvironments.
• The characterized microemulsions show promise for use as templates in synthesis and as effective solubilizing agents.