Interactions in mixed cationic surfactants and dextran sulfate aqueous solutions

Area of Science:

• Supramolecular Chemistry
• Polymer Science
• Physical Chemistry

Background:

• Dextran sulfate is a hydrophilic anionic polysaccharide.
• N-alkylammonium chlorides are oppositely charged surfactants with varying alkyl chain lengths (C10, C12, C14).
• Understanding these interactions is crucial for designing novel materials and formulations.

Purpose of the Study:

• To investigate the complex formation between dextran sulfate and n-alkylammonium chlorides.
• To determine the influence of surfactant alkyl chain length on aggregation behavior and structure.
• To characterize the resulting supramolecular structures.

Main Methods:

• Optical microscopy
• X-ray diffraction
• Microelectrophoretic mobility
• Conductivity measurements
• Surface tension measurements
• Light-scattering measurements

Main Results:

• Increasing surfactant alkyl chain length decreased both critical aggregation concentration (cac) and critical micelle concentration (cmc).
• Light-scattering and microelectrophoretic data indicated the coexistence of diverse complexes beyond cac.
• X-ray diffraction revealed lamellar structures in dry complexes, with increasing thickness and decreasing bilayer number as alkyl chain length increased.
• Giant vesicles suggested bilayer ordering in at least one species.

Conclusions:

• The interactions lead to the formation of ordered multilamellar structures.
• Surfactant chain length is a key factor controlling the aggregation behavior and structural organization.
• These findings provide insights into the self-assembly of polysaccharide-surfactant systems.