Hierarchical assembly of pH-responsive surfactant-cyclodextrin complexes.

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Physical Chemistry

Background:

• Surfactants and cyclodextrins are key components in supramolecular chemistry.
• Understanding their complexation and self-assembly is crucial for designing novel materials.

Purpose of the Study:

• Investigate the inclusion complexation of alkyl ethoxy carboxylates with alpha-cyclodextrin (αCD) and beta-cyclodextrin (βCD).
• Determine the thermodynamic driving forces and pH dependence of the complexation process.
• Characterize the self-assembly behavior and morphology of the resulting supramolecular aggregates.

Main Methods:

• Isothermal titration calorimetry (ITC) and volumetry to study complexation thermodynamics.
• Small-angle neutron scattering (SANS), electron microscopy, and optical microscopy to probe aggregate morphology.
• Analysis of surfactant degree of ionization and ethylene oxide chain length.

Main Results:

• Complexation is an enthalpically driven and pH-independent process for both αCD and βCD.
• Spontaneous self-assembly into highly ordered supramolecular aggregates was observed.
• Non-ionized systems formed thin platelets, while ionized systems formed multilayered hollow cylinders.
• Aggregate morphology is influenced by the number of ethylene oxides and cyclodextrin cavity size.

Conclusions:

• The study reveals controllable hierarchical self-assembly of surfactant-cyclodextrin complexes.
• Tuning parameters like surfactant structure and cyclodextrin type significantly impact aggregate morphology.
• This work provides insights into controlling supramolecular assembly through tailored interactions.