Surface properties of inclusion complexes between alpha-cyclodextrin and poly(ethylene oxide).

Area of Science:

• Supramolecular chemistry
• Polymer science
• Surface chemistry

Background:

• Supramolecular inclusion complexes (IC) formed by threading alpha-cyclodextrin (alpha-CD) onto poly(ethylene oxide) (PEO) are relevant in various applications.
• Understanding the surface properties of these ICs is crucial for predicting their behavior in solution and at interfaces.

Purpose of the Study:

• To characterize the surface properties of alpha-cyclodextrin/poly(ethylene oxide) inclusion complexes (IC).
• To compare the surface activity and wettability of ICs with their individual components (alpha-CD and PEO).
• To determine the adsorption behavior and driving forces at the air/aqueous interface.

Main Methods:

• Characterization using IR, (1)H NMR spectroscopy, and thermal analysis.
• Interfacial tension measurements as a function of IC concentration and temperature.
• Static contact angle measurements to determine wettability and hydrophobicity.
• Application of the Gibbs equation to quantify adsorption.

Main Results:

• Alpha-cyclodextrin (alpha-CD) alone does not exhibit surface activity.
• The inclusion complex (IC) shows increased hydrophobicity compared to both PEO and alpha-CD.
• Adsorption of the IC at the air/aqueous interface is driven by an enthalpic contribution.
• Interfacial tension variations were quantified with concentration and temperature.

Conclusions:

• The supramolecular inclusion complex formation significantly alters the surface properties compared to individual components.
• The enhanced hydrophobicity of the IC suggests potential applications where surface interactions are critical.
• Enthalpic factors play a key role in the adsorption of these complexes at interfaces.