Novel pH responsive calix[8]arene hydrogelators: self-organization processes at a nanometric scale

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Polymer Chemistry

Background:

• Amphiphilic molecules are key building blocks for self-assembly.
• Hydrogels are water-swollen polymer networks with diverse applications.
• Calixarenes are a class of macrocyclic compounds with tunable properties.

Purpose of the Study:

• To investigate the formation of pH-responsive supramolecular hydrogels using water-soluble amphiphilic calix[8]arenes.
• To understand how upper rim functionalization influences hydrogelation behavior.
• To study the self-organization mechanisms of these molecules.

Main Methods:

• Synthesis of water-soluble amphiphilic calix[8]arenes.
• Hydrogelation studies at sub-millimolar concentrations.
• Atomic force microscopy (AFM) for surface analysis and self-organization visualization.

Main Results:

• Water-soluble amphiphilic calix[8]arenes form reversible supramolecular hydrogels.
• Hydrogelation is triggered by pH variations, with specific conditions (acidic or basic) depending on functionalization.
• AFM revealed insights into the self-assembly processes on charged surfaces.

Conclusions:

• pH-responsive hydrogel formation is achievable with functionalized calix[8]arenes at very low concentrations.
• The upper rim functional groups dictate the pH sensitivity and gelation conditions.
• These findings open avenues for designing smart hydrogel materials.