pH-responsive surface activity and solubilization with novel pyrrolidone-based Gemini surfactants

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Physical Chemistry

Background:

• Gemini surfactants are a class of molecules with unique properties due to their structure.
• pH-responsive surfactants are valuable for applications where controlled release or activity is needed.
• 2-pyrrolidone head groups offer specific chemical characteristics for surfactant design.

Purpose of the Study:

• To synthesize and characterize novel pH-responsive Gemini surfactants with 2-pyrrolidone head groups (Di-C(n)P).
• To investigate the surface activity and micellization behavior of these surfactants under varying pH conditions.
• To explore the potential of these surfactants for pH-tunable solubilization applications.

Main Methods:

• Synthesis of N,N'-dialkyl-N,N'-di(ethyl-2-pyrrolidone)ethylenediamine (Di-C(n)P) surfactants.
• Characterization using NMR spectroscopy ((1)H, (13)C), ESI-MS, and elemental analysis.
• Evaluation of surface activity and micellization via equilibrium surface tension and fluorescence spectroscopy across different pH values.

Main Results:

• The synthesized Di-C(n)P surfactants exhibit pH-dependent surface activity due to protonation.
• These novel Gemini surfactants show lower critical micelle concentration (cmc) and surface tension at cmc (γ(cmc)) compared to conventional cationic and nonionic Gemini surfactants.
• Fluorescence data confirm micelle formation above the cmc, and preliminary results demonstrate pH-tunable solubilization of cyclohexane.

Conclusions:

• The new series of pH-responsive Gemini surfactants (Di-C(n)P) with 2-pyrrolidone head groups have been successfully synthesized and characterized.
• Their surface activity and micellization behavior are significantly influenced by pH, offering tunable properties.
• The pH-tunable micellization and solubilization capacity of Di-C(n)P surfactants present promising applications in areas like microemulsions and controlled solubilization.