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pH-Switchable Surfactant-Based Microemulsions: Reversible Transition between Microemulsification and Demulsification
Bo Zhu1, Hui Chen1, Liwen Shi1,2
1Key Laboratory of Synthetic and Biological Colloids, Ministry of Education, School of Chemical & Materials Engineering, Jiangnan University, Wuxi 214122, P. R. China.
Langmuir : the ACS Journal of Surfaces and Colloids
|November 14, 2024
Summary
This study introduces the first pH-switchable surfactant-based microemulsion (SBME) using SDS-C12A, enabling reversible phase transitions for applications like recyclable reaction media.
Area of Science:
- Materials Science
- Colloid and Surface Chemistry
Background:
- pH-switchable surfactant-based microemulsions (SBMEs) offer reversible phase transitions, a rarely reported phenomenon.
- Controlling microemulsion stability via pH is crucial for advanced material applications.
Purpose of the Study:
- To fabricate and characterize the first pH-switchable SDS-C12A-based microemulsion (SDS-C12A-ME).
- To investigate the mechanism of reversible switching and the impact of byproducts.
- To demonstrate the potential of SDS-C12A-ME as a recyclable reaction medium.
Main Methods:
- Fabrication of SDS-C12A-ME using an equimolar mixture of sodium dodecyl sulfate and N,N-dimethyldodecylamine.
- Investigation of reversible switching triggered by alternating acids and bases.
- Assessment of byproduct effects (H2O and salt) on reversibility.
- Demonstration using methyl methacrylate photochemical polymerization as a model system.
Main Results:
- Successfully fabricated the first pH-switchable SDS-C12A-ME.
- Reversible switching relies on the protonation/deprotonation of C12A, affecting the emulsifier film.
- Salt byproducts significantly reduce reversibility; choline hydroxide enhances switching cycles compared to sodium hydroxide.
- The SDS-C12A-ME served as a recyclable reaction medium for polymerization, yielding poly(methyl methacrylate) with reproducible molecular weight and narrow polydispersity (PDI ≈ 1.2).
Conclusions:
- The developed SDS-C12A-ME exhibits efficient pH-switchable behavior.
- Optimized acid-base stimuli (e.g., HCl-ChOH) enhance reversibility and cycling stability.
- pH-switchable microemulsions are promising recyclable media for polymerization and potentially other applications like drug delivery and microreactors.
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