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Novel Pickering emulsifiers based on pH-responsive poly(2-(diethylamino)ethyl methacrylate) latexes
A J Morse1, S P Armes, K L Thompson
1Department of Chemistry, University of Sheffield, Brook Hill, Sheffield, UK.
Langmuir : the ACS Journal of Surfaces and Colloids
|April 11, 2013
Summary
Researchers developed pH-responsive polymer latexes that act as effective Pickering emulsifiers at high pH but transition to microgels at low pH. This reversible transition enables controlled emulsion formation and demulsification, with salt-free pH control offering better reversibility.
Area of Science:
- Polymer Chemistry
- Materials Science
- Colloid and Surface Science
Background:
- Sterically stabilized polymer latexes are crucial in various applications.
- pH-responsive polymers offer tunable properties for advanced materials.
- Pickering emulsions stabilized by solid particles are gaining interest for their stability.
Purpose of the Study:
- To synthesize and characterize pH-responsive poly(ethylene glycol) methacrylate-co-2-(diethylamino)ethyl methacrylate (PEGMA-PDEA) latexes.
- To investigate the pH-induced latex-to-microgel transition and its effect on particle size.
- To evaluate the performance of PEGMA-PDEA particles as stabilizers for Pickering emulsions.
Main Methods:
- Emulsion copolymerization of PEGMA and DEA with divinylbenzene cross-linker.
- Dynamic light scattering for particle size analysis at different pH values.
- pH-dependent stability studies of oil-in-water Pickering emulsions.
Main Results:
- Near-monodisperse PEGMA-PDEA latexes (190-240 nm) were synthesized.
- A reversible latex-to-microgel transition occurred around pH 6.9.
- Particles acted as effective Pickering emulsifiers for various oils at pH 10, but demulsified upon lowering pH to 3.
- Salt-free pH control using CO2/N2 provided better reversibility than HCl/KOH adjustments.
Conclusions:
- PEGMA-PDEA particles exhibit tunable pH-responsive behavior, transitioning between latex and microgel states.
- These particles are effective, switchable Pickering emulsifiers for oil-in-water emulsions.
- The choice of pH control method impacts reversibility and response time, with gas purging offering advantages for long-term stability.
