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General destabilization mechanism of pH-responsive Pickering emulsions
Thriveni G Anjali1, Madivala G Basavaraj
1Polymer Engineering and Colloid Science (PECS) Laboratory, Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai - 600 036, India. basa@iitm.ac.in.
Physical Chemistry Chemical Physics : PCCP
|November 15, 2017
Summary
pH-responsive particles enable tunable emulsion stability. Adjusting pH triggers particle detachment, causing emulsion destabilization, offering a reversible method for controlled demulsification in various applications.
Area of Science:
- Colloid and Surface Science
- Materials Science
- Chemical Engineering
Background:
- Pickering emulsions offer superior stability, which can be a disadvantage in applications requiring demulsification.
- Stimuli-responsive particle emulsifiers are being developed to facilitate controlled emulsion destabilization and reduce costs.
- pH-sensitive systems are attractive triggers for emulsion control due to their simplicity and ease of implementation.
Purpose of the Study:
- To investigate the destabilization mechanism of pH-switchable Pickering emulsions stabilized by particles of varying shapes and surface properties.
- To explore the role of pH-induced wettability changes in particle detachment and subsequent emulsion breakdown.
- To assess the reversibility of pH-responsive emulsion systems.
Main Methods:
- Emulsions were stabilized using hematite, silica, and polystyrene particles with different shapes and surface properties.
- Particle surface activity and wettability were tuned by adjusting the pH of the aqueous continuous phase.
- Emulsion destabilization was induced by altering the pH and observed using optical microscopy.
Main Results:
- Hematite, silica, and polystyrene particles stabilized oil-in-water (O/W) emulsions at specific pH values but destabilized them at others (e.g., pH 2, 6.5, 12).
- Emulsion destabilization occurred due to pH-induced changes in particle wettability, leading to particle detachment from droplet surfaces.
- Partially covered droplets coalesced, resulting in complete emulsion breakdown, a mechanism observed to be general for pH-responsive Pickering emulsions.
Conclusions:
- The study demonstrates a general mechanism for destabilizing Pickering emulsions using pH-responsive particles, mediated by pH-induced wettability changes and particle detachment.
- The observed pH-responsive behavior is reversible, allowing for controlled tuning of emulsion stability.
- This approach offers a convenient method to control demulsification in applications by simply adjusting the continuous phase pH, exploiting tunable particle wettability.
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