pH-responsive anionic wormlike micelle based on sodium oleate induced by NaCl.
Hongsheng Lu1, Qianping Shi, Zhiyu Huang
1School of Chemistry and Chemical Engineering, Southwest Petroleum University , Xindu, Sichuan 610500, P. R. China.
The Journal of Physical Chemistry. B
|October 23, 2014
Summary
This study introduces a pH-responsive wormlike micellar system using sodium oleate and NaCl. The system transitions between gel-like and fluid states, offering tunable viscoelastic properties for potential applications.
Area of Science:
- Materials Science
- Colloid and Surface Chemistry
Background:
- Anionic surfactant solutions, like sodium oleate (NaOA), can form complex structures.
- Controlling micellar structure is key for developing advanced materials with tunable properties.
Purpose of the Study:
- To develop a pH-responsive wormlike micellar system using sodium oleate and NaCl.
- To investigate the reversible transformation between wormlike and spherical micelles induced by pH changes.
Main Methods:
- Rheological measurements (steady and dynamic) to characterize viscoelasticity.
- Dynamic light scattering, cryo-transmission electron microscopy (cryo-TEM), and nuclear magnetic resonance (NMR) for structural analysis.
- Systematic variation of pH and NaCl concentration to study responsiveness.
Main Results:
- Sodium oleate solutions formed high-viscoelastic wormlike micelles at 200-350 mM NaCl.
- The system exhibited prompt, reversible switching between gel-like and fluid states within a narrow pH range.
- Structural transitions between wormlike and spherical micelles were confirmed across different pH values.
Conclusions:
- The pH-responsive behavior is driven by the ionization state of the carboxylate group in sodium oleate.
- At higher pH, ionized carboxylate promotes wormlike micelle formation with NaCl.
- At lower pH, sodium oleate converts to oleic acid, leading to spherical micelle formation due to weaker interactions.
More Related Videos
Related Concept Videos
01:30Micelles
313
Micelle formation is an intricate process that hinges on the properties of amphiphilic or amphipathic molecules and the conditions of the system in which they are found. Amphiphilic molecules, which have both hydrophilic (water-attracting) and hydrophobic (water-repelling) parts, play a critical role in this process.In aqueous environments, these molecules arrange themselves such that their hydrophilic heads are turned towards the water phase, while their hydrophobic tails are oriented away...
313
03:22Colloids
17.1K
Children at play often make suspensions such as mixtures of mud and water, flour and water, or a suspension of solid pigments in water known as tempera paint. These suspensions are heterogeneous mixtures composed of relatively large particles that are visible to the naked eye or can be seen with a magnifying glass. They are cloudy, and the suspended particles settle out after mixing. On the other hand, a solution is a homogeneous mixture in which no settling occurs and in which the dissolved...
17.1K
01:27Surface Active Agents
141
Surfactants, named for their behavior at interfaces, positively adsorb at the interfaces of two phases, reducing interfacial tension. Their versatility as emulsifiers, detergents, and foaming agents stems from this ability. Surfactants, often termed amphiphiles, share the property of amphipathy, with molecules having both hydrophilic and hydrophobic portions. The hydrophilic part is called the head, and the hydrophobic part, including an elongated alkyl substituent, forms the tail.Surfactants...
141