Phase behavior and microstructures of nonionic fluorocarbon surfactant in aqueous systems
Rekha Goswami Shrestha1, Lok Kumar Shrestha, Suraj Chandra Sharma
1Graduate School of Environment and Information Sciences, Yokohama National University, Tokiwadai 79-7, Hodogaya-ku, Yokohama 240-8501, Japan.
The Journal of Physical Chemistry. B
|August 2, 2008
Summary
This study investigates the self-assembly of a fluorocarbon surfactant, C8F17EO20, in water. Adding a cosurfactant, C8F17EO1, transforms spherical micelles into wormlike micelles, altering the solution
Area of Science:
- Surfactant chemistry
- Materials science
- Physical chemistry
Background:
- Nonionic fluorocarbon surfactants exhibit unique phase behaviors in aqueous systems.
- Understanding self-assembled structures is crucial for applications in materials science and nanotechnology.
- Perfluoroalkyl sulfonamide ethoxylates represent a class of surfactants with tunable properties.
Purpose of the Study:
- To investigate the phase behavior and self-assembled structures of C8F17EO20 in aqueous solutions.
- To systematically study the influence of temperature, composition, and cosurfactant addition on micellar structure.
- To elucidate the mechanism of sphere-to-wormlike micelle transition.
Main Methods:
- Small-angle X-ray scattering (SAXS) was the primary technique for structural analysis.
- Indirect Fourier Transformation (IFT) and Generalized Indirect Fourier Transformation (GIFT) were used to analyze SAXS data.
- Rheometry was employed to confirm the formation of viscoelastic wormlike micelles.
Main Results:
- C8F17EO20 forms spherical micelles above its critical micelle concentration (cmc).
- Micellar size showed limited growth with temperature (15-75°C) due to high clouding temperature.
- Micellar structure was largely unaffected by composition (1-25 wt%) at 25°C.
- Addition of C8F17EO1 cosurfactant induced micellar growth, leading to viscoelastic wormlike micelles.
Conclusions:
- The addition of C8F17EO1 promotes the formation of wormlike micelles by increasing the critical packing parameter.
- This transition is attributed to the C8F17EO1 locating in the surfactant palisade layer, reducing headgroup area.
- The system transitions from spherical micelles to entangled wormlike micelles, forming a rigid network structure.
Related Concept Videos
01:30Micelles
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...
01:27Surface Active Agents
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...
01:29The Colloidal State
The formation of a colloidal system is exemplified by an aqueous solution containing Cl− ions is introduced to another containing Ag+ ions, resulting in the precipitation of solid AgCl as extremely tiny crystals. Instead of settling out as a filterable precipitate, these crystals remain suspended in the liquid, showcasing a colloidal system.A colloidal system involves colloidal particles within the approximate range of 1 to 1000 nm in at least one dimension, dispersed in a medium called the...
03:22Colloids
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...
03:00Solubility
Solution, Solubility, and Solubility Equilibrium
A solution is a homogeneous mixture composed of a solvent, the major component, and a solute, the minor component. The physical state of a solution—solid, liquid, or gas—is typically the same as that of the solvent. Solute concentrations are often described with qualitative terms such as dilute (of relatively low concentration) and concentrated (of relatively high concentration).
In a solution, the solute particles (molecules, atoms, and/or ions)...
A solution is a homogeneous mixture composed of a solvent, the major component, and a solute, the minor component. The physical state of a solution—solid, liquid, or gas—is typically the same as that of the solvent. Solute concentrations are often described with qualitative terms such as dilute (of relatively low concentration) and concentrated (of relatively high concentration).
In a solution, the solute particles (molecules, atoms, and/or ions)...
03:37Molecular Shape and Polarity
Dipole Moment of a Molecule