Difference between revisions of "Colloid Surfactants for Emulsion Stabilization"

From Soft-Matter
Jump to: navigation, search
(Summary)
(Summary)
Line 15: Line 15:
  
 
<math>\nu=</math> "volume of the hydrophobic tail"
 
<math>\nu=</math> "volume of the hydrophobic tail"
 +
 
<math>a_0=</math> "optimum surface area of the head groups"
 
<math>a_0=</math> "optimum surface area of the head groups"
 +
 
<math>l_c=</math> "fully extended chain length of the tail"
 
<math>l_c=</math> "fully extended chain length of the tail"
 +
 
-packing parameter tells you what shape micelles form and oil in water or water in oil structures
 
-packing parameter tells you what shape micelles form and oil in water or water in oil structures
 
-vary amphiphobicity and geometry
 
-vary amphiphobicity and geometry
  
 
== Soft Matter Details ==
 
== Soft Matter Details ==

Revision as of 02:14, 28 October 2009

Overview

  • [1] Kim, J., Lee, D., Shum, H., & Weitz, D. Adv. Mater. 20, 3239-3243 (2008).

Summary

Kim, Lee, Shum, and Weitz use solid particles in the place of surfactant molecules and qualitatively compare both methods of stabilizing emulsions. Emulsions stabilized with particles are called Pickering emulsions.

Figure 1. Geometry of the fabricated particles. From figure 1 of [1].

The solid particles that the researchers fabricate look like two connected spheres of different radii (see figure 1). Surprisingly, these particles are not formed by connecting two pre-existing spheres. Rather, Kim et. al. heat crosslinked polystyrene spheres which have been "swollen" with styrene and a couple other chemicals. The heat causes an elastic stress on the spheres which causes the spheres to squeeze out some of the material inside them. The first sphere shrinks, and a new, attached sphere grows. This process is called the "seeded monomer swelling and polymerization technique."

The reason for creating dimer particles rather than spheres is to allow control over the particle's geometry as well as chemistry. A molecular surfactant's aggregation structure (micelle, vesicle, bilayer, or inverted micelle) depends on its packing parameter <math>P_{packing}</math> which in turn depends on the geometry of the molecule.


<math>P_{packing}=\frac{\nu}{a_0l_c}</math>

<math>\nu=</math> "volume of the hydrophobic tail"

<math>a_0=</math> "optimum surface area of the head groups"

<math>l_c=</math> "fully extended chain length of the tail"

-packing parameter tells you what shape micelles form and oil in water or water in oil structures -vary amphiphobicity and geometry

Soft Matter Details