What is a Colloid?

1. What is a Colloid? Intermediate between a true solution and a suspension High molecular weight Aggregate into large particles, ~micron Finely divided (“isolated”) dispersions

2. What is a Colloid? What is Cool Whip? Whipped toppings are essentially an emulsion of oil (usually around 35%) and sweetened water (around 60%) with an emulsifier, like phosphatidyl choline (lecithin), to maintain the suspension. The oil used for whipped toppings, like Cool Whip™, is hydrogenated vegetable oil, and after hydrogenation (saturation with hydrogen), all vegetable oils are the same (saturated), regardless of where they come from. So hydrogenated olive oil could easily be used to make whipped toppings.

3. What is Cool Whip? Oils (and fats) are fatty acids—phospholipids—have two parts (as their name suggests): a phosphate "head", and a long hydrocarbon "tail" (the fatty part). “tail” “head”

4. What is Cool Whip? An emulsion of oil and water is really just water with microscopic oil droplets floating in it (this is called a colloidal suspension). To get the oil to form these droplets, called micelles, the molecules of fatty acid have to pack together as closely as possible to minimize the volume of the micelle. To form a micelle, the heads of the molecules, which are soluble, form the outside of the drop, while the tails fill the inside. micelle Lots of micelles suspended in water No water wants to be here!

5. What is Cool Whip? The defining characteristic of unsaturated fats is that their tails have kinks in them. These kinks prevent the molecules from packing close together, so they tend to disrupt the micelles - the more unsaturated fats, the fewer and larger the micelles. Without good micelles, the emulsion will separate into its two phases (oil and water), and without a good emulsion, you can't whip the suspension into a dessert topping. kinks

6. What is Cool Whip? The unsaturated fats have tails have kinks that prevent the molecules from packing close together, so they tend to disrupt the micelles - the more unsaturated fats, the fewer and larger the micelles. Compare to a saturated— hydrogenated— fat

7. Micelles in Medicine Example 1. self-forming micelles by an eczema drug http://www2.cnrs.fr/en/1043.htm?debut=72

8. Designer Micelles – Block Co-Polymer Note use of weight% “On the basis of examples already found in literature, one unifying rule for generating polymersomes predicts that f (the weight percent of the hydrophilic block) must be equal to 35±10%. Molecules with f >45% are expected to form spherical micelles, whereas molecules with f <25% are expected to form inverted nanostructures. When the weight percent of the hydrophilic block f >45 % : micelles form When the weight percent of the hydrophilic block f ~ 35 % : vesicles (polymersomes) form

9. S. Lecommandoux, M. F. Achard, J. F. Langenwalter, H.-A. Klok Macromolecules 34(26), 9100-9111 (2001) http://recherche.enscpb.fr/lcpo/

10. Different realm of colloid investigation: Dynamics of micelle monomers http://www.julianhaller.de/Dissertation_e.htm