Micellar Water

Once upon a time you would buy a bar of soap and use it to wash your hands, face, body, and possibly even your hair.
Not today! Now you have hand-wash for your hands, body-wash for your body, shampoo for your hair, and a huge range of different products to clean your face including "micellar water" or "micellar cleansing water".
Unlike other face-cleaning products which need to be washed off with water, the makers of "micellar water" claim that it will cleanse your skin without vigorous rubbing or rinsing.
Intriguing! This "micellar water" sounds like some kind of magic doesn't it?
What's in "micellar water" and how does it work?

Read all about it in the September 2019 edition of AUS-e-NEWS, AUS-e-TUTE's free quarterly newsletter for chemistry students and teachers.

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DOSS and Oil Spills

The molecular formula for dioctyl sodium sulfosuccinate, DOSS, is shown on the right. This is the anionic detergent molecule that was used to disperse the oil from the Deepwater Horizon spill in the Gulf of Mexico in 2010. When applied to an oil spill, DOSS decreases the size of oil droplete and prevents large oil slicks from forming.
BP applied about 1.84 million gallons of DOSS to the 210 million gallons of oil that is estimated to have gushed out of the oil well.
At the time it was believed that DOSS degraded rapidly in the environment so that it would not harm the marine environment.

Recent studies, however,  have shown that DOSS persists in the environment for much longer than was previously thought. Four years after the Gulf oil spill, DOSS remains present in deep-sea sediments and corals and in sand patties on Gulf beaches. mean for marine life or for the people who frequent the beaches? Scientists do not yet know what this might mean for marine life or for the people who frequent the beaches so some Gulf beaches have signs to warn people not to touch the sand patties.

Reference:
Helen K. White, Shelby L. Lyons, Sarah J. Harrison, David M. Findley, Yina Liu, Elizabeth B. Kujawinski. Long-Term Persistence of Dispersants following the Deepwater Horizon Oil Spill. Environmental Science & Technology Letters, 2014; 1 (7): 295 DOI: 10.1021/ez500168r

Further Reading:
http://www.ausetute.com.au/members/detergent.html (detergent tutorial for members)
http://www.ausetute.com.au/members/soaps.html (soaps tutorial for members)
http://www.ausetute.com.au/members/molecularformula.html (molecular formula tutorial for members)
http://www.ausetute.com.au/members/structural2D.html  (2-dimensional structural formula tutorial for members)
http://www.ausetute.com.au/members/condensedsf.html (Condensed structural formula tutorial for members)
http://www.ausetute.com.au/members/skeletal.html (Skeletal formula tutorial for members) 

Suggested Study Questions:

1.  Explain why dioctyl sodium sulfosuccinate, DOSS, is an anionic detergent molecule.
2. Give the name for the type of formula shown for dioctyl sodium sulfosuccinate, DOSS, in the article
3. Identify the functional groups found on a dioctyl sodium sulfosuccinate, DOSS, molecule.
4. Identify areas of the dioctyl sodium sulfosuccinate, DOSS, molecule that are:
   • hydrophilic
   • hydrophobic
5. Explain how the dioctyl sodium sulfosuccinate, DOSS, molecule might dissolve in water.
6. Explain how the dioctyl sodium sulfosuccinate, DOSS, molecule might dissolve in oil.
7. Explain how dioctyl sodium sulfosuccinate, DOSS, molecules might help break an oil spoil up into smaller oil droplets.
8. Write a complete 2-dimensional structural formula for dioctyl sodium sulfosuccinate, DOSS.
9. Write a condensed structural formula for dioctyl sodium sulfosuccinate, DOSS.
10. Write the molecular formula for dioctyl sodium sulfosuccinate, DOSS.

Stable Foam

Foams often have detergent properties due to their particular texture and the molecules that make up the foam. These molecules, which must be dispersed in water to create foam, are called "surface-active." They are located spontaneously in water and air, so that very thin films of water can stabilize around air bubbles of foam with a special architecture. Due to such properties, various foams have numerous applications in cleaning, decontamination, cosmetics, battling pollution and Scientists have been studying a particular surface-active molecule known as 12-hydroxystearic acid which is produced from castor oil.

This molecule is insoluble in water but it becomes water soluble when a suitable salt is added. This surfactant is very special because even in small quantities, it produces abundant foam and, above all, remains stable for more than six months, in contrast with traditional surfactants that stabilize foams for only several hours.

At temperatures between 20 and 60°C, the surfactant disperses in water in the form of tubes that are several microns in size. The tubes form a structure that is perfectly stable and rigid in very thin films of water located between air bubbles, which explains the foam's resistance.
Above 60°C, the tubes merge into micelles, spherical assemblies that are a thousand times smaller (several nanometers). The previously stable foam then collapses because the rigid structure disappears. The researchers have demonstrated that this transition from an assembly of tubes to an assembly of micelles is reversible. If the foam's temperature is increased, its volume will diminish when micelles start to form, and if the temperature is again reduced to between 20 and 60°C, the tubes will form again and the form will re-stabilize (to regain the initial volume of the foam, air must be re-injected).

Reference
Anne-Laure Fameau, Arnaud Saint-Jalmes, Fabrice Cousin, Bérénice Houinsou Houssou, Bruno Novales, Laurence Navailles, Frédéric Nallet, Cédric Gaillard, François Boué, Jean-Paul Douliez. Smart Foams: Switching Reversibly between Ultrastable and Unstable Foams. Angewandte Chemie, 2011; DOI: 10.1002/ange.201102115

Further Reading
Synthetic Detergents
Soaps and Saponification
Functional Groups
Lipids

Suggested Questions:

1. Give the molecular formula for 12-hydroxystearic acid.
2. On the structural formula of 12-hydroxystearic acid identify the:
   • carboxyl functional group
   • hydroxyl functional group
3. Is 12-hydroxystearic acid a saturated or unsaturated fatty acid. Explain your answer.
4. Draw 2 structural isomers of 12-hydroxystearic acid.
5. Explain why 12-hydroxystearic acid is not very soluble in water.
6. Draw a structural formula for lithium 12-hydroxystearate, the lithium salt of 12-hydroxystearic acid.
7. What properties of lithium 12-hydroxystearate make it a common component in greases used in motor vehicles, aircraft and heavy machinery?
8. Explain how the properties listed above in question 7 relate to the chemical structure of lithium 12-hydroxystearate.
9. Design experiments to test:
   
   • the stability of the foams formed by a range of household detergents
   • the stability of foam at different temperatures
   • the stability of foam in the presence of different salts
     
   
   

Cardanol

Chemists at The City College of New York have designed a molecule which has both water-adhering and water-repelling ends, from cardanol (the structure on the right), a naturally available material found in cashew nutshell liquid.

When mixed with water, the designer molecules formed a self-assembled structure called a micelle with a water-adhering exterior and water-repelling interior.

At 50^oC the micelles take on a 3-dimensional structure known as a vesicle that is about 200 times larger and more viscous. The molecules stick together enough to be draw out into a thin strand, just like glue.

Cooling the material allows the molecules to revert to their original micellar structure.

Heating causes the micelles to re-arrange themselves into an interlocking bi-layer which undergoes curvature. The structure is stabilized in part by the hydrogen bonding.

Reference
Vijai S. Balachandran, Swapnil R. Jadhav, Padmanava Pradhan, Sacha De Carlo, George John. Adhesive Vesicles through Adaptive Response of a Biobased Surfactant. Angewandte Chemie International Edition, 2010; DOI: 10.1002/anie.201005439

Further Reading
Detergents
Soaps and Saponification
Functional Groups
Percentage Composition
Intermolecular Forces
Intramolecular Forces

Study Questions

1. Identify the functional groups present in a molecule of cardanol.
2. Give the molecular formula for cardanol.
3. Calculate the percentage of carbon, hydrogen and oxygen present in a mole of cardanol.
4. On the molecular structure of cardanol, identify the water-adhering area and the water-repelling area.
5. What is the name given to a molecule that adheres to water?
6. What name is given to a molecule the repels water?
7. Draw a diagram to show how cardanol molecules could form a micelle.
8. Given the description of the behaviour of the designer molecule in the article above, in what ways do you think it differs from the structure of cardanol?