What is soft matter

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Revision as of 21:39, 17 September 2008 by Nsinha (Talk | contribs) (Soft matter - Ice cream!)

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Structured and fluid

  • Things that don’t hurt your hand when you hit them.
  • Synonymous with “complex fluids”
  • Examples: hair gel, mayonnaise, shaving cream, colloidal crystals, polymer solutions and blends


Macosko Fig 5-3-3.gif Homberg Fig 2-1.gif Weitz 339-60-1989.png
Macosko Fig. 5-3-3 Homberg Fig. 2.1 Weitz Nature 339,60,1989.

Comments on Figures: Elaborate HERE!





Properties of soft matter

  • Viscoelasticity
  • Turbidity/opacity
  • Irreversible fragility
  • Temperature sensitivity


Indian boot - de Gennes 1996.gif 2500 years ago, South American Indians take sap from a hevea tree, cover their feet, wait about 20 minutes, and a pair of boots is created. The latex is crosslinked by oxidation only, so is weak. In 1830 Charles Goodyear decides to boil the hevea latex with sulfur (heaven only knows why), the crosslinking is much, much better, and eventually the radial tire is created. (de Gennes, 1996, p.4)





Ink making for soft matter physicists

Soot - de Gennes 1996.gif Poor dispersion - de Gennes 1996.gif Good dispersion - de Gennes 1996.gif
de Gennes, 1996, p.29

If you think this is primitive, check out how newpaper ink is make.





Soft matter - Ice cream!

Plain frozen cream is as hard as rock, but the micro-scale structure of ice cream turns it into a wonderful dessert. Ice cream is a three phase mixture of pure water crystals, concentrated cream and sugar, and air pockets. The cream solution can remain liquid, since the sugar lowers the freezing point below 0 C. It coats each of the millions of ice crystals and lightly binds them together. The texture of ice cream is further improved by air pockets introduced during mixing. These air pockets are stabilized by fat molecules from the cream. The air weakens the network of crystals and cream, making the ice cream easier to serve and to eat. Several variations of ice cream have evolved over the centuries. American ice cream traditionally uses a combination of milk and cream, whereas French ice cream uses lower-fat milk, with egg yolks as a stabilizer. Italian gelato also uses egg yolks, but contains less air, resulting in a denser product. Low-fat ice cream utilizes additives such as corn syrup, powdered milk, and vegetable gums. Indian kulfi is based on a recipe from the 16th century, in which milk is boiled down to concentrate the proteins and sugar, then frozen without stirring.
Ice cream - Hamley.gif TEM of a typial ice-cream. (a) Ice crystals, average size 50 nm, (b) air cells, average size 100-200 mm, (c) unfrozen material. (W.S. Arbuckle, Ice Cream, 2nd ed., Avi Publishing, 1972. also, Hamley, Fig. 3.20)
For more information about ice cream, see On Food and Cooking, 2nd ed., Scribner, 2004. by Harold McGee (pp. 39-45), from which this section is based.




From great biology to great physics

Connect these scientists:

  • Thomas Graham (1805-1869)
  • Robert Brown (1773-1858)
  • Michael Faraday (1791-1867)
  • Ludwig Boltzmann (1844-1906)
  • Albert Einstein (1897-1955)
  • Jean Perrin (1870-1942)

Hint: Size dependence of diffusion





Length scales and order

Polymers in solution.png Surfactants in solution.png Particles in dispersion.png
Polymers in solution Surfactant solutions Particle dispersions

Comments:




De Gennes 1997 p 29.gif De Gennes 1997 Fig 1-1.gif De Gennes 1997 Fig III-3.gif
Structure and size, de Gennes, 1997, p.29 Motion and size, de Gennes,1997, Fig I-1 Structure and concentration, de Gennes, 1993, Fig. III-1
Fractals Random walk eqn.png Polymer cStar eqn.png

Comments:





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