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Polyox

When polyox (polyethylene oxide) mixes with water, its oxygen atoms can attach to hydrogen atoms in the water, setting up lots of chains in many directions.

This chain structure is called a polymer

Because polyethylene oxide has a lot of oxygen atoms on the chain, there are lots of opportunities for binding. The resulting gel is very thick because its molecules like to stick together, a process called cohesion. Strong cohesion properties can also impact how a fluid flows and in fact, polyox does not flow like other liquids.

Polyox is self-siphoning; once you start pouring it from one cup to another, it will continue the process even if you tilt the first cup back up. This video explains this phenomenom nicely using a long chain of beads to illustrate the polymer structure of polyox. 

Polyox is also a non-Newtonian fluid which becomes thinner when stressed unlike Ooblek which thickens under stress. 

Objectives

  • Investigate the properties of a self-siphoning fluid.

  • Describe the structure of polymers

Materials

  • Per Demo or Class:
    two 600 mL beakers
    polyethylene oxide (polyox) *
    scale to measure 3 to 4 grams of polyox
    alcohol
    corn syrup
    eggbeater or mixer

    * Can be found at Teacher Source or online as Poly-Ox or Siphoning Gel.

Key Questions

  • How does the poly-ox gel behave differently from the corn syrup?
  • If the beaters were in a powder would the powder climb the beaters or move away?
  • What if the beaters were in a bowl of long threads?

What To Do

Before demonstration:

  1. Pour 3 to 4 grams of polyox powder into a 600 mL beaker.
  2. Add 25 mL of alcohol and swirl until the powder is completely wet.
  3. Add 350 to 400 mL of water in one pour. Stir vigorously until it gels completely.

During demonstration:

  1. Take the unused 600 mL beaker and fill half-full with corn syrup.
  2. On the first speed setting, beat the corn syrup using the mixer. Ask students about any observations they can make about what is happening with the corn syrup. (The corn syrup is thrown away from the beaters).
  3. Now use the mixer with the polyox gel. Ask students to predict what could happen. (The gel will climb the beaters. Soon the whole gel mass is on the beaters)

Extensions

  • Try pouring polyox gel from one cup to another. The goop will lift itself out of the top cup to flow down into the bottom one. Polyox is a shear thinning non-Newtonian fluid (like ketchup), this means in a bottle it won't flow out easily unless shaken, squeezed, or smacked. Give it a go!