Fun with Polymers!

Do you like goop, or putty? Did you check out the pink goop at the ice cream social? Fun stuff to play with right? Here’s how you can make some of your own.
Materials:
2 paper cups
4 tablespoons white wood glue, such as Elmer’s
Warm water
Food coloring (optional)
1 tablespoon and 2 teaspoons borax powder (found in laundry section at the store)
1 tablespoon cornstarch
Procedure:
1. In a paper cup, mix the glue, 4 tablespoons water, and a few drops of food coloring. Add 1 tablespoon borax and the cornstarch and mix well.
2. In another cup, mix 2/3 cup water and 2 teaspoons borax until the borax dissolves. Pour 2 tablespoons of the borax and water solution into the glue mixture and stir until it’s stiff.
3. Let the mixture set for a minute, then take it out of the cup and rinse with water. Blot the extra water with a paper towel and knead the mixture until it’s smooth. If you want it to be stiffer, add more of the borax and water solution.
What does your goop do? Try bouncing it, breaking it, stretching it. Does it keep its shape? Is it hard, soft or both?

Polymer is a funny word. A polymer is a chemical made up of many repeated parts (poly=many; mer=unit). The glue contains a polymer, polyvinyl acetate (PVA), which is made from many monomers (individual chemicals) of vinyl acetate. So the glue is a polymer to start with but when the borax is added, the chains cross-link to make even bigger—and stiffer—polymer chains. Cross links are like chemical bridges between polymer chains, linking them together. Knowing this what do you think would happen when you vary the amount of borax you add? Try it!