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Polymer Modeling Activity

   
 

In this activity, you will use paper clips to make models of different types of polymers.

Take your eyes off of this page and look around you. What do you see that is made of synthetic polymers? Many things found in our environment are made of synthetic polymers. Here is a short list of examples:

  • sunglasses * tooth brush * super glue * paint brush * motorcycle helmet * tennis shoes * Frisbee * 2-liter soda bottles * disposable razors * Honda CRX * Astroturf * photographs * street signs * pens * hairspray * automobile paint * video tapes * rubber bands * balloons * bicycle tires * umbrella * guitar strings * carpet * shower doors * hearing aids * Scotch Tape * fishing lines * trash bags * toilet seats
  • Despite the variety of products, there are just three basic polymer structures: (1) linear, (2) branched, and (3) cross-linked polymers. Notice how the names give you clues about what the polymer chains look like. How do you think the structures differ from each other?

    Materials: Before you begin to make these three different types of polymer structures, you need to gather a large collection of paper clips (20 or more).

  • Action: Microwaveable food containers, Dacron carpets and Kevlar ropes are examples of products made with linear polymers.
  • To make a model of a linear polymer, connect some paper clips together, end-to-end in a straight chain, like this:
         

    Each paper clip represents a monomer, and the chain of paper clips is a model for a polymer. You can attach as many paper clips together as you want, because theoretically the number of monomer units that join to make a polymer chain is infinite. In reality, the number of monomer units in a polymer commonly ranges from 1,000 to 10,000 or more. (This corresponds to typical molecular weights of 14,000 to 500,000 grams per mole.)


    Soft, flexible shampoo bottles and milk jugs are examples of products generally made using branched polymers. To find some other examples, look on food containers and other plastics for the LDPE (low-density polyethylene) mark. To make a model of a branched polymer, connect some paper clips end-to-end exactly as you did to make a straight-chain polymer. Then, attach a couple of paper clips to any of the paper clips that are not at the ends of the long chain, so that it looks something like this:

         

    When a sample of the polymer polyethylene is magnified 15,000 times, you can see the branch-like fibers.

         


    Car tires and bowling balls are two examples of products composed of cross-linked polymers. To make a model of a cross-linked polymer, make several (at least three) branched chains just like you did above, and lay them out next to each other. Then, connect some of the paper-clip branches from one chain to the branches of another chain. You can repeat this with as many branches and chains as you have, until they are all linked together. Your finished cross-linked polymer may look something like this:

         


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