| 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:
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).
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:
Web author: Tug Sezen
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