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What do silk,

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DNA,

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wood,

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balloons,

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and Silly Putty all have in common?

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They're polymers.

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Polymers are such a big part of our lives

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that it's virtually impossible

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to imagine a world without them,

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but what the heck are they?

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Polymers are large molecules

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made of small units called monomers

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linked together like the railroad cars from a train.

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Poly means many,

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and mono means one,

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and mers or mero means parts.

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Many polymers are made by repeating

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the same small monomer over and over again

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while others are made from two monomers

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linked in a pattern.

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All living things are made of polymers.

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Some of the organic molecules in organisms

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are small and simple,

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having only one of a few functional groups.

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Others, especially those that play structural roles

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or store genetic information,

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are macromolecules.

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In many cases, these macromolecules are polymers.

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For example, complex carbohydrates

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are polymers of simple sugars,

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proteins are polymers of amino acids,

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and nucleic acids, DNA and RNA,

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which contain our genetic information,

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are polymers of nucleotides.

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Trees and plants are made

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of the polymer cellulose.

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It's the tough stuff you find in bark and stems.

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Feathers,

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fur,

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hair,

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and fingernails

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are made up of the protein keratin,

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also a polymer.

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It doesn't stop there.

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Did you know that the exoskeletons

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of the largest phylum in the animal kingdom,

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the arthropods,

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are made of the polymer chitin?

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Polymers also form the basis

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for synthetic fibers, rubbers, and plastics.

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All synthetic polymers are derived from petroleum oil

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and manufactured through chemical reactions.

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The two most common types of reactions

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used to make polymers

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are addition reactions

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and condensation reactions.

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In addition reactions,

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monomers simply add together to form the polymer.

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The process starts with a free radical,

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a species with an unpaired electron.

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The free radical attacks

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and breaks the bonds to form new bonds.

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This process repeats over and over

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to create a long-chained polymer.

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In condensation reactions,

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a small molecule, such as water,

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is produced with each chain-extending reaction.

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The first synthetic polymers

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were created by accident

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as by-products of various chemical reactions.

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Thinking they were useless,

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chemists mostly discarded them.

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Finally, one named Leo Baekeland

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decided maybe his useless by-product

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wasn't so useless after all.

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His work resulted in a plastic

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that could be permanently squished into a shape

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using pressure and high temperatures.

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Since the name of this plastic,

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polyoxybenzylmethylenglycolanhydride,

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wasn't very catchy,

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advertisers called it Bakelite.

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Bakelite was made into telephones,

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children's toys,

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and insulators for electrical devices.

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With its development in 1907,

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the plastics industry exploded.

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One other familiar polymer, Silly Putty,

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was also invented by accident.

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During World War II,

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the United States was in desperate need

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of synthetic rubber to support the military.

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A team of chemists at General Electric

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attempted to create one

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but ended up with a gooey, soft putty.

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It wasn't a good rubber substitute,

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but it did have one strange quality:

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it appeared to be extremely bouncy.

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Silly Putty was born!

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Synthetic polymers have changed the world.

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Think about it.

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Could you imagine getting through a single day

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without using plastic?

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But polymers aren't all good.

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Styrofoam, for example, is made mainly of styrene,

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which has been identified as a possible carcinogen

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by the Environmental Protection Agency.

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As Styrofoam products are being made,

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or as they slowly deteriorate in landfills or the ocean,

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they can release toxic styrene

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into the environment.

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In addition, plastics that are created

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by addition polymerization reactions,

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like Styrofoam,

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plastic bags,

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and PVC,

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are built to be durable and food-safe,

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but that means that they don't break down

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in the environment.

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Millions of tons of plastics

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are dumped into landfills every year.

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This plastic doesn't biodegrade,

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it just breaks down

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into smaller and smaller pieces,

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affecting marine life

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and eventually making their way back to humans.

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Polymers can be soft or hard,

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squishy or solid,

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fragile or strong.

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The huge variation between

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means they can form

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an incredibly diverse array of substances,

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from DNA

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to nylon stockings.

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Polymers are so useful

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that we've grown to depend on them every day.

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But some are littering

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our oceans, cities, and waterways

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with effects on our health

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that we're only beginning to understand.