From DNA to Silly Putty: The diverse world of polymers - Jan Mattingly

What do silk,

DNA,

wood,

balloons,

and Silly Putty all have in common?

They're polymers.

Polymers are such a big part of our lives

that it's virtually impossible

to imagine a world without them,

but what the heck are they?

Polymers are large molecules

made of small units called monomers

linked together like the railroad cars from a train.

Poly means many,

and mono means one,

and mers or mero means parts.

Many polymers are made by repeating

the same small monomer over and over again

while others are made from two monomers

linked in a pattern.

All living things are made of polymers.

Some of the organic molecules in organisms

are small and simple,

having only one of a few functional groups.

Others, especially those that play structural roles

or store genetic information,

are macromolecules.

In many cases, these macromolecules are polymers.

For example, complex carbohydrates

are polymers of simple sugars,

proteins are polymers of amino acids,

and nucleic acids, DNA and RNA,

which contain our genetic information,

are polymers of nucleotides.

Trees and plants are made

of the polymer cellulose.

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

Feathers,

fur,

hair,

and fingernails

are made up of the protein keratin,

also a polymer.

It doesn't stop there.

Did you know that the exoskeletons

of the largest phylum in the animal kingdom,

the arthropods,

are made of the polymer chitin?

Polymers also form the basis

for synthetic fibers, rubbers, and plastics.

All synthetic polymers are derived from petroleum oil

and manufactured through chemical reactions.

The two most common types of reactions

used to make polymers

are addition reactions

and condensation reactions.

In addition reactions,

monomers simply add together to form the polymer.

The process starts with a free radical,

a species with an unpaired electron.

The free radical attacks

and breaks the bonds to form new bonds.

This process repeats over and over

to create a long-chained polymer.

In condensation reactions,

a small molecule, such as water,

is produced with each chain-extending reaction.

The first synthetic polymers

were created by accident

as by-products of various chemical reactions.

Thinking they were useless,

chemists mostly discarded them.

Finally, one named Leo Baekeland

decided maybe his useless by-product

wasn't so useless after all.

His work resulted in a plastic

that could be permanently squished into a shape

using pressure and high temperatures.

Since the name of this plastic,

polyoxybenzylmethylenglycolanhydride,

wasn't very catchy,

advertisers called it Bakelite.

Bakelite was made into telephones,

children's toys,

and insulators for electrical devices.

With its development in 1907,

the plastics industry exploded.

One other familiar polymer, Silly Putty,

was also invented by accident.

During World War II,

the United States was in desperate need

of synthetic rubber to support the military.

A team of chemists at General Electric

attempted to create one

but ended up with a gooey, soft putty.

It wasn't a good rubber substitute,

but it did have one strange quality:

it appeared to be extremely bouncy.

Silly Putty was born!

Synthetic polymers have changed the world.

Think about it.

Could you imagine getting through a single day

without using plastic?

But polymers aren't all good.

Styrofoam, for example, is made mainly of styrene,

which has been identified as a possible carcinogen

by the Environmental Protection Agency.

As Styrofoam products are being made,

or as they slowly deteriorate in landfills or the ocean,

they can release toxic styrene

into the environment.

In addition, plastics that are created

by addition polymerization reactions,

like Styrofoam,

plastic bags,

and PVC,

are built to be durable and food-safe,

but that means that they don't break down

in the environment.

Millions of tons of plastics

are dumped into landfills every year.

This plastic doesn't biodegrade,

it just breaks down

into smaller and smaller pieces,

affecting marine life

and eventually making their way back to humans.

Polymers can be soft or hard,

squishy or solid,

fragile or strong.

The huge variation between

means they can form

an incredibly diverse array of substances,

from DNA

to nylon stockings.

Polymers are so useful

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

But some are littering

our oceans, cities, and waterways

with effects on our health

that we're only beginning to understand.