From trees to tires, from lunch to grocery bags, from breakfast cereal to school clothes: Polymers play an essential role in the human and natural world. As people become more environmentally aware, many are looking for ways to replace artificially created items with more sustainable substitutes. Polymers are no exception.

Polymers are long molecules made from monomers. "Poly" means many, and "mono" means one or single. "Mers" means parts. Polymers therefore means many parts, and polymers are made of many monomers or single parts. Different polymers form from different monomers. Also, when the arrangement of monomers changes, a different polymer may form.

Monomers connect in two different ways. In the first, the monomers connect directly, like building blocks linked together. These are called addition polymers. Many synthetic monomers form addition polymers. In the second kind of connection, the monomers release a water molecule when they link together. These are called condensation polymers. Most natural polymers are condensation polymers, so water is a natural byproduct of the linking monomers.

The millions of different kinds of protein polymers are all made from amino acid monomers. Although there are only 20 different kinds of amino acids, the many different combinations and arrangements result in a great variety of proteins. Some different types of protein polymers include:

• skin
  
• body organs
  
• muscles
  
• hair
  
• fingernails
  
• feathers
  
• hooves
  
• fur

A wide range of animal fibers, from wool to silk, come from protein polymers. Spider silk, one of the strongest fibers known, is a protein polymer. Leather, made from animal skin, results from protein polymers.

Advantages of synthetic or artificial polymers include stability and consistency of the product. Synthetic rubber, for example, doesn't rot like natural rubber will. Synthetic rubber can also be customized for different purposes. Synthetic polymer examples include:

• nylon
  
• epoxies
  
• polyethylene
  
• Plexiglas
  
• Styrofoam
  
• Kevlar^®
  
• Teflon^®

From plastic containers to furniture to clothes to spray foam polymers, synthetic polymers permeate modern life.