Polymer, << POL ih muhr, >> is a large molecule formed by the chemical linking of many smaller molecules into a long chain. The small molecular building units are called monomers. Monomers are joined into chains by a process of repeated linking known as polymerization. A polymer may consist of thousands of monomers. Some polymers occur naturally. Others are synthetic.
Many common and useful substances are polymers. For example, starch and wool are naturally occurring polymers. Starch is formed by plants from a simple sugar called glucose, and wool is a variety of protein. Nylon and polyethylene, a tough plastic material, are examples of synthetic polymers. Rubber, another polymer, occurs naturally and is also made synthetically.
A chain molecule has a definite length, but, like a piece of string, it can assume a variety of shapes. This combination of molecular length and flexibility gives polymers many useful and unique properties. For example, rubber and numerous other polymers can be stretched to several times their normal length without breaking. The chains simply straighten into more extended shapes. Because of the large size of the molecules, polymers do not dissolve easily. They also have high viscosity (resistance to flowing).
