Skip to main content Skip to Search Box

Definition: polymer from Dictionary of Energy

Materials. 1. a large molecule (macromolecule) formed by the union of simpler units that are identical to each other (monomers); it may be natural, such as cellulose or DNA, or synthetic, such as nylon or polyethylene; polymers usually contain many more than five monomers, and some may contain hundreds or thousands of monomers in each chain. 2. an industrial material or product composed of such molecules.


Summary Article: polymer
from The Columbia Encyclopedia

(pŏl'ӘmӘr), chemical compound with high molecular weight consisting of a number of structural units linked together by covalent bonds (see chemical bond). The simple molecules that may become structural units are themselves called monomers; two monomers combine to form a dimer, and three monomers, a trimer. A structural unit is a group having two or more bonding sites. A bonding site may be created by the loss of an atom or group, such as H or OH, or by the breaking up of a double or triple bond, as when ethylene, H2C=CH2, is converted into a structural unit for polyethylene, –H2C–CH2–. In a linear polymer, the structural units are connected in a chain arrangement and thus need only be bifunctional, i.e., have two bonding sites. When the structural unit is trifunctional (has three bonding sites), a nonlinear, or branched, polymer results. Ethylene, styrene, and ethylene glycol are examples of bifunctional monomers, while glycerin and divinyl benzene are both polyfunctional. Polymers containing a single repeating unit, such as polyethylene, are called homopolymers. Polymers containing two or more different structural units, such as phenol-formaldehyde, are called copolymers. All polymers can be classified as either addition polymers or condensation polymers. An addition polymer is one in which the molecular formula of the repeating structural unit is identical to that of the monomer, e.g., polyethylene and polystyrene. A condensation polymer is one in which the repeating structural unit contains fewer atoms than that of the monomer or monomers because of the splitting off of water or some other substance, e.g., polyesters and polycarbonates. Many polymers occur in nature, such as silk, cellulose, natural rubber, and proteins. In addition, a large number of polymers have been synthesized in the laboratory, leading to such commercially important products as plastics, synthetic fibers, and synthetic rubber. Polymerization, the chemical process of forming polymers from their component monomers, is often a complex process that may be initiated or sustained by heat, pressure, or the presence of one or more catalysts.

The Columbia Encyclopedia, © Columbia University Press 2018

Related Articles


Full text Article polymer
The Encyclopedia of Ecology and Environmental Management, Blackwell Science

The product of a polymerization reaction, i.e. a chemical reaction in which two or more (usually many) identical molecules join together to...

Full text Article polymer
Philip's Encyclopedia

Substance formed by the union of from two to several thousand simple molecules (monomers) to form a large molecular structure. Some, such as ...

Full text Article Polymer
Dictionary of Environmental Science and Technology

A chemical compound made by the repeated joining of monomer molecules. (⇒ polymerization ) ...

See more from Credo