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A young student is studying a model of molecules.
Image credit: Hero Images/Getty ImagesTo grasp the concept of a monomer, imagine a set of colorful beads meant for a small child, designed to fit together. Each bead stands alone, but when connected with another, they form a completely new structure.
The word monomer is derived from the Greek terms mono, meaning "one," and meros, which translates to "part." Combined, these words create the phrase "one part," which describes a monomer: a single molecule that can join with others to form a larger compound. A well-known natural monomer is glucose, which often bonds with other molecules to create starch and glycogen.
Similar to how the beads fit together, monomers must align correctly to bond. This process takes place through a chemical reaction known as polymerization, where two molecules connect by sharing pairs of electrons, forming covalent bonds [source: Larsen]. These monomers may be identical or different types.
When multiple monomer molecules bond together, they form a polymer, a structure made up of many repeating monomer units linked in a long chain [source: Larsen]. This bonding ability, which allows monomers to connect with at least two other monomer molecules, is known as polyfunctionality [source: Brittanica]. The number of molecules a monomer can bond with depends on how many active sites are present on the molecule to form covalent bonds – much like how you can only hold hands with two other people at a time.
The type of structure that results from these bonds is determined by how many other molecules a monomer can link to. If a monomer is able to bond with only two other molecules, the polymer takes on a chain-like form. But when a monomer can bond with three or more molecules, the resulting polymer forms a three-dimensional, cross-linked structure [source: Innovate Us].
Most monomers are organic in nature [source: Brittanica]. Amino acids, for example, are natural monomers that can polymerize into proteins. Nucleotides, found in the cell nucleus, combine to form DNA and RNA. On the other hand, some monomers are synthetic, like vinyl chloride, a common man-made monomer. Through polymerization, vinyl chloride molecules form polyvinyl chloride (PVC), one of the oldest and most widely used synthetic plastics. PVC is found in everything from building materials to bottles, toys, and even fashion products [sources: Innovate Us, PVC].
Next time you pick up a plastic water bottle, think about that solitary bead waiting to be threaded onto a string. Just like that bead, monomers bonded together to create the plastic polymer that forms the bottle in your hand.
