The chemical process of bonding these small units together is called polymerization. To form a chain, a monomer must have at least two reactive binding sites. These sites are often double bonds between carbon atoms or specific functional groups.
Functional groups are clusters of atoms that easily react with other molecules. Some monomers join through addition reactions where double bonds break open to connect. This process links the units together without creating any extra chemical byproducts.
Other monomers link through condensation reactions by sharing functional groups. During this reaction, the molecules release a small byproduct like water or hydrochloric acid. A common student misconception is that monomers must all be identical to form a polymer.
In fact, chemists often mix different monomers to create custom materials called copolymers. Vinyl chloride is a synthetic monomer that contains a chlorine atom. It polymerizes to form polyvinyl chloride, which is a common plastic used in pipes.
Nature also uses monomers to build essential life molecules like proteins and DNA. For example, amino acids are the monomers that link together to make proteins. Nucleotides are the monomers that form the long strands of DNA. Synthetic monomers are manufactured from crude oil to make plastics, fibers, and synthetic rubbers.