Polymers are large molecules called macromolecules consisting of numerous repeating structural units called monomers having different functional groups. A monomer is a small molecule that can be combined to form a polymer through a reaction. These reactions come in two main varieties, including chain-reaction polymerization and step-reaction polymerization. Chain-reaction polymerization is also known as Addition, while step-reactions are often called Condensation.
The carbon atoms of the polymer backbone or chain are attached to the monomers in an organic polymer. A polymer may also be inorganic, in which case, in place of carbon atoms, there may be atoms such as silicon.
A biological macromolecule is present in living organisms. This contains molecules such as carbohydrates, proteins, nucleic acids, and lipids. They are essential for the survival of all known life forms. The temperature dependence of the process of polymerization is very different from that of standard inorganic reactions. At low temperatures, there is no polymerization and at high temperatures polymerization occurs.
There are three basic steps during which free radicals and monomers combine to form polymers, including initiation, propagation, and termination.
- Disaccharides and polysaccharides like maltose, sucrose, and glycogen
- All proteins made from amino acids
- Nucleic acids, like DNA and RNA, made from nucleotides
Examples of commercial condensation polymers are:
- Polyethylene terephthalate (a polyester)
- Nylon 6,6