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Monomer

physical science Maturity 11-13 Next article →

A monomer is a fundamental building block of chemistry. The name comes from the Greek word "mono," meaning one, and "mer," meaning part. These single molecules are capable of reacting with other monomers. This reaction creates much larger structures called polymers. Polymers can take many shapes. They might form long, thin chains. They can also form two-dimensional or three-dimensional networks. This entire process of joining molecules together is known as polymerization. Understanding monomers is essential for understanding how both nature and industry build complex materials.

Condensation polymerization diacid diamine
Condensation polymerization diacid diamine

Polymerization happens through different chemical mechanisms. One major method is called addition polymerization. In this process, monomers simply link together to form a chain. Another method is called condensation polymerization. This process is more complex because it often involves a change in the ratio of the parts. In many condensation reactions, a small molecule like water is released as a byproduct. For example, creating nylon requires a specific type of condensation polymerization. This process uses two different monomers to create the polymer chain.

Chemists classify monomers in several different ways. They can be grouped by whether they are natural or synthetic. They can also be classified by their physical properties. Some monomers are polar, while others are nonpolar. Some have a cyclic shape, which means they form a ring. Others are linear, meaning they are shaped like a straight line. Scientists also group them by the type of polymer they produce. This includes whether they participate in addition or condensation polymerization. These classifications help researchers predict how a material will behave.

Condensation polymerization diacid diamine
Condensation polymerization diacid diamine

We can also categorize polymers by the variety of monomers they contain. A polymer made from only one kind of monomer is called a homopolymer. However, many polymers are copolymers. Copolymers are created using two or more different types of monomers. The ratio of these monomers varies depending on the process. In condensation polymerization, the ratio is often 1:1. For instance, making many types of nylon requires equal amounts of a diamine and a dicarboxylic acid. In addition polymerization, the second monomer might only make up a few percent of the total. A small amount of 1-octene can be added to ethylene to create specialized polyethylene.

Condensation polymerization diacid diamine
Condensation polymerization diacid diamine

Synthetic monomers are man-made molecules used to create many common plastics. Ethylene gas is a very important monomer used to make polyethylene. By modifying ethylene, scientists create other materials. Tetrafluoroethylene is used to make Teflon. Vinyl chloride is the monomer used for PVC. Styrene is another common monomer used to produce polystyrene. Other specialized monomers include BPA, which is a precursor for polycarbonate. Dimethylsilicon dichloride is used to create polydimethylsiloxane after it undergoes hydrolysis. Even the plastic used for artificial nail extensions comes from a specific acrylic monomer called ethyl methacrylate.

Condensation polymerization diacid diamine
Condensation polymerization diacid diamine

Nature relies on monomers to build the very foundations of life. These are often called biopolymers. Amino acids are the monomers that build proteins. There are usually about 20 different types of amino acid monomers used in this process. Because they use many different types, proteins are not homopolymers. This polymerization occurs at structures called ribosomes. Another vital group is nucleotides. These are the monomers for polynucleic acids like DNA and RNA. Each nucleotide consists of a phosphate group, a nitrogenous base, and a pentose sugar. Four types of nucleotide monomers serve as precursors for DNA, while four different types build RNA. These are found within the cell nucleus.

Condensation polymerization diacid diamine
Condensation polymerization diacid diamine

Other natural monomers are found in plants and common substances. Glucose is one of the most abundant natural monomers in the world. It is a monosaccharide that links together through glycosidic bonds. These links create large polymers like starch, cellulose, and glycogen. Another important natural monomer is isoprene. When isoprene polymerizes, it forms natural rubber. This can result in cis-1,4-polyisoprene or trans-1,4-polymer. Many synthetic rubbers are also based on butadiene, which is structurally related to isoprene. From the DNA in your cells to the plastic in a container, monomers are the tiny units that make the large world possible.

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File:Condensation polymerization diacid diamine.svg
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