Name: polymer chains and how they form
Uploaded: 2020-09-24T15:06:53.000Z
Duration: 2 min 34 s
Channel: JoVE

A polymer is a chain of small molecules, called monomers, that are held together by covalent bonds. Organisms can synthesize biological polymers, or scientists can synthesize polymers in the laboratory.
Natural polymers include DNA, the genetic material found in all living organisms, and proteins, polysaccharides, and lipids, the building blocks of life.
Plastics are some of the most common synthetic polymers and include nylon, polyethylene, and teflon.
The process of monomers linking to each other to form a larger molecule is known as polymerization. Monomers polymerize by two distinct reaction mechanisms, condensation and addition.
Condensation polymerization is when two monomers with a reactive hydrogen atom and hydroxyl group, respectively, link to each other, with the release of water as a by-product. Most natural polymers are formed through condensation reactions.
In addition polymerization, monomers with carbon-carbon double bonds are added to each other to form a polymer without the generation of any by-product through the release of atoms. &#160;&#160;&#160;&#160;&#160;&#160;
Polymers that are made up of the same type of monomers are known as homopolymers, and those made up of different types of monomers are known as heteropolymers. Cellulose, the most abundant natural polymer, is a homopolymer of glucose, whereas agarose, a polymer of marine origin, is a heteropolymer of galactose and 3,6-anhydro-L-galactopyranose.
Polymers have various structures depending on their type of monomers. Linear polymers are long chains of monomers. For example, cellulose is a linear polymer held together by beta 1,4-glycosidic bonds.&#160;
Branched polymers have chains splitting off of the main chain, such as amylopectin, a component of starch that branches out after 24 to 30 monomers through alpha 1,6-glycosidic bonds.
Crosslinked polymers have two or more chains held together at several points like a ladder, such as a synthetically constructed silicon ladder polymer, or form a complex network of interlinked chains&#8212;like the gel formed by pectins in jellies and jams.

polymers

The word polymer is derived from the Greek words &#8220;poly&#8221; which means &#8220;many&#8221; and &#8220;mer&#8221; which means &#8220;parts&#8221;. Polymers are long chains of molecules composed of repeating units of smaller molecules, known as monomers. They either occur naturally, such as DNA and proteins, or can be constructed synthetically, like plastics. They have varied structural characteristics, such as linear chains, branched chains, or complex networks, that contribute to the properties that they exhibit. Additionally, functional groups that may be present on a polymer further define their properties. The individual units of a polymer are held together by stable covalent bonds that occur through either addition or condensation polymerization.
Addition Polymerization
Additional polymerization occurs when the monomers that participate in the reaction have double bonds. This reaction requires the presence of an external molecule that has an unpaired valence electron to initiate the reaction. This unpaired electron is highly reactive and forms a bond with one of the double bonds in a monomer, which leads to the monomer having an unpaired valence electron. This unpaired valence electron then associates with another monomer with double bonds leading to a chain reaction where the molecule keeps adding other monomers with double bonds to it. This results in the formation of a chain of monomers, with the one added most recently having an unpaired valence electron. This addition reaction continues until two chains with unpaired electrons react with each other to form a bond. This eliminates any unpaired valence electrons, resulting in the termination of the reaction.
Condensation Polymerization
Condensation polymerization, also known as step-growth polymerization, requires a catalyst, such as an acid or an enzyme, and the monomers must have at least two reactive functional groups, such as amines or carboxylic acids. Functional groups on monomers react with each other to form linkages such as ester or amide linkages and are accompanied by the loss of a small molecule, such as water. Condensation polymerization is a slower reaction compared to addition polymerization and, in many cases, requires the presence of heat.
This text is adapted from <a href="https://openstax.org/books/chemistry-2e/pages/Hydrocarbons">Openstax, Chemistry 2e, Chapter 20.1: Hydrocarbons</a>.

Polymers

The word polymer is derived from the Greek words &#8220;poly&#8221; which means &#8220;many&#8221; and &#8220;mer&#8221; which means &#8220;parts&#8221;. ...

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polymer chains and how they form

Polymers are long chains of molecules made from repeating units called monomers. The word polymer comes from the Greek words &quot;poly,&quot; meaning many, and &quot;mer,&quot; meaning parts. Polymers can be found in nature, such as DNA and proteins, or made synthetically, such as plastics.

A polymer’s shape helps define its properties. Some polymers form linear chains, while others are branched or arranged in complex networks. Functional groups on a polymer also affect how it behaves. The repeating units in a polymer are held together by stable covalent bonds.

Polymers can form through addition polymerization or condensation polymerization. Addition polymerization happens when monomers with double bonds react in the presence of an external molecule with an unpaired valence electron. That unpaired electron starts a chain reaction as monomers keep joining one after another. The reaction ends when two chains with unpaired electrons bond together and no unpaired electrons remain.

Condensation polymerization is also called step-growth polymerization. It needs a catalyst, such as an acid or an enzyme, and monomers must have at least two reactive functional groups, such as amines or carboxylic acids. These groups react to make linkages like esters or amides, and a small molecule such as water is lost. This process is slower than addition polymerization and often requires heat.

Polymer Chains and How They Form

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Polymers are long chains of molecules made from repeating units called monomers. The word polymer comes from the Greek words "poly," meaning many, and "mer," meaning parts. Polymers can be found in nature, such as DNA and proteins, or made synthetically, such as plastics. A polymer’s shape helps define its properties. Some polymers form linear chains, while others are branched or arranged in complex networks. Functional groups on a polymer also affect how it behaves. The repeating units in a...

key terms and concepts

Learn how polymers are built from monomers and how addition and condensation polymerization create natural and synthetic materials like DNA, proteins, and plastics.

Polymer Chains and How They Form | JoVE K12

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Polymer Chains and How They Form

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