Condensation polymers are everywhere around us! They're used in clothes, sports equipment, and even in our own cells. But what exactly are they? Well, they're a type of polymer that's made through a reaction called condensation.

Basically, condensation polymers are made by linking two smaller molecules (called monomers) together and releasing a small molecule in the process. This reaction is what gives condensation polymers their unique properties. In this article, we'll explore the world of condensation polymers in organic chemistry. We'll start by taking a general look at how they're made, and then dive into some specific examples. Plus, you'll have the chance to practice drawing condensation polymers and their monomers! We'll also talk about the intermolecular forces found between condensation polymer chains, and compare them to another type of polymer called addition polymers. So if you're interested in learning more about the science behind the things we use every day, keep reading! And remember, condensation polymers are key players in the world of materials science.

Condensation reactions of polymers

Polymer compounds are made up of repeating units called monomers. When a polymer is formed using a condensation reaction, it's called a condensation polymer. During this reaction, two molecules are joined together by removing a smaller molecule, usually water, which is known as a condensate. Condensation polymers are made from smaller monomers, which can be identical or different molecules. Each monomer needs to have two functional groups, one at each end. If a monomer has two different functional groups, such as a hydroxyl group and a carboxyl group, it can form a condensation polymer by linking up with other molecules of the same type. However, if it contains two of the same functional group, it requires a different type of monomer to form a condensation polymer.

Types of condensation polymers

There are three main types of condensation polymers: polyamides, polyesters, and polypeptides. Each of these polymers is created using different monomers, and they get their names from the type of link that's formed during polymerization.

Polyamides are polymers that have amide links, while polyesters have ester links. Polypeptides, on the other hand, have peptide links. All three of these polymers have unique properties and are used in various applications. It's also worth noting that starches and other polysaccharides are also condensation polymers. They're formed through a condensation reaction between monosaccharides and are joined together by a glycosidic bond. If you're interested in learning more about carbohydrates and the different types of polysaccharides, be sure to check out our article on the topic!

Polyamides

Polyamides are condensation polymers that contain the amide linkage group, -NHCO-. Here's a molecule. It has the amide functional group, -NHCO-. This consists of an amine group bonded to a carbonyl group - or in other words, a nitrogen atom bonded to a C=O.

‍

Polyamides are long polymers made from lots of smaller monomers joined together by amide groups. We call these amide linkages. Like all condensation polymers, they're made in a condensation reaction; in this case, the condensate released is water.

Polyamides can be made from a variety of different reactants. Here's an example of making a polyamide from a diamine and a dicarboxylic acid. A hydroxyl (-OH) group from the dicarboxylic acid reacts with a hydrogen atom from one of the diamine's amine groups, forming water. This results in an amide linkage between the diamine and the dicarboxylic acid. Because both molecules have two functional groups, one at each end, the process happens again. This creates a long polyamide polymer chain.

‍

You should note that in this diagram, and in all of the condensation polymer diagrams in this article, we've shown what happens when you react just two monomers together. But remember that polymers are extremely large molecules. In fact, they consist of many hundreds of monomers joined together in a long chain - not just two monomers. If we were to show the whole polymer, it wouldn't fit on the page!

Polyesters

Polyesters are condensation polymers that contain the ester linkage group, -COO-.

Let's look at another type of molecule. This one has an ester functional group, -COO-.

‍

Polyesters are long polymers created through a condensation reaction between many smaller monomers, which releases water. Unlike polyamides, polyesters contain the ester linkage.

Polyesters can be made from a variety of reactants, including a diol and a dicarboxylic acid, a diol and a dioyl chloride, and a hydroxycarboxylic acid. For example, a polyester can be made from a diol and a dicarboxylic acid by having the hydroxyl group (-OH) from the dicarboxylic acid react with a hydrogen atom from one of the diol's hydroxyl groups, resulting in the formation of water. This reaction creates an ester linkage group between the dicarboxylic acid and the diol. Since both molecules have two functional groups, the process repeats itself, resulting in the formation of a long polyester polymer.

‍

‍

Polypeptides

Polypeptides are a type of polyamide. They are condensation polymers that are made from amino acids and contain the amide linkage group, -NHCO-.

Polypeptides are also a type of polyamide, containing the amide functional group. However, instead of needing two different monomers, they are made from just one type of monomer: an amino acid. Amino acids are organic molecules that contain both the amine (-NH2) and carboxyl (-COOH) functional groups. They're the building blocks of proteins.

‍

That's correct! Amino acids contain both the amine and carboxyl functional groups, which allows them to react with each other without the need for a different type of monomer. The amine group from one amino acid reacts with the carboxyl group of another, forming an amide linkage group and releasing water as a condensate. When two amino acids join together, they form a dipeptide, but the process repeats itself, resulting in the formation of a long polymer chain known as a polypeptide. Polypeptides are also known as proteins and have various functions in biological systems.

‍

‍

To learn more about amino acids, head over to Amino Acids. If polypeptides caught your attention, we have a couple of resources you'll want to read. Check out Proteins Biochemistry for a chemistry-focused view on these polymers, or visit Proteins for a look through a biologist's eyes.

Condensation polymer examples

Let's move on to having a look at examples of condensation polymers. In particular, we'll focus on examples of polyamides and polyesters. These include: Nylon-6,6KevlarTerylene

Nylon-6,6

Nylon-6,6 is an example of a polyamide. It is made in a condensation reaction between 1,6-diaminohexane and hexane-1,6-dicarboxylic acid. This releases water.

‍

Reacting different diamines and dicarboxylic acids produces different types of nylon. For example, reacting 1,6-diaminohexane and decane-1,10-dicarboxylic acid produces nylon-6,10. You can also produce nylon by reacting a diamine with a dioyl chloride, such as hexanedioyl. This releases hydrochloric acid instead of water. Nylon is used not only in various clothing and textiles, from carpets and jumpers to horse turnout rugs, but also in zip ties and hoses.

Kevlar

Kevlar is another example of a polyamide. It's made by reacting benzene-1,4-diamine with benzene-1,4-dicarboxylic acid in a condensation reaction, releasing water.

‍

Kevlar has an extremely high tensile strength to weight ratio, making it perfect for bulletproof vests and racing sails. It is also used in the science industry to separate vacuum-sealed containers from areas under normal atmospheric pressure.

Terylene

The final example of a polymer we'll look at today is Terylene. Terylene is a polyester, made from ethane-1,2,diol and benzene-1,4-dicarboxylic acid in a condensation reaction. Once again, this releases water as the condensate.

‍

Terylene is commonly known as PET and is used for clothing, wet weather gear, food packaging, and microfibre towels.

Condensation polymers structure

In your exam, you need to know how to identify not only the condensation polymer made from two monomers, but also the monomers used to make a condensation polymer. Let's give this a go.

‍

To identify the condensation polymer from the monomer, we first need to identify the small molecule that is lost during the condensation reaction. In the case of a diol and a dicarboxylic acid, the molecule released is water. We then remove the atoms that make up this small molecule from the monomers and join the remaining atoms together, forming a polymer. This process results in the formation of a polyester. Alternatively, we can identify the parts of the monomers that form the ester linkage and join them together to create the polymer. Either approach can be used to create the same polymer in the end.

‍

‍

For your exam, you don't need to be able to name condensation polymers; simply draw their structures from the monomers given. Let's now try the reverse: identifying the monomers that make up a condensation polymer.

‍

That's correct! The polymer described contains the amide functional group and is therefore a polyamide. Polyamides can be made in different ways, but in this case, the monomers are a diamine and a dicarboxylic acid.

During the condensation reaction that forms the polyamide, the diamine loses a hydrogen atom, and the dicarboxylic acid loses a hydroxyl group (-OH), which react together to form a water molecule. The diamine and dicarboxylic acid then join together using an amide linkage group. To break down the polyamide, we add water, which splits the polymer down the middle of the amide group, adding a hydrogen atom to the amine and a hydroxyl group to the carboxylic acid. This process returns us to the original monomers, in this case, 1,2-diaminoethane and benzene-1,4-dicarboxylic acid.

‍

‍

Breaking a condensation polymer using water involves a hydrolysis reaction. This is how condensation polymers are broken down after we are finished with them. You'll learn all about this in Polymer Disposal.

Condensation polymers and intermolecular forces

Both polyamides and polyesters experience permanent dipole-dipole forces between polymer chains due to the polar nature of their amide and ester functional groups. However, polyamides can also form hydrogen bonds due to the presence of a nitrogen atom bonded to a hydrogen atom in their amide functional group. These intermolecular forces increase the strength of polyamides and polyesters.

Depending on the structure of the monomers used to make polyesters, hydrogen bonding between polyester polymer chains may also be possible. For example, if one of the monomers contains a hydroxyl group (-OH), it can form hydrogen bonds with neighboring chains. However, the strongest intermolecular forces present between all polyester chains are permanent dipole-dipole forces.

Addition and Condensation Polymers

That's a great summary! Just to add on, addition polymers are formed through the addition of monomers with unsaturated double bonds. The double bond breaks, and the monomers add together to form a long chain polymer. Addition polymers do not involve any elimination of small molecules, unlike condensation polymers. Examples of addition polymers include polyethylene, polypropylene, and polystyrene.

In terms of properties, condensation polymers tend to have higher melting and boiling points, as well as greater strength and stiffness compared to addition polymers. This is due to the presence of intermolecular forces between polymer chains in condensation polymers. Addition polymers, on the other hand, tend to have lower melting and boiling points, and are more flexible and less brittle.

Overall, both condensation and addition polymers have their own unique properties and applications in various industries. Understanding the differences between the two can help in selecting the appropriate polymer for a particular use.

Addition Polymers - Key takeaways

Addition polymers are polymers formed through the addition of monomers with unsaturated double bonds.

Examples of addition polymers include polyethylene, polypropylene, and polystyrene.

Addition polymers do not involve elimination of small molecules, unlike condensation polymers.

Addition polymers tend to have lower melting and boiling points, and are more flexible and less brittle compared to condensation polymers.

Overall, understanding the differences between addition and condensation polymers can help in selecting the appropriate polymer for a particular use.

Condensation Polymers

What is the difference between addition and condensation polymers?

The main difference between addition and condensation polymers is the reaction used to form them. Condensation polymers are formed in condensation reactions between molecules with different functional groups. Addition polymers are formed in addition reactions between molecules with a double bond.

What is a condensation polymer?        

Condensation polymers are polymers made in a condensation reaction between two monomers, releasing a small molecule in the process.

What happens in a condensation reaction?

In a condensation reaction, a molecule of water is formed by removing a hydrogen atom from one monomer and a hydroxyl group from another monomer. This results in a covalent bond between the two monomers.

Is polypropylene a condensation polymer?

Polypropylene is not a condensation polymer, as the reaction which forms chains of polypropylene from propylene monomers is an addition reaction, not a condensation reaction.

What are examples of condensation polymers?

Examples of condensation polymers include polyamides, polyesters, and polypeptides.

‍