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Condensation Polymers

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Condensation Polymers

Condensation polymers are an extremely common type of polymer. They are used in clothes, sports equipment, and within our own cells. There are lots of types of condensation polymers, but the theme that links them all together is the reaction by which they're made - a condensation reaction.

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

  • This article is about condensation polymers in organic chemistry.
  • We'll take a general look at how condensation polymers are made, before exploring some specific examples of condensation polymers.
  • You'll be able to practice drawing condensation polymers and the monomers that make them up.
  • After that, we'll look at the intermolecular forces found between condensation polymer chains.
  • We'll finish by comparing condensation and addition polymers.

Condensation reactions of polymers

If a polymer is a compound made from several repeating units called monomers, then a condensation polymer is just a polymer that is formed using a condensation reaction. A condensation reaction is a chemical reaction that joins two molecules by removing a smaller molecule, commonly water. This small molecule is known as a condensate.

Condensation polymers are made from smaller monomers. These monomers can be exactly the same molecule or totally different. However, each monomer needs two functional groups, one at each end. If the monomer has two different functional groups, say both a hydroxyl group and a carboxyl group, then great - it can form a condensation polymer by joining up with other molecules of itself. But if it contains two of the same functional group, you'll need another type of monomer as well.

Types of condensation polymers

There are a few important types of condensation polymers.

  • Polyamides
  • Polyesters
  • Polypeptides

These condensation polymers are created using different monomers, getting their names from the type of link formed during polymerisation. For example, polyamides have amide links, polyesters have ester links, and polypeptides have peptide links.

We'll focus on all three of these polymers here.

Did you know that starches and other polysaccharides are also condensation polymers? They're made in a condensation reaction between monosaccharides and are joined by a glycosidic bond. Check out Carbohydrates and Types of Polysaccharides for more.

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.

Condensation Polymers, Amide functional group, StudySmarterAmide functional group. Anna Brewer, StudySmarter Original

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.

  • A diamine and a dicarboxylic acid.
  • A diamine and a dioyl chloride.
  • Two aminocarboxylic acids.
  • Two amino acids.

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.

Condensation Polymers, polymerisation reaction between a diamine and a dicarboxylic acid, StudySmarterThe polymerisation reaction between a diamine and a dicarboxylic acid creates a polyamide and water. Anna Brewer, StudySmarter Original

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-.

Condensation Polymers, Ester functional group, StudySmarterThe ester functional group. Anna Brewer, StudySmarter Original

Polyesters are long polymers made from many smaller monomers in a condensation reaction, releasing water. This is very much like polyamides. But unlike polyamides, polyesters contain the ester linkage.

Polyesters can be made from a variety of different reactants:

  • A diol and a dicarboxylic acid.
  • A diol and a dioyl chloride.
  • A hydroxycarboxylic acid.

Here's an example of making a polyester from a diol and a dicarboxylic acid. Similar to the reaction that makes a polyamide, a hydroxyl (-OH) group from the dicarboxylic acid reacts with a hydrogen atom from one of the diol's hydroxyl groups, forming water. This results in an ester linkage group between the dicarboxylic acid and the diol. Because both molecules have two functional groups, one at each end, the process happens again. This creates a long polyester polymer.

Condensation Polymers, polymerisation reaction between a diol and a dicarboxylic acid, StudySmarter

The polymerisation reaction between a diol and a dicarboxylic acid creates a polyester and water. Anna Brewer, StudySmarter Original

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.

Condensation Polymers, amino acid, StudySmarterAn amino acid. Anna Brewer, StudySmarter Original

Because amino acids contain both the amine functional group and the carboxyl functional group, they don't need a different type of monomer with which to react - they can react with each other. The amine group from one amino acid reacts with the carboxyl group of another, joining the two together using an amide linkage group. This is another example of a condensation reaction that releases water as a condensate. When just two amino acids join together, it forms a dipeptide, but the process repeats, forming a long polymer chain known as a polypeptide. Polypeptides are also called proteins.

Condensation Polymers, polymerisation reaction between two amino acids, StudySmarterThe polymerisation reaction between two amino acids creates a polypeptide and water. Anna Brewer, StudySmarter Original

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-6,6
  • Kevlar
  • Terylene

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.

Condensation Polymers, nylon-6,6, StudySmarterProducing nylon-6,6. Anna Brewer, StudySmarter Original

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.

Condensation Polymers, Kevlar, StudySmarterMaking Kevlar. Anna Brewer, StudySmarter Original

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.

Condensation Polymers, Terylene, StudySmarterMaking Terylene. Anna Brewer, StudySmarter Original

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.

Draw the condensation polymer formed from the following two monomers:

Condensation Polymers, monomer polymer structure prediction, StudySmarterPredicting the polymer from the monomers. Anna Brewer, StudySmarter Original

To find the condensation polymer from the monomer, we first need to identify the small molecule that is lost in the condensation reaction. Here, we are reacting a diol with a dicarboxylic acid, so the molecule released will be water. We then identify exactly which atoms are lost to make this small molecule. Here, we lose two hydrogen atoms and an oxygen atom. We then take these atoms away from monomers and join the monomers together, forming a polymer. Here, we make a polyester.

Alternatively, you could identify the parts of the monomers that form the ester linkage. When you join these together, you create the polymer.

Condensation Polymers, monomer polymer structure prediction, StudySmarterPredicting the polymer from the monomers. Anna Brewer, StudySmarter Original

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.

Draw and name the diamine and dicarboxylic acid that make up this condensation polymer.

Condensation Polymers, monomer polymer structure prediction, StudySmarterPredicting the monomers from the polymer. Anna Brewer, StudySmarter Original

Firstly, we can see that this polymer contains the amide functional group. It is therefore a polyamide. We know that polyamides can be made in different ways, but the question tells us that in this case, the monomers are a diamine and a dicarboxylic acid.

Remember how polyamides are formed when diamines and dicarboxylic acids react in a condensation reaction? 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 the dicarboxylic acid then join using an amide linkage group.

To break a polyamide, we do the reverse - we add water. Adding water 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 leaves us with our monomers. In this case, we are left with 1,2-diaminoethane and benzene-1,4-dicarboxylic acid.

Condensation Polymers, monomer polymer structure prediction, StudySmarterPredicting the monomers from the polymer. Anna Brewer, StudySmarter Original

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

We've learned about the bonding within long condensation polymer chains. For example, polyamides are joined using the amide linkage group, and polyesters are joined using the ester linkage group. But what about the bonding between condensation polymer chains?

Well, both the amide functional group and the ester functional group are polar. This means that both polyamides and polyesters experience permanent dipole-dipole forces between polymer chains. However, the amide functional group contains a nitrogen atom bonded to a hydrogen atom. This means that polyamides can also form hydrogen bonds. These intermolecular forces increase the strength of polyamides and polyesters.

Depending on the structure of the rest of the monomers used to make polyesters, you could also find hydrogen bonding between polyester polymer chains. For example, one of the monomers might contain a hydroxyl group, -OH. These are able to form hydrogen bonds. However, the strongest intermolecular forces that you are guaranteed to find between all polyester chains are permanent dipole-dipole forces.

Addition and Condensation Polymers

To finish, let's compare condensation polymers with addition polymers.

Not too sure about addition polymers? Check out Polymerisation Reactions for more.

Condensation polymersAddition polymers
Name of polymerPolyamide, polyester, polypeptidePoly(alkene)
Number of different types of functional groups required21
Functional groups involved-COOH, -NH2, -OHC=C
Polymerisation reaction usedCondensationAddition
Additional product formedCondensate, often waterNone
DisposalHydrolysisCan't be broken down easily

That's it!

By now, you should know what condensation polymers are, and how various examples are made. You should also be able to draw the condensation polymer formed from two given monomers, and deconstruct a polymer down into its monomers. Finally, you should have an understanding of the intermolecular forces between condensation polymer chains, and the differences between addition and condensation polymers.

Condensation Polymers - Key takeaways

  • Condensation polymers are polymers made in a condensation reaction between two smaller monomers, releasing a small molecule called a condensate in the process.
  • Polyamides, polyesters, and polypeptides are all examples of condensation polymers.
    • Polyamides contain the amide linkage group, and are typically made from a diamine and a dicarboxylic acid.
    • Polyesters contain the ester linkage group, and are typically made from a diol and a dicarboxylic acid.
    • Polypeptides are a type of polyamide, and are made from amino acids.
  • Condensation polymers can be broken down in a hydrolysis reaction.
  • Condensation polymers are polar, meaning that they experience permanent dipole-dipole forces between chains. Polyamides also experience hydrogen bonds.

Frequently Asked Questions about 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.

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

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.

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.

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

Final Condensation Polymers Quiz

Question

What are condensation polymers?

Show answer

Answer

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

Show question

Question

True or false? Condensation reactions produce just one product.

Show answer

Answer

False

Show question

Question

Which monomer(s) can be used to make a polyamide?

Show answer

Answer

A diamine and a dicarboxylic acid

Show question

Question

Which of the following are condensation polymers?

Show answer

Answer

Polyamides

Show question

Question

What is the amide linkage group?

Show answer

Answer

-NHCO-

Show question

Question

Which monomer(s) can be used to make a polyester?

Show answer

Answer

A diol and a dicarboxylic acid

Show question

Question

What is the ester linkage group?

Show answer

Answer

-COO-

Show question

Question

Describe the basic structure of a polypeptide.

Show answer

Answer

Polypeptides are made from multiple amino acids joined together by amide linkage groups.

Show question

Question

What monomer(s) are used to make polypeptides?

Show answer

Answer

Proteins

Show question

Question

What is the strongest type of intermolecular force that you find between all polyester chains?

Show answer

Answer

Permanent dipole-dipole forces

Show question

Question

What is the strongest type of intermolecular force that you find between all polyamide chains?

Show answer

Answer

Hydrogen bonding

Show question

Question

How do you break down condensation polymers?

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Answer

In a hydrolysis reaction, which requires water

Show question

Question

Give two uses of nylon.

Show answer

Answer

  • Clothing
  • Textiles
  • Zip ties
  • Hoses

Show question

Question

Give two uses of Kevlar.

Show answer

Answer

  • Bulletproof vests
  • Racing sails
  • Vacuum seals

Show question

Question

Give two uses of Terylene.

Show answer

Answer

  • Clothing
  • Wet weather gear
  • Food packaging
  • Microfibre towels

Show question

Question

What type of polymer is nylon?

Show answer

Answer

A polyamide

Show question

Question

What type of polymer is Kevlar?

Show answer

Answer

A polyamide

Show question

Question

What type of polymer is Terylene?

Show answer

Answer

A polyester

Show question

Question

Which two functional groups do amino acids contain?

Show answer

Answer

Carboxyl  group

Show question

Question

True or false? Forming a polypeptide requires two different types of monomer.

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Answer

False

Show question

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