Polyesters and polyamides
All You Need in One PlaceEverything you need for better marks in primary, GCSE, and A-level classes. | Learn with ConfidenceWe’ve mastered the UK’s national curriculum so you can study with confidence. | Instant and Unlimited Help24/7 access to the best tips, walkthroughs, and practice questions. |
Make math click 🤔 and get better grades! 💯Join for Free
0/3
Intros
0/2
Examples
Lessons
- Show the repeating units of the condensation polymer formed by the following compounds.
- Show the repeating units of the condensation polymer that can be formed by these pairs of compounds:
- 3,3-dimethylhexane-1,6-diol and benzene-1,4-dioic acid.
- Ethane-1,2-diamine and butanedioic acid.
- Show the expected monomer units of the following condensation polymers.
Below are the repeat units of two condensation polymers.- Draw the monomer units of both polymers showing the functional groups that take part in the condensation polymerisation.
Free to Join!
StudyPug is a learning help platform covering maths and science from primary all the way to second year university. Our video tutorials, unlimited practice problems, and step-by-step explanations provide you or your child with all the help you need to master concepts. On top of that, it's fun — with achievements, customizable avatars, and awards to keep you motivated.
Easily See Your Progress
We track the progress you've made on a topic so you know what you've done. From the course view you can easily see what topics have what and the progress you've made on them. Fill the rings to completely master that section or mouse over the icon to see more details.Make Use of Our Learning Aids
Earn Achievements as You Learn
Make the most of your time as you use StudyPug to help you achieve your goals. Earn fun little badges the more you watch, practice, and use our service.Create and Customize Your Avatar
Play with our fun little avatar builder to create and customize your own avatar on StudyPug. Choose your face, eye colour, hair colour and style, and background. Unlock more options the more you use StudyPug.
Topic Notes
In this lesson, we will learn:
- How condensation polymers (polyesters and polyamides) are made.
- To identify the repeating units of condensation polymers.
- Some important commercial examples of condensation polymers.
- How condensation polymers occur naturally with amino acids.
Notes:
- Polyesters and polyamides are both examples of condensation polymers. As a type of polymer, these can have very desirable properties, and some important industrially-made materials are polyamides or polyesters.
- We saw polyesters in Carboxylic acids, acyl chlorides and esters when diols and dioic acids (AKA dicarboxylic acids) react. This is a simple esterification but instead of just a carboxylic acid and alcohol, the diol and dioic acid make it happen at both ends of each molecule, and so a large polymer chain emerges.
The repeating unit of a polyester will contain one complete ester linkage and the next ester linkages cut in half. This should contain one of the diols and one of the dioic acids. For an example see below: - Polyamides are made the same way as polyesters, but they have a -CONH- amide linkage instead of a -COOR- ester linkage.
As we saw last time in Carboxylic acids, acyl chlorides and esters, the reaction of a carboxylic acid and an amine (or ammonia) produces an amide. In exactly the same way as diols and dioic acids make polyesters, diamines and dioic acids produce polyamides.
This is a condensation polymer product.
One important example is nylon-6,6. See the image below: - The amide linkage in polyamides is also present when amino acids combine to form ‘polymer’ chains. Amino acids are molecules containing both an amine and a carboxylic acid group, usually at opposite ends of the molecule. The naturally-occurring amino acids have four key components:
- An amino group (-NH2).
- A carboxylic acid group (-COOH).
- An R group attached to the carbon bonded to the amino group. This R group is what identifies an amino acid. It can be as simple as hydrogen (in glycine) or much larger, involving rings, heteroatoms or hydrocarbon chains.
- An H atom bonded to the carbon which is bonded to the R group. This is important because this carbon atom, except in glycine, is now a chiral centre.
This is a condensation polymerisation to make polyethylene terephthalate (PET). It is a common polyester used in making plastic bottles and some clothing.
Look at how the repeating unit is drawn: one complete ester linkage (which joins the diol and the dioic acid).
Ester linkages in small molecules are relatively strong chemical bonds, but dilute acid and alkali can hydrolyse them. In polyesters, acid hydrolysis is extremely slow and only alkali/basic solution can reasonably break it down .
This condensation polymerisation has two units joining together: hexanedioic acid and hexane-1,6-diamine. These form the polyamide nylon-6,6.
The 6,6 is named because both monomers that form the repeating unit are 6 carbons in length (the hexanedioic acid and hexane-1,6-diamine).
Another example is Kevlar which is uses in bulletproof vests. The monomers for this polyamide are benzene-1,4-dioic acid and benzene-1,4-diamine. See the image below:
Amide linkages are more resistant to hydrolysis in general than ester linkages. This helps make the polymer relatively strong, but its intermolecular hydrogen bonding gives Kevlar its strength.
The many benzene rings in each long polymer chain keep them relatively flat and straight. This enables separate polyamide chains to align, both aside and on top of one another. This close alignment with other chains allows hydrogen bonding to occur between intermolecular amide groups. These attractive forces accumulate throughout the very long polyamide chains making the combined mass extremely strong and hard to tear or pull apart.
This is like creating a strong rope out of many individual fibres, which are weak on their own. The whole is greater than the sum of its parts!
Just like polyamides made from an amine and acid group, amino acids can polymerise using both of these groups. Polymers made of amino acid monomers are called proteins, and they are formed by condensation reactions just like how polyamides are formed. When we study it in proteins, the amide link is called a peptide bond. See the image below, where glycine (gly) and alanine (ala) form a peptide bond:
In this example, it is just a combination of two molecule. The product can be called “gly-ala” as it is a unit comprised of both amino acids with a peptide bond.
As said above, it is the same bond making as in polyamides, but there are many different amino acids and they form very complex sequences – they’re the building blocks of life.
We will learn more about amino acids in a later lesson!
2
videos
remaining today
remaining today
5
practice questions
remaining today
remaining today