Polyesters and polyamides are example of condensation polymers. They are strong due to their polar bonds. The polymers are represented using repeat units and can be determined by the monomers. Condensation polymers contain ester and/or amide links.

Condensation polymerisation

Condensation polymerisation occurs when monomers with two different functional groups are joined together by the elimination of a small molecule such as water or hydrogen chloride.

Example

Examples of condensation polymers are polyesters, polyamides, polypeptides and proteins.

Polyesters

Polyesters are formed by reacting together a hydroxyl and a carboxyl, giving rise to an ester link. Polyesters are essentially a long chain of ester molecules.

Chemistry; Organic chemistry III; KS5 Year 12; Condensation polymers

Example

Polyamides

Polyamides are formed by reacting together an amine and a carboxyl group together, giving rise to an amide link. Polyamides are essentially a long chain of amide molecules.

Example

Polypeptides and proteins

Amino acids contain both an amine and a carboxyl group. Polypeptides and proteins are formed by reacting amino acids together, giving rise to an amide link. The amide links in polypeptides and proteins are called peptide links. Proteins are the assembly of two or more polypeptides.

Repeat unit

Since polymers are (very) large molecules they are represented using repeat units in the displayed formula.

To draw a repeat unit:

PROCEDURE

1.	Draw the monomers near each other.
2.	Draw brackets around the two monomers.
3.	Remove the $OH$ of the carboxyl group(s).
4.	Remove one $H$ atom from the amine group(s) or the alcohol group(s).
5.	If it's a polyester, join the carbon (of the carbonyl group) and the oxygen (initially part of a hydroxyl group) next each other. If it's a polyamide or polypeptide, join the carbon (of the carbonyl group) and the nitrogen (of the amine) near each other.
6.	Extend the bonds at the ends of the repeat unit. Ensure they extend outside the brackets as it indicates that the chain is longer.
7.	Add a subscript 'n' on the bottom right hand corner. This indicates a large number of repeat units.

Example

Identifying the monomer

The monomers can be identified from the repeat unit.

PROCEDURE

1.	Find the ester/amide link in the repeat unit.
2.	Break the bond of the ester/amide link.
3.	Add $OH$ to any carbon atoms at the end of the molecule. This will reform your carboxyl group.
4.	Add a $H$ to any nitrogen or oxygen atoms at the end of the molecule. This will give you your amine or alcohol group.

Example

The monomers for the polyamide shown to the left are $1,3$ -diamonopropane and heptane- $1,7$ -dicarboxylic acid.

Condensation polymers are strong

Condensation polymers tend to be strong. This is due to the polar bonds in these polymers which give rise to hydrogen bonding and permanent dipole-dipole interactions, on top of the van der Waals forces.

Complex condensation polymers

Molecules with both an amine and an alcohol group can react with dicarboxylic acids. The polymers formed will contain amide and ester links.

Example

Molecules containing both a carboxyl group and an amine/alcohol group can undergo polymerisation with itself i.e. only one type of monomer is required for polymerisation, as the monomer contains the desired reactive functional groups.

Example

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Unit 1

Ceramics, polymers and composites

Unit 2

Polymers

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Unit 3

Condensation polymers

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FAQs - Frequently Asked Questions

What are peptide links?

The amide links in polypeptides and proteins are called peptide links.

How are polyamides formed?

Polyamides are formed by reacting together an amine and a carboxyl group together.

What are examples of condensation polymers?

Examples of condensation polymers are polyesters, polyamides, polypeptides and proteins.

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Summary

Condensation polymers

In a nutshell

Condensation polymerisation

Condensation polymerisation occurs when monomers with two different functional groups are joined together by the elimination of a small molecule such as water or hydrogen chloride.

Example

Examples of condensation polymers are polyesters, polyamides, polypeptides and proteins.

Polyesters

Polyesters are formed by reacting together a hydroxyl and a carboxyl, giving rise to an ester link. Polyesters are essentially a long chain of ester molecules.

Example

Polyamides

Polyamides are formed by reacting together an amine and a carboxyl group together, giving rise to an amide link. Polyamides are essentially a long chain of amide molecules.

Example

Polypeptides and proteins

Repeat unit

Since polymers are (very) large molecules they are represented using repeat units in the displayed formula.

To draw a repeat unit:

PROCEDURE

1.	Draw the monomers near each other.
2.	Draw brackets around the two monomers.
3.	Remove the $OH$ of the carboxyl group(s).
4.	Remove one $H$ atom from the amine group(s) or the alcohol group(s).
5.	If it's a polyester, join the carbon (of the carbonyl group) and the oxygen (initially part of a hydroxyl group) next each other. If it's a polyamide or polypeptide, join the carbon (of the carbonyl group) and the nitrogen (of the amine) near each other.
6.	Extend the bonds at the ends of the repeat unit. Ensure they extend outside the brackets as it indicates that the chain is longer.
7.	Add a subscript 'n' on the bottom right hand corner. This indicates a large number of repeat units.

Example

Identifying the monomer

The monomers can be identified from the repeat unit.

PROCEDURE

1.	Find the ester/amide link in the repeat unit.
2.	Break the bond of the ester/amide link.
3.	Add $OH$ to any carbon atoms at the end of the molecule. This will reform your carboxyl group.
4.	Add a $H$ to any nitrogen or oxygen atoms at the end of the molecule. This will give you your amine or alcohol group.

Example

The monomers for the polyamide shown to the left are $1,3$ -diamonopropane and heptane- $1,7$ -dicarboxylic acid.

Condensation polymers are strong

Complex condensation polymers

Molecules with both an amine and an alcohol group can react with dicarboxylic acids. The polymers formed will contain amide and ester links.

Example

Learn with Basics

Length:

Unit 1

Ceramics, polymers and composites

Unit 2

Polymers

Jump Ahead

Optional

Unit 3

Condensation polymers

Final Test

Create an account to complete the exercises

FAQs - Frequently Asked Questions

What are peptide links?

The amide links in polypeptides and proteins are called peptide links.

How are polyamides formed?

Polyamides are formed by reacting together an amine and a carboxyl group together.

What are examples of condensation polymers?

Examples of condensation polymers are polyesters, polyamides, polypeptides and proteins.