Condensation Polymers
Quick Notes
- Condensation polymers form when monomers with two reactive functional groups join together, releasing a small molecule such as H2O or HCl.
- Common condensation polymer formation:
- Dicarboxylic acids + Diols → Polyesters
- Dicarboxylic acids + Diamines → Polyamides
- Amino acids → Polypeptides (Proteins)
- Examples:
- Polyesters → Terylene (PET) (often used as a material fabric or for making plastic bottles and ropes)
- Polyamides → Nylon 6,6 (often used for synthetic clothing) and Kevlar (often used as a non-slip coating).
- Polymer properties depend on intermolecular forces (hydrogen bonding, dipole–dipole, van der Waals).
Full Notes
Polymers are formed when monomers react together to create a (very) large molecule made up of repeating units.
Condensation polymers are formed when monomers react together and a small molecule is released (commonly water or HCl) as the monomers form repeating units. The formation of condensation polymers is called condensation polymerisation.
Condensation polymers are broken apart in hydrolysis reactions - the opposite of condensation, where a small molecule (usually water) is added back into the polymer to break up the repeating units.
There are lots of different types of condensation polymer (many human made and naturally occurring). Common examples include polyesters and polyamides.
Formation of Polyesters
Polyesters can be formed by the reaction of a dicarboxylic acid with a diol.
Ester link (-COO-) is formed with the loss of water and further ester links can be made to each end of the ester formed between other dicarboxylic acids and diols.
Example: Terylene (PET) Formation
Monomers: Benzene-1,4-dicarboxylic acid + Ethane-1,2-diol
Uses: Clothing fabrics, plastic bottles, food packaging.
Formation of Polyamides
Polyamides are formed by the reaction of a dicarboxylic acid with a diamine.
Amide link (-CONH-) is formed with the loss of water and further amide links can be made to each end of the amide formed between other dicarboxylic acids and diamines.
Example:Nylon 6,6 Formation
Monomers: Hexanedioic acid + 1,6-diaminohexane
Uses: Fibres for clothing, ropes, parachutes.
Example:Kevlar Formation
Monomers: Benzene-1,4-dicarboxylic acid + Benzene-1,4-diamine
Uses: Bulletproof vests, helmets, reinforced tyres.
Formation of Polypeptides (Proteins)
Amino acids polymerise to form polypeptides via peptide bonds (-CONH-).
This polymerisation is essential for the forming of proteins in biological systems (see Proteins and Amino Acids for more).
Intermolecular Forces in Condensation Polymers
The type of intermolecular force(s) between polymer molecules is based on the monomers that react to form the polymer and influence the physical properties of the polymer.
| Polymer Type | Intermolecular Forces | Strength |
|---|---|---|
| Polyesters | Dipole-dipole & van der Waals | Moderate |
| Polyamides (Nylon/ Kevlar) | Hydrogen bonding | Stronger |
| Polypeptides (Proteins) | Hydrogen bonding | Very strong |
Polyamides (e.g., Kevlar) are very strong due to extensive hydrogen bonding.
Polyesters rely on dipole–dipole and van der Waals forces, making them weaker.
Summary
- Condensation polymers form when monomers join with the loss of a small molecule (often H2O or HCl).
- Polyesters form from dicarboxylic acids + diols; polyamides form from dicarboxylic acids + diamines; amino acids form polypeptides.
- Key examples: Terylene (PET), Nylon 6,6 and Kevlar.
- Hydrolysis breaks condensation polymers back to monomers by addition of water.
- Properties depend on intermolecular forces: strong hydrogen bonding in polyamides versus weaker dipole/van der Waals in many polyesters.