Condensation polymerisation Flashcards
What is condensation polymerisation
The formation of two or more (usually different) monomers in a condensation reaction where a small molecule (usually water) is eliminated and a polymer is formed.
What are the key three condensation polymers we look at at a-level
Polyesters, polyamides and polypeptides
Describe how polyesters are formed
- Polyesters are formed from diols and docarboxylic acids
- The hydroxyl group and carboxyl group form an ester linkage and a molecule of water is eliminated per water bond formed.
- The -OH from the hydroxyl group and the hydrogen from the -OH of the carboxyl group form the molecule of water.
What is terylene
A polyester made from benzene-1,4- dicarboxylic acid and ethane-1,2-diol.
Describe how polyamides are formed
- Polyamides are formed from diaminoalkanes/diamines and dicarboxylic acids
- One of the hydrogens from the amine (-NH2) group reacts with the -OH from the carboxyl group to eliminate a molecule of water.
- The amide linkage is formed
What is Nylon-6,6
- A polyamide
- Industrially it is formed from 1,6-diaminohexane and hexane-1,6-dicarboxylic acid.
- In the lab it the reaction goes faster if a diacid chloride is used rather than the dicarboxylic acid: in this case, chlorine is eliminated.
What is Kevlar
- A polyamide
- Kevlar is made from benzene-1,4-diamine and benzene-1,4-dicarboxylic acid.
- Kevlar’s strength is due to the rigid chains and the ability of the flat aromatic rings to pack together held by strong intermolecular forces.
How are polypeptides formed
- Polypetides are a type of polyamide.
- In a polypeptide each amino acid has both an amine group and a carboxyl group.
- The amine group of one amino acid reacts with the carboxyl group of another.
- A molecule of water is formed per each bond formed.
Why are addition polymers not biodegradable
Addition polymers are basically long chain alkanes which are polar and unreactive.
How are addition polymers disposed of
- They are usually disposed of in landfill sites or by incineration.
- Some addition polymers can be melted and remoulded.
- Poly(alkenes) can be burnt to carbon dioxide and water to produce energy, although poisonous carbon monoxide may be produced as a result of incomplete combustion.
- Burning poly(alkenes) also adds to the problem of increasing the carbon dioxide level in the atmosphere.
- Other addition polymers can release toxic products upon burning such as toxic styrene gas.
Why are condensation polymers biodegradable
- Condensation polymers can be broken down by hydrolysis.
- This makes them biodegradable.
How are condensation polymers hydrolysed
In the presence of a strong acid or specific enzyme
Describe how to hydrolyse a polyester
Heat in 6-molar concentrated HCl. This process takes roughly 24 hours.
What are polyamides hydrolysed with
Hot, aqueous alkalis such as sodium hydroxide.