Condensation polymerisation

Question 1

What is condensation polymerisation

Answer 1

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.

Question 2

What are the key three condensation polymers we look at at a-level

Answer 2

Polyesters, polyamides and polypeptides

Question 3

Describe how polyesters are formed

Answer 3

• 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.

Question 4

What is terylene

Answer 4

A polyester made from benzene-1,4- dicarboxylic acid and ethane-1,2-diol.

Question 5

Describe how polyamides are formed

Answer 5

• 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

Question 6

What is Nylon-6,6

Answer 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.

Question 7

What is Kevlar

Answer 7

• 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.

Question 8

How are polypeptides formed

Answer 8

• 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.

Question 9

Why are addition polymers not biodegradable

Answer 9

Addition polymers are basically long chain alkanes which are polar and unreactive.

Question 10

How are addition polymers disposed of

Answer 10

• 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.

Question 11

Why are condensation polymers biodegradable

Answer 11

• Condensation polymers can be broken down by hydrolysis.
• This makes them biodegradable.

Question 12

How are condensation polymers hydrolysed

Answer 12

In the presence of a strong acid or specific enzyme

Question 13

Describe how to hydrolyse a polyester

Answer 13

Heat in 6-molar concentrated HCl. This process takes roughly 24 hours.

Question 14

What are polyamides hydrolysed with

Answer 14

Hot, aqueous alkalis such as sodium hydroxide.