6.2.3 Polyesters and Polyamides

Practice questions covering the formation, properties, and hydrolysis of polyesters, polyamides, and polypeptides based on A-level chemistry notes.

What is the definition of condensation polymerisation?

The joining of bifunctional monomers with the elimination of a small molecule such as $H_2O$ or $HCl$.

What are two common types of materials formed by condensation polymerisation?

Polyesters (such as terylene) and polyamides (such as nylon).

Which monomers are used to synthesize the polyester Terylene (PET)?

Ethan-1,2-diol and benzene-1,4-dioic acid.

By what type of linkage are the monomers in polyesters joined?

An ester linkage.

Which monomers are polymerised to create Nylon?

1,6-diaminohexane and hexane-1,6-dioic acid.

What small molecule is lost during the polymerisation of 1,6-diaminohexane and hexane-1,6-dioic acid to form nylon?

A water ($H_2O$) molecule.

What are the remarkable properties and uses of Kevlar?

Kevlar is fire resistant and has a higher strength than steel. It is used for protective clothing for fire fighters, bulletproof vests, and crash helmets.

Which two monomers form Kevlar?

Benzene-1,4-diamine and benzene-1,4-dioic acid.

What type of polyamide is formed by the polymerisation of amino acids?

Polypeptides.

How do addition polymers typically form in terms of chemical bonding?

They form when a $\pi$ bond in an alkene is broken and two new $\sigma$ bonds are formed, creating a long chain of continuous carbon atoms.

Why are condensation polymers generally biodegradable?

They can undergo acid or base hydrolysis of the ester or amide bonds.

Contrast the biodegradability of addition polymers with condensation polymers.

Addition polymers are generally not biodegradable as they withstand hydrolysis, whereas condensation polymers are generally biodegradable through hydrolysis.

What is the common name for 2-hydroxypropanoic acid?

Lactic acid.

What are the monomers required to form polylactic acid?

2-hydroxypropanoic acid (lactic acid).

What are the catalysts used for the hydrolysis of polyesters and polyamides?

Acid hydrolysis typically uses $H^+/H_2O$ (e.g., $HCl/H_2O$) and base hydrolysis typically uses $NaOH/H_2O$ or $KOH/H_2O$.