Polyamide

A polyamide is a condensation polymer whose chains are held together by amide links (–CONH–). It is typically made from a diamine (two –NH₂ groups) and a dicarboxylic acid (two –COOH groups), which join and release water. Malay: poliamida · Chinese: 聚酰胺.

The amide link forms when an amino group (–NH₂) reacts with a carboxyl group (–COOH), giving off a water molecule. Because each monomer has two reactive ends, the chain builds up in both directions into a long, strong molecule. The most important polyamide in the syllabus is nylon, whose strength and elasticity make it useful for ropes, fishing lines, parachutes and clothing. Proteins are natural polyamides, because the peptide bond joining amino acids is itself an amide link.

Example. Nylon is manufactured by the condensation polymerisation of a diamine with a dicarboxylic acid: the –NH₂ and –COOH groups react to build a long chain joined by amide links, releasing a water molecule at each join, and the polymer is drawn into strong fibres.

Confusion to avoid. Do not confuse a polyamide with a polyester. Both are condensation polymers, but a polyamide is joined by amide links (–CONH–) from a diamine and a diacid, while a polyester is joined by ester links (–COO–) from a diol and a diacid. Reading the linking group tells you which polymer you have.

A quick way to recognise a polyamide is the –CONH– group repeating along the backbone, the same amide link that biologists call a peptide bond in proteins. Questions often show two monomers and ask you to draw the link that forms and name the by-product, which for a polyamide is again water; keeping this parallel with polyester clear is what earns full marks.

Because nylon and protein are both polyamides, this term bridges manufactured materials and the chemistry of life, and it reliably appears in condensation-polymerisation questions in SPM Chemistry.