Natural polymer

A natural polymer is a polymer that occurs in living things rather than being manufactured. The examples the exam expects are natural rubber, protein, starch, cellulose, silk and wool. Malay: polimer semula jadi · Chinese: 天然聚合物.

Each natural polymer is still built the same way as any polymer, from many small monomers joined into long chains, but the monomers come from biological sources. Natural rubber is poly(isoprene), made of many isoprene units; protein is made of many amino acids joined by condensation; and starch and cellulose are both made of many glucose units. Learning the monomer that matches each natural polymer is a favourite short-answer question, so it pays to memorise the pairs: rubber–isoprene, protein–amino acid, starch and cellulose–glucose.

Example. Natural rubber tapped from the rubber tree is a natural polymer. Its latex carries long poly(isoprene) chains, each formed from thousands of isoprene monomer units, which is why rubber stretches and returns to shape.

Confusion to avoid. Do not mix up natural polymers with synthetic polymers. A natural polymer forms in living things, while a synthetic polymer is manufactured in industry, usually from petroleum. Natural rubber is natural; polythene, PVC and nylon are synthetic. Being “natural” does not make a material simple, these are still large, complex macromolecules.

In everyday terms, the clothes, food and materials around us are full of natural polymers: cotton and paper are cellulose, wool and silk are proteins, and the elastic in a rubber band is poly(isoprene). Seeing these familiar examples helps you remember that a polymer need not be a plastic at all, and that the same joining of monomers underlies both the living and the manufactured world.

Natural polymers open the chapter by showing that polymers are not only man-made plastics but also the materials of life, connecting directly to natural rubber and to the monomers isoprene, amino acid and glucose that reappear throughout SPM Chemistry.