What Are Polymers?
The word ‘Polymer’ is of Greek origin. ‘Poly’ means many and ‘mer’ means basic smaller unit. Polymers are very long chains made of repeating smaller molecules called ‘monomers’ that are joined together by covalent bonds and the process is called polymerization. The diagram below shows how repeating monomers join to form a polymer:
Polyvinyl Chloride (PVC) is a common plastic used for water pipes. The monomer and polymers of PVC is shown below.
Compare the following things. Ice cubes and a polythene bag. In both the materials, there are large number molecules combined together. Are both polymers?
Polymers can be classified into natural and synthetic polymers. Can you imagine that your body produces and you are made up of natural polymers? The most familiar polymers that we use in our daily life are man-made and synthetic.
Natural polymers are found in living systems that include proteins and carbohydrates in our bodies and cellulose in wood and paper. They play a very important role in living things to provide structural materials and molecules needed for life processes.
Protein polymers are made from amino acid monomers (20 different kinds of amino acids). Different combinations of the amino acid monomers create many different protein polymers. Examples of protein polymers include DNA, enzymes, silk, skin, hair, fingernails, feathers and fur.
Examples of carbohydrate polymers include cellulose, chitin and lignin found in plants. Cellulose is made of sugar molecules and is the main component of cotton used in clothing. Chitin is found in the cell walls of fungi such as mushrooms and exoskeletons of insects such as crabs and spiders. Lignin consists of a network of polymers and is important in giving structure to plants.
Synthetic polymers are man-made polymers produced by using raw materials from petroleum oil and gas. Plastics are synthetic polymers. When oils and gases are processed to make petrol, ethylene and propylene monomers are removed as by- products. We have already seen that polymer such as the Poly Vinyl Chloride (PVC) is made up of many monomers joined together. Ethylene and propylene are the building block monomers that make up many different types of plastics.
Based on the nature of the monomers, the way they are arranged in the polymer and the characteristics of final polymer.
There are grouped into different categories such as fibres, plastics, proteins. Let us study about few of them in the following sections.