Definition and Formation
Definition of Polymers: Polymers are very large molecules, also called macromolecules, that are made when lots of smaller molecules, called monomers, join together in a chain. This process of joining makes the polymer strong and useful for many things.
Monomers as Building Blocks: Monomers are tiny, repeating molecules that are like building blocks. When they join together using strong chemical bonds called covalent bonds, they create a long chain called a polymer. These chains can be straight or branched, depending on the monomers and how they connect.
Polymerisation Process: Polymerisation is the special name for the process where monomers chemically react and connect to form a polymer. This is how many useful materials like plastics and rubbers are made.
Classification of Polymers Based on Source
Natural Polymers
Derived from Organisms: Natural polymers are made by living things like plants and animals. They are found in nature without needing to be made in a lab.
Starch: Starch is a natural polymer made when many glucose (sugar) molecules join together. It is stored in plants and used by them to save energy for later.
Protein: Proteins are polymers made from building blocks called amino acids. These are important for building muscles, enzymes, and other parts of living organisms.
Fat: Fats are made by joining a molecule called glycerol to three fatty acids. They are used by animals and humans to store energy and keep the body warm.
Natural Rubber: Natural rubber is made from a molecule called isoprene. It comes from the sap of rubber trees and is stretchy, which makes it great for making things like elastic bands.
Cellulose: Cellulose is a strong natural polymer made from glucose molecules. It helps give structure to plant cell walls, making plants firm and upright.
Nucleic Acids: DNA and RNA are natural polymers called nucleic acids. They are made of small parts called nucleotides and store instructions for how living things grow and function.
Synthetic Polymers
Man-Made Origins: Synthetic polymers are not found in nature. Instead, scientists make them in factories, usually using chemicals from oil or petroleum.
Polyethene (PE): Polyethene is made from a gas called ethene. It is light, cheap, and is used to make plastic bags, bottles, and food wraps.
Polypropene: This polymer is made from a gas called propene. It is strong and used in things like plastic ropes, food containers, and car parts.
Polyvinyl Chloride (PVC): PVC is made from a chemical called vinyl chloride. It is tough and waterproof, so it is good for making water pipes and electrical cables.
Polystyrene: This is made from a monomer called styrene. It is often used for making foam packaging, plastic cutlery, and disposable cups.
Perspex (PMMA): Perspex is made from methyl methacrylate. It is a clear plastic that looks like glass and is used in windows, signs, and display screens.
Polyester (Terylene): Polyester is made from chemicals called esters. It is commonly used to make fabric for clothes and curtains because it is strong and dries quickly.
Nylon: Nylon is made when two types of monomers (containing amide groups) join together. It is used in textiles, toothbrushes, and parachutes because it is strong and flexible.
Classification of Polymers Based on Properties
Thermoplastics
Heat-Reshapable: Thermoplastics can be heated and softened many times. When warm, they become bendy and can be reshaped, which is useful for recycling.
Linear Chains: Thermoplastics have straight or slightly branched chains of molecules. These chains slide over each other when heated, allowing the material to be reshaped.
Examples of Thermoplastics: Common examples include polyethene (used in plastic bags), polypropene (used in food containers), PVC (used in pipes), and polystyrene (used in packaging).
Thermosets
Permanently Hard: Thermoset polymers become hard when heated, and once they set, they cannot be melted again. They are used for things that must stay strong under heat.
Cross-Linking Chains: In thermosets, heating makes the polymer chains form strong links between them. These are called cross-links and make the material very hard.
Rigid Structure: Because of these cross-links, thermosets have a stiff and tough structure. They don’t bend or melt when heated.
Examples of Thermosets: Examples include Bakelite (used in electrical fittings), melamine (used in plates), epoxy resins (used in adhesives), and polyurethanes (used in foam cushions).
Elastomers
Elastic Properties: Elastomers are special polymers that can be stretched and then return to their original shape, like a rubber band.
Loosely Linked Chains: Their polymer chains are linked loosely, which lets them move and stretch when pulled but return to shape afterward.
Examples of Elastomers: Examples include natural rubber, neoprene (used in wetsuits), and styrene-butadiene rubber (used in car tires).
Polymerisation Processes
Addition Polymerisation
Double Bond Addition: In addition polymerisation, monomers that have double bonds between carbon atoms (like C=C) join together. No other substances are produced during the reaction.
Bond Conversion: When these monomers join, their double bonds break and form single bonds, linking together to make a long polymer chain.
Examples of Addition Polymers: Examples include polyethene, polypropene, and PVC—all made without losing any small molecules.
Condensation Polymerisation
By-Product Elimination: In condensation polymerisation, monomers link together, but each time they do, they release a small molecule like water or hydrogen chloride (HCl) as a by-product.
Bond Formation: This process forms new bonds between monomers while removing small molecules. This helps create a strong, long polymer chain.
Examples of Condensation Polymers: Examples include nylon (used in clothing) and terylene (used in fabrics).
Uses of Polymers
Packaging Materials: Polymers are often used to make packaging because they are light, cheap, flexible, and strong. They help keep food and other products safe.
Bottles Manufacturing: Plastics like PET (polyethylene terephthalate) and HDPE (high-density polyethene) are used to make drink bottles because they are strong and do not react with liquids.
Pipes Production: Materials like PVC and polypropene are used for making pipes because they don’t rust, can last a long time, and are strong enough to carry water.
Clothing and Textiles: Polymers like polyester and nylon are popular in clothing because they are strong, elastic, and don’t wrinkle easily.
Diverse Applications: Polymers are also used in many other areas such as in paints (coatings), glues (adhesives), car parts, electronic gadgets, and medical tools like syringes and gloves.