Polymers are giant molecules that make up many of the materials we use every day, from plastic bags to clothing and even the DNA in our cells. This guide explains what they are, how they are made, and highlights the most important examples for your exam.

1. The Basics: Monomers, Polymers, and Polymerization

Think of building a long chain with paper clips.

• Monomer: The single, small molecule that acts as the building block (one paper clip).

• Polymer: The large, long-chain molecule made by joining many monomers together (the whole chain of paper clips).

• Polymerization: The chemical process of joining monomers to form a polymer.

• Repeating Unit: The basic structural unit that repeats over and over in the polymer chain (the structure of a single paper clip within the chain).

2. Important Artificial Polymers (Plastics)

These are made by addition polymerization, where the double bond in the monomer breaks open to form single bonds with neighboring monomers.

a) Poly(ethene) or Polythene

• Monomer: Ethene

• Polymerization: Thousands of ethene molecules link up. n (Ethene molecules) → (Polythene chain)

• Uses: Plastic bags, bottles, toys, garbage bins.

b) Poly(chloroethene) or PVC (Polyvinyl Chloride)

• Monomer: Chloroethene (ethene with one hydrogen replaced by chlorine).

• Uses: Water pipes, gutters, electrical wire insulation, flexible pipes. It's known for being strong and weather-resistant.

c) Poly(tetrafluoroethene) or Teflon

• Monomer: Tetrafluoroethene (ethene with all four hydrogens replaced by fluorine).

• Uses: Non-stick coatings on cooking pans (it's very heat-resistant and slippery), making snowshoes.

3. Classifying Polymers

By Origin:

• Natural Polymers: Found in nature.

  • Examples: Rubber, Starch, Cellulose, Proteins, DNA.

• Synthetic (Artificial) Polymers: Man-made in factories.

  • Examples: Polythene, PVC, Nylon, Teflon.

By Structure:

• Linear Polymers: Simple, long chains (like Polythene).

• Branched Polymers: Have side chains branching off the main chain.

• Cross-linked Polymers: Linear chains are joined together by chemical bonds (cross-links), creating a strong network.

  • Key Example: Vulcanized Rubber. Natural rubber is soft and elastic. When it's heated with sulfur (vulcanization), sulfur atoms form cross-links between the rubber chains, making it much harder, stronger, and more durable. This is used to make car tires.

4. Environmental Impact

• The Problem: Most synthetic polymers (plastics) are non-biodegradable. This means they are not broken down by microorganisms and persist in the environment for hundreds of years, causing pollution.

• The Challenge: Burning them can release toxic gases. Therefore, waste management through the 4R method (Reduce, Reuse, Replace, Recycle) is crucial.

Exam Tips & Tricks

1. Know Your Monomers: You MUST be able to identify the monomer for the three main polymers: Polythene (monomer: ethene), PVC (monomer: chloroethene), and Teflon (monomer: tetrafluoroethene).

2. Drawing Repeating Units: A common question is to draw the repeating unit of a polymer. For addition polymers, simply change the monomer's double bond to a single bond and draw bonds extending outwards from the two carbon atoms.

3. Vulcanization: This is a very specific and important example of creating a cross-linked polymer. Remember that vulcanization involves heating rubber with sulfur to make it harder.

4. Natural vs. Synthetic: Be ready to give examples for each category. Don't forget that important biological molecules like starch and proteins are also polymers.