4.1.3 Polymers
🧪 What are Polymers?
Polymers are extremely large molecules made of repeating monomer units.
The Mayan civilisation was one of the first to use natural polymers (e.g., rubber).
Synthetic polymers (e.g., Bakelite) were first developed in 1907 and became widely produced in the late 1920s (e.g., PVC).
📌 Key Terms:
Monomer → Small molecules that join to form polymers.
Polymer → Large molecules made of many repeating monomer units.
Addition Polymerisation → The process where monomers with C=C double bonds react to form a long saturated polymer chain.
🔗 Addition Polymerisation
✅ Alkenes undergo addition polymerisation to form long saturated polymer chains.
✅ This process occurs at high temperature and high pressure using catalysts.
📌 Properties of Addition Polymers:
High molecular mass
Named after the monomer (e.g., ethene → poly(ethene))
Repeat units written in square brackets
Letter 'n' shows many repeating units
📌 General Equation:
Monomer (C=C) → Polymer (long saturated chain)
🧪 Poly(ethene) – A Common Addition Polymer
Made by heating ethene at high pressure.
Most widely used polymer (e.g., bags, bottles, toys, straws).
📌 Two Types:
High-Density Poly(ethene) (HDPE) → Linear chains, stronger, used in bottles & pipes.
Low-Density Poly(ethene) (LDPE) → Branched chains, flexible, used in plastic bags.
Poly (chloroethene) A.K.A poly (vinyl chloride) or PVC
PVC is known for its flexibility and rigidity, which leads to a variety of uses👇
Other Polymers and their Monomers
Poly(propene)
Don't fall in the classic trap of drawing three carbons in a row to repeat unit of this polymer.
Used to make children's toys, crates, fibre for ropes and guttering.
Poly(phenylethene) A.K.A Poly(styrene)
The hexagon attached to the carbon in phenylethene is a benzene ring, which, when part of a larger molecule, is referred to as a phenyl group.
Used for packaging materials, and food trays and cups. It is made of up to 95% air, so it is an amazing insulator.
Poly(tetrafluoroethene) A.K.A Teflon
the tetrafluoroethen monomer
TEFLON is used as a coating for non-stick frying pans.
🔬 Identifying Monomers from Polymers
To find the monomer from a polymer:
Identify the repeat unit.
Break a single C–C bond into a C=C double bond.
🌍 Environmental Concerns
🚮 Disposal of Waste Polymers
Polymers are non-biodegradable, leading to plastic pollution.
Waste plastics harm marine life.
🔄 Recycling Polymers
Reduces landfill & conserves fossil fuels.
Sorting is necessary to avoid contamination.
PVC recycling is difficult due to toxic chlorine-containing additives.
🔥 Using Polymers as Fuel
Some waste polymers are burned to generate energy.
Incineration must be controlled to reduce harmful emissions.
🧪 Biodegradable & Photodegradable Polymers
🌱 Biodegradable Polymers
Broken down by microorganisms into water, CO₂, & biomass.
Often made from starch or cellulose.
Example: Polylactic acid (PLA) → Used in compostable supermarket bags.
☀️ Photodegradable Polymers
Contain bonds that break in sunlight.
Used in packaging & agricultural films.
Want to find out more about Bioplastics? Click here to read my hidden blog about whether they can actually make a difference.
Sugar cane is used as a starting material for bioplastics