📘 IB Understanding
Addition polymerisation involves many small unsaturated monomer molecules (alkenes) joining together to form a long-chain polymer. No atoms are lost in the process and the atom economy is 100%.
The Process
The C=C double bonds of alkene monomers break open and link together, forming a chain of single C-C bonds. The only product is the polymer:
n CH2=CH2 → -(CH2-CH2)n-
Ethene to Poly(ethene)
Common Addition Polymers
| Monomer | Polymer | Uses |
|---|---|---|
| Ethene (CH2=CH2) | Poly(ethene) / polyethylene | Plastic bags, bottles |
| Propene (CH2=CHCH3) | Poly(propene) / polypropylene | Carpets, containers |
| Chloroethene (CH2=CHCl) | PVC | Pipes, flooring |
| Tetrafluoroethene (CF2=CF2) | PTFE (Teflon) | Non-stick pans |
| Styrene (C6H5CH=CH2) | Polystyrene | Packaging, insulation |
Environmental Impact
- Addition polymers are non-biodegradable because C-C backbones resist enzymatic breakdown
- They persist in landfills and oceans for hundreds of years
- Incineration produces CO2; PVC incineration can release toxic HCl
- Recycling reduces waste but requires sorting by polymer type
⚠️ Exam Tip
To draw for the repeat unit from the monomer: remove the double bond, add single bonds extending from each carbon, and enclose in brackets with subscript 'n'. To go from polymer to monomer: replace the brackets with a C=C double bond.