How Addition Polymerisation Works at the Molecular Level
Part of Polymers — GCSE Chemistry
This how it works covers How Addition Polymerisation Works at the Molecular Level within Polymers for GCSE Chemistry. Revise Polymers in Organic Chemistry for GCSE Chemistry with 20 exam-style questions and 14 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 5 of 15 in this topic. Use this how it works to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 5 of 15
Practice
20 questions
Recall
14 flashcards
⚙️ How Addition Polymerisation Works at the Molecular Level
Addition polymerisation works because alkene double bonds can "open up" when activated by a catalyst or high temperature and pressure. Here's the step-by-step process:
- The C=C double bond in each alkene monomer consists of a sigma bond and a weaker pi bond
- Under the right conditions, the pi bond breaks, leaving each carbon with an unpaired electron (a free radical or active site)
- These reactive carbons bond to adjacent monomers — one bond connects to the monomer behind, one to the monomer ahead
- This process repeats thousands of times, building up a long polymer chain
- The result: every carbon in the chain now has only single bonds — the polymer is saturated even though the monomer was unsaturated
Key facts about the reaction:
- Only one product forms — the polymer (no small molecule by-product)
- Monomers must be alkenes (contain C=C)
- The polymer repeating unit has the same atoms as the monomer, just rearranged (all single bonds)
- Conditions: high temperature, high pressure, and often a catalyst