Summary and Exam Tips for Addition polymerisation
Addition polymerisation is a subtopic of Polymerisation (AS-Level Organic Chemistry), which falls under the subject Chemistry in the Cambridge International A Levels curriculum. This type of polymerisation involves monomers with unsaturated bonds, such as alkenes, reacting to form a polymer chain without losing any atoms. Poly(ethene), or polyethylene, is a common example where ethene monomers polymerise through their double bonds, often initiated by a free radical like a peroxide, resulting in a chain of repeating units. Similarly, Poly(chloroethene), or PVC, is formed from vinyl chloride monomers, creating a chain with repeating units.
To deduce the repeat unit of an addition polymer, identify the monomer and understand the polymerisation mechanism. The repeat unit is the smallest repeating structure in the polymer chain. For instance, polyethylene's repeat unit is .
Disposal of polymers like poly(alkenes) poses environmental challenges due to their non-biodegradable nature and resistance to chemical attack. They persist in landfills for centuries and burning them releases toxic byproducts, contributing to pollution.
Exam Tips
- Understand the Mechanism: Focus on how monomers with unsaturated bonds form polymers without losing atoms. This is crucial for explaining addition polymerisation.
- Identify Repeat Units: Practice deducing repeat units from given monomers, such as for polyethylene, to strengthen your understanding.
- Environmental Impact: Be aware of the environmental issues related to polymer disposal, such as non-biodegradability and pollution from burning.
- Key Examples: Remember key examples like polyethylene and PVC, and their formation processes, as these are often tested.
- Free Radical Initiation: Understand the role of free radicals in initiating polymerisation, as this is a common exam question area.
