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Addition polymers
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Small alkene molecules join into very long chains called addition polymers. They are useful, but hard to dispose of.
Monomers and polymers
An addition polymer is made by joining many small molecules called monomers.
The monomers have a C=C double bond. The double bonds open and the monomers join in a long chain.
n CH2=CH2 → -(CH2-CH2)n- (ethene → poly(ethene))
The monomers have a C=C double bond. The double bonds open and the monomers join in a long chain.
n CH2=CH2 → -(CH2-CH2)n- (ethene → poly(ethene))
Repeat units
Monomer from repeat unit, and disposal
To get the monomer from a repeat unit, remove the brackets and the n, and put a C=C between the two carbons.
To get the repeat unit from the monomer, change C=C to C-C and draw bonds out through the brackets.
Disposal problems: addition polymers are inert and do not biodegrade, so they last for a very long time in landfill. Burning them can produce toxic gases (for example, PVC produces hydrogen chloride).
To get the repeat unit from the monomer, change C=C to C-C and draw bonds out through the brackets.
Disposal problems: addition polymers are inert and do not biodegrade, so they last for a very long time in landfill. Burning them can produce toxic gases (for example, PVC produces hydrogen chloride).
A repeat unit is -(CH2-CHCl)-. What is the monomer?
- Remove the brackets.
- Put a double bond between the two carbons.
Answer: Chloroethene, CH2=CHCl
Addition polymers form when many monomers with C=C join. Poly(ethene), poly(propene), poly(chloroethene) and PTFE. Put C=C back to find the monomer. Polymers are inert and non-biodegradable, and burning them can release toxic gases.
The interactive lesson includes the diagrams for this topic.
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