ChemistryChapter 12: Polymers
12.1.1 Addition Polymers
**Addition Polymers:** Addition polymers are formed by adding monomer units without losing small molecules
Explanation level
Introduction
Addition polymers are a major class of polymers formed by the addition of monomer units without losing any small molecules. The monomers used in addition polymerisation usually contain double or triple bonds, which open up and combine to form long polymer chains.
This section explains what addition polymers are, how they are formed, and provides important examples.
Definition
Addition Polymers: Addition polymers are formed by adding monomer units without losing small molecules.
In simple words: Addition polymers are made when monomers with double bonds join together in a long chain without releasing any small molecule.
Main Idea
- Addition polymers are formed by adding monomer units without losing small molecules.
- Monomers usually contain double or triple bonds that open and combine to form a polymer.
- The number of carbon atoms in these chains can vary from 4000 to 40,000.
- The repeating unit of an addition polymer is the same as the monomer, except that the double bond is replaced by a single bond after polymerisation.
- Examples:
Core Concept
| Feature | Description |
|---|---|
| Formation | Adding monomer units without losing small molecules |
| Monomers | Contain double or triple bonds |
| Repeating unit | Same as monomer, but with single bonds |
| Chain length | 4000 to 40,000 carbon atoms |
| Examples | Polyethene, Polypropylene, PVC |
Key point: Addition polymers are formed by the addition of monomers with double or triple bonds, without losing any small molecules.
Detailed Explanation
What are Addition Polymers?
Addition polymers are formed by adding monomer units without losing the small molecules.
- Monomers usually contain double or triple bonds that open and combine to form a polymer.
- The number of carbon atoms in these chains can vary from 4000 to 40,000.
Key point: Addition polymers are formed by the addition of monomers with double or triple bonds.
Example 1: Polyethene (PE)
What it is: Ethene is the smallest hydrocarbon containing a carbon-carbon double bond. Ethene molecules can join together to produce very long chains.
How it forms:
- Part of the double bond is broken, and the electrons in it are used to join neighbouring molecules.
- This process is called addition polymerisation.
- At high temperatures and high pressures, the monomer ethene joins up to give a polymer called polyethylene or polyethene.
Equation:
n\ CH2 = CH2 → (-CH2 - CH2 -)n
Monomer: CH2 = CH2 (ethene)
Repeating unit: -CH2 - CH2 -
Key point: Polyethene is formed by the addition polymerisation of ethene.
Example 2: Polypropylene (PP)
What it is: Polypropylene (PP) consists of propylene monomer (CH2 = CH - CH3).
Equation:
n\ CH2 = CH - CH3 → (-CH2 - CH(CH3)-)n
Monomer: CH2 = CH - CH3 (propene)
Repeating unit: -CH2 - CH(CH3)-
Key point: Polypropylene is formed by the addition polymerisation of propene.
Example 3: Polyvinylchloride (PVC)
What it is: Chloroethene is an ethene molecule in which one of the hydrogen atoms is replaced by a chlorine atom. It is called vinyl chloride.
- Polymerising vinyl chloride gives polychloroethene.
- Its commercial name is polyvinylchloride (PVC).
Equation:
n\ CH2 = CHCl → (-CH2 - CHCl -)n
Monomer: CH2 = CHCl (vinyl chloride)
Repeating unit: -CH2 - CHCl -
Key point: PVC is formed by the addition polymerisation of vinyl chloride.
Summary Table
| Polymer | Monomer | Repeating Unit | Equation |
|---|---|---|---|
| Polyethene (PE) | CH2 = CH2 (ethene) | -CH2 - CH2 - | n\ CH2=CH2 → (-CH2-CH2-)n |
| Polypropylene (PP) | CH2 = CH - CH3 (propene) | -CH2 - CH(CH3)- | n\ CH2=CH-CH3 → (-CH2-CH(CH3)-)n |
| Polyvinylchloride (PVC) | CH2 = CHCl (vinyl chloride) | -CH2 - CHCl - | n\ CH2=CHCl → (-CH2-CHCl-)n |
Intermediate Level
Addition polymerisation:
- Monomers with double or triple bonds open up and combine to form a polymer.
- No small molecules are released.
- The repeating unit is the same as the monomer, but with single bonds.
Examples:
| Polymer | Monomer | Repeating Unit |
|---|---|---|
| Polyethene (PE) | CH2 = CH2 | -CH2 - CH2 - |
| Polypropylene (PP) | CH2 = CH - CH3 | -CH2 - CH(CH3)- |
| Polyvinylchloride (PVC) | CH2 = CHCl | -CH2 - CHCl - |
Key point: Addition polymers are formed by the addition of monomers with double or triple bonds, without losing any small molecules.
Solved Example
Example: Identify the Monomer and Repeating Unit of Polypropylene
Question: Identify the monomer and repeating unit of polypropylene.
Solution:
Monomer: CH2 = CH - CH3 (propene)
Repeating unit: -CH2 - CH(CH3)-
Final Answer: Monomer: CH2 = CH - CH3; Repeating unit: -CH2 - CH(CH3)-
Example: Write the Equation for the Formation of PVC
Question: Write the equation for the formation of polyvinylchloride (PVC) from its monomer.
Solution:
Monomer: CH2 = CHCl (vinyl chloride)
Equation:
n\ CH2 = CHCl → (-CH2 - CHCl -)n
Final Answer: n\ CH2 = CHCl → (-CH2 - CHCl -)n
Important Points
- - Addition polymers = formed by adding monomer units without losing small molecules.
- - Monomers usually contain double or triple bonds.
- - The number of carbon atoms in these chains can vary from 4000 to 40,000.
- - The repeating unit is the same as the monomer, except that the double bond is replaced by a single bond.
- - Examples:
- 1. Polyethene (PE) — from ethene (CH2 = CH2)
- 2. Polypropylene (PP) — from propene (CH2 = CH - CH3)
- 3. Polyvinylchloride (PVC) — from vinyl chloride (CH2 = CHCl)
- - Equations:
- - n\ CH2=CH2 → (-CH2-CH2-)n
- - n\ CH2=CH-CH3 → (-CH2-CH(CH3)-)n
- - n\ CH2=CHCl → (-CH2-CHCl-)n
Remember
- - Addition polymers = formed by adding monomers without losing small molecules.
- - Monomers have double or triple bonds.
- - Repeating unit = same as monomer, but with single bonds.
- - Examples:
- - Polyethene (PE) — from ethene
- - Polypropylene (PP) — from propene
- - Polyvinylchloride (PVC) — from vinyl chloride
- - Equations:
- - n\ CH2=CH2 → (-CH2-CH2-)n
- - n\ CH2=CH-CH3 → (-CH2-CH(CH3)-)n
- - n\ CH2=CHCl → (-CH2-CHCl-)n
Common Mistakes
| Mistake | Correction |
|---|---|
| Thinking addition polymers release small molecules | Addition polymers do not release small molecules |
| Forgetting that monomers have double or triple bonds | Monomers in addition polymerisation have double or triple bonds |
| Confusing the repeating unit with the monomer | The repeating unit is the same as the monomer, but with single bonds |
| Thinking polyethene is made from ethane | Polyethene is made from ethene (CH2=CH2) |
| Thinking polypropylene is made from propane | Polypropylene is made from propene (CH2=CH-CH3) |
| Thinking PVC is made from ethane | PVC is made from vinyl chloride (CH2=CHCl) |
| Forgetting that addition polymers are formed at high temperature and pressure | Polyethene is formed at high temperature and pressure |
Quick Revision
Addition Polymers:
Addition polymers are formed by adding monomer units without losing the small molecules. Monomers usually contain double or triple bonds that open and combine to form a polymer. The number of carbon atoms in these chains can vary from 4000 to 40,000. For example; Ethene is the smallest hydrocarbon containing a carbon-carbon double bond. Ethene molecules can join together to produce very long chains. Part of the double bond is broken, and the electrons in it are used to join neighbouring molecules. This process is called addition polymerisation.
At high temperatures and high pressures, the monomer ethene joins up to give a polymer called polyethylene or polyethene.
- n\ CH2 = CH2 → (-CH2 - CH2 -)n
Repeating units: For a polymer, a repeating unit is the same as a monomer, except that the double bond is replaced by a single bond after polymerization.
Repeating unit: -CH2 - CH2 -
Polyethylene (PE) consists of ethylene monomer (CH2 = CH2)
Monomer: CH2 = CH2
For example, Polypropylene (PP) consists of propylene monomer (CH2 = CH - CH3)
Monomer: CH2 = CH - CH3
Repeating unit: -CH2 - CH(CH3)-
Example: Polyvinylchloride consists of vinyl chloride monomer (CH2 = CHCl)
Chloroethene is an ethene molecule in which one of the hydrogen atoms is replaced by a chlorine atom. It is called vinyl chloride. Polymerising vinyl chloride gives polychloroethene. Its commercial name is polyvinylchloride (PVC).
- n\ CH2 = CHCl → (-CH2 - CHCl -)n
60-Second Revision
- Addition polymers = formed by adding monomers without losing small molecules.
- Monomers have double or triple bonds.
- Repeating unit = same as monomer, but with single bonds.
- Examples:
- Polyethene (PE) — from ethene
- Polypropylene (PP) — from propene
- Polyvinylchloride (PVC) — from vinyl chloride
- Equations:
- n\ CH2=CH2 → (-CH2-CH2-)n
- n\ CH2=CH-CH3 → (-CH2-CH(CH3)-)n
- n\ CH2=CHCl → (-CH2-CHCl-)n
- Chain length: 4000 to 40,000 carbon atoms.
- No small molecule released.
- ⚠️ Warning: addition polymers do not release any small molecule, unlike condensation polymers.
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Quick revision
Revision Zone
Review the key facts, formulas and checks before you move on.12.1.1 Addition Polymers
Sticky Notes · Quick Revision
Key Point 1
- Addition polymers = formed by adding monomers without losing small molecules.
Key Point 2
- Monomers have double or triple bonds.
Key Point 3
- Repeating unit = same as monomer, but with single bonds.
Key Point 4
- Examples:
Key Point 5
- Polyethene (PE) — from ethene
Key Point 6
- Polypropylene (PP) — from propene
Key Point 7
- Polyvinylchloride (PVC) — from vinyl chloride
Key Point 8
- Equations:
Key Point 9
- n\ CH2=CH2 → (-CH2-CH2-)n
Key Point 10
- n\ CH2=CH-CH3 → (-CH2-CH(CH3)-)n
Key Point 11
- n\ CH2=CHCl → (-CH2-CHCl-)n
Key Point 12
- Chain length: 4000 to 40,000 carbon atoms.
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