Polymers

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Notes

Polymers: The Basics

**Polymers** are large molecules made from many smaller **monomers** joined by **covalent bonds**.
Examples: **poly(ethene)**, **PVC**, **nylon**.
Monomers are the repeating units that link to form the polymer chain.

Addition Polymerisation

**Addition polymerisation** joins monomers containing a **C=C double bond** (alkenes).
The C=C bond breaks, monomers add together, forming a long chain with only **single bonds**.
Only **one product** is formed – the polymer itself.
Example: ethene → poly(ethene).
Polymer name: **poly(monomer name)**, e.g., propene → **poly(propene)**.
To draw a repeat unit: change C=C to C–C, add continuation bonds, and write subscript **n**.

Deducing Monomer from Polymer (Addition)

Identify the **repeat unit** in the polymer chain.
Change the single bond between repeat units to a **double bond**.
Remove the continuation bonds to reveal the monomer structure.

Condensation Polymerisation

**Condensation polymerisation** links two different monomers with the removal of a **small molecule** (usually **water**).
Monomers have **two functional groups** (one at each end).
Forms the polymer **plus one water molecule per linkage**.
Examples: **nylon** (polyamide) and **PET** (polyester).

Nylon – A Polyamide

Nylon is made from a **dicarboxylic acid** (–COOH at both ends) and a **diamine** (–NH₂ at both ends).
Reaction forms an **amide linkage** (–CO–NH–) and releases water.
Represented by boxes for carbon chains with amide links alternating.

PET – A Polyester

PET (polyethylene terephthalate) is made from a **dicarboxylic acid** and a **diol** (–OH at both ends).
Reaction forms an **ester linkage** (–COO–) and releases water.
Also known as **terylene**; used in plastic bottles and synthetic fibres.
Represented by boxes for carbon chains with ester links alternating.

Plastics & Their Disposal

Many polymers are **non-biodegradable** – not broken down by microorganisms.
**Incineration**: releases CO₂ (greenhouse gas), may produce toxic fumes (e.g., HCl from PVC) or CO if incomplete.
**Landfills**: take up valuable land; non-biodegradable plastics accumulate.
**Ocean pollution**: plastic waste harms marine life.
**PET recycling**: can be depolymerised by **enzymes** or **chemical catalysts** under mild conditions, then re-polymerised – saves resources and energy.

Proteins – Natural Polyamides

Proteins are **condensation polymers** of **amino acid** monomers.
Amino acids have both –NH₂ and –COOH groups; the amide link is called a **peptide link**.
Proteins are **natural polyamides**; there are 20 common amino acids with different R groups.
Represented by boxes for carbon chains with peptide links alternating.

Comparison of addition and condensation polymerisation with examples.

Environmental problems from polymer disposal and PET recycling.

Practice questions

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1.What is a polymer?
Easy
- AA large molecule made from many smaller molecules called monomers
- BA small molecule used to make larger molecules
- CA molecule containing only carbon and hydrogen
- DA molecule that contains a carbon-carbon double bond
2.Which type of polymerisation forms poly(ethene) from ethene?
Easy
- AAddition polymerisation
- BCondensation polymerisation
- CHydrolysis
- DCracking
3.What is a monomer?
Easy
- AA small molecule that can join with others to form a polymer
- BA large molecule made from repeating units
- CA type of polymer
- DA catalyst used in polymerisation
4.Which of the following is an example of a polymer?
Easy
- APoly(ethene)
- BEthene
- CCarbon dioxide
- DWater
5.What is the key difference between addition polymerisation and condensation polymerisation?
Medium
- ACondensation polymerisation produces a small molecule, such as water, as a by-product; addition polymerisation does not
- BAddition polymerisation produces a small molecule as a by-product; condensation polymerisation does not
- CAddition polymerisation requires a catalyst; condensation polymerisation does not
- DCondensation polymerisation only occurs with alkenes; addition polymerisation occurs with any monomer
6.Which of the following monomers can undergo addition polymerisation?
Medium
- AEthene
- BEthane
- CEthanol
- DEthanoic acid
7.What type of polymer is nylon?
Medium
- APolyamide
- BPolyester
- CPolyalkene
- DPolypeptide
8.What is the name of the linkage formed in polyesters?
Medium
- AEster linkage
- BAmide linkage
- CPeptide linkage
- DCovalent bond

Slides

Polymers: The Basics

Polymers are large molecules built up from many smaller molecules called monomers.
Each monomer is joined to the next by covalent bonds.
Examples of polymers include poly(ethene), PVC, and nylon.

What are the small molecules that join together to form polymers called?

Monomers
Isomers
Alkenes
Dimers

Addition Polymerisation

Addition polymerisation occurs when monomers containing a C=C double bond join together.
The C=C bond breaks, and monomers form single bonds to create a long-chain polymer.
Only one product is formed: the polymer itself.

In addition polymerisation, the ____ bond in each monomer breaks, and only ____ product is formed.

Deducing the Polymer from the Monomer

To draw a repeat unit: change the double bond to a single bond, add continuation bonds at each end, and put brackets around the unit with a subscript n.
The name of the polymer is 'poly(monomer name)', e.g., propene gives poly(propene).

Which of the following is the correct repeat unit for poly(ethene)?

-CH2-CH2-
-CH=CH-
-CH2-CH3-
-CH2-CH2-CH2-

Condensation Polymerisation

Condensation polymers form when two different monomers link together with the removal of a small molecule, usually water.
Each monomer has two functional groups (one at each end).
Examples: nylon (polyamide) and PET (polyester).

Which of these are true about condensation polymerisation?

A small molecule, usually water, is removed.
Only one product is formed.
Monomers must have two functional groups.

Nylon: A Polyamide

Nylon is made from a dicarboxylic acid (with -COOH groups at both ends) and a diamine (with -NH2 groups at both ends).
An amide linkage forms with the loss of one water molecule per link.
The structure can be represented with boxes for carbon chains and amide links.

Nylon is a ____ made from a dicarboxylic acid and a ____.

PET: A Polyester

PET (polyethylene terephthalate) is a polyester made from a dicarboxylic acid and a diol (alcohol with -OH groups at both ends).
An ester linkage forms with the loss of one water molecule per link.
PET is used for plastic bottles and synthetic fibres (terylene).

What small molecule is removed when an ester linkage forms in condensation polymerisation?

Water
Carbon dioxide
Hydrogen
Ammonia

Plastics and Their Disposal

Plastics are made from polymers; many are non-biodegradable (cannot be broken down by micro-organisms).
Disposal problems: incineration releases CO2 and toxic fumes (e.g., HCl from PVC), landfills take up space, and plastic pollutes oceans.
PET can be depolymerised using enzymes or chemical methods and then re-polymerised.

Which of these are problems caused by plastic disposal?

Landfills fill up quickly because polymers are non-biodegradable.
Burning polymers always produces only harmless gases.
Plastic waste in oceans harms marine life.

Proteins: Natural Polyamides

Proteins are condensation polymers made from amino acid monomers.
Amino acids contain NH2 and COOH functional groups.
The amide links in proteins are called peptide links.
Proteins can contain 60–600 amino acids in different orders.

Proteins are formed from ____ monomers joined by ____ links.

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