1. Chapter 18
Polymers
LEARNING OUTCOMES
Define polymers
Distinguish between addition and
condensation as reactions in the
formation of polymers
Show how the monomers are linked in
the structure of the polymer
Demonstrate the differences in
properties between the monomer and
the polymer it forms
2. Chapter 18
Polymers
LEARNING OUTCOMES
Name examples of polymers formed by addition reactions
Draw diagrams to represent the formulae of monomers
State at least one use of each of the following types of
polymers: polyalkene
Name examples of polymers formed by condensation
reactions
Draw diagrams to represent the formulae of compounds
State at least one use of each of the following types of
polymers: polyamide, polyester and polysaccharide
Describe the hydrolysis of proteins
Compare acid hydrolysis of a polysaccharide with
carbohydrate digestion in the body
3. Chapter 18
Polymers
Polymers
Polymers are very large molecules called macromolecules.
A macromolecule or polymer is built up of many small units called
monomers.
Different macromolecules or polymers have different units or
monomers joined by different linkages.
A polymer is a macromolecule which is made up of a large
number of simple molecules called monomers.
monomer monomer monomer monomer
polymer
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Polymers
Classifying Polymers
Polymers are either naturally occurring or synthetic.
Polymers are either addition polymers formed by an
addition process, or condensation polymers, formed
by the condensation process.
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Polymers
Polymerisation
Polymerisation is the process whereby two or more
simple molecules (monomers) react and link together to
form a much larger molecule called polymer.
There two types of polymerisation:
Addition polymerisation and
Condensation polymerisation.
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Polymers
Addition polymerisation
In addition polymerisation one monomer adds on to the
another monomer to form a long chain polymer.
The monomers must have a carbon-carbon double bond
so that addition reaction can take place.
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Polymers
Uses of polyethene
Polyethene is the most widely used form of plastics.
It is used for making common household
items like:
plastic bags
plastic bottles and containers
clingfilm for wrapping fish and vegetables
plastic buckets and hoses
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Polymers
Other addition polymers and their uses
Poly Vinyl Chloride (PVC)
It is an addition polymer made from a monomer called vinyl
chloride or chloroethene.
It is used for making water pipes, gloves, rain coats and
shower curtains.
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Polymers
Other addition polymers and their uses
Poly(tetrafluoroethene) [PTFE]
It is an addition polymer made from a monomer called
tetrafluoroethene.
F F
C=C
F F
It is used for making seals and washers and for coating
non-stick pots and pans.
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Polymers
Condensation Polymerisation
In condensation polymerisation, two or more monomers
join together with the elimination of a small molecule,
such as water.
The monomers must have different reactive functional
groups so that they can react together to form a polymer.
The polymer formed is called a condensation polymer.
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Polymers
Example of condensation polymerisation:
Nylon
Nylon is formed by condensation
polymerisation from a dicarboxylic
acid (hexanedioic acid) and a
diamine (1,6-diamino-hexane).
Uses of nlyon:
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Polymers
Terylene
Terylene is also a condensation polymer.
Terylene is formed by condensation
polymerisation from an diacid (benzene-
1,4-dicarboxylic acid) and a diol (ethane-
1,2-diol). = O
It is a polyester with a –C–O– linkage.
Uses of terylene:
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Polymers
Fats and Oils
Fats and oils are polyesters.
A fat molecule consists of two parts – glycerol and chains
of fatty acids.
Fats and oils contain three ester functional groups.
When fat is hydrolysed by an enzyme such as lipase,
glycerol and fatty acids are produced.
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Polymers
Test for Fats
1. Add 2 cm3 of ethanol to a sample of the unknown in a test
tube.
2. Shake the mixture thoroughly.
3. Add 2 cm3 of water.
If fat is present, a cloudy white suspension will form at the top of
the solution.
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Polymers
Polysaccharides
Polysaccharides are naturally occurring compounds with a general
formula CnH2nOn.
‘Mono’ means one and ‘saccharide’ means sugar.
Monosacharides are simple, single sugar molecules which comprise
only one single basic unit. E.g. glucose, fructose, galactose
Diasaccharides are complex sugars made up of two simple sugar
molecules. They are formed by condensation reactions. E.g. sucrose,
lactose, maltose
Polysaccharides are made up of a large number of monosaccharides
joined together by numerous condensation reactions. E.g. starch,
glycogen, cellulose
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Polymers
Test for Starch
1.Add a few drops of iodine solution to the unknown substance.
2.Observe the colour change, if any.
If starch is present, the iodine solution will turn from brown to blue-
black.
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Polymers
Test for Reducing Sugars – Benedict’s Test
1. Add 2 cm3 of Benedict’s solution to 2 cm3
of glucose solution or any other food
solution to be tested.
2. Shake the mixture and immerse the test
tube in a beaker of boiling water for two
minutes.
3. Observe and record any changes in
colour.
If reducing sugar is present, a brick red
ppt. (or green, yellow, or orange ppt.) is
formed. If no reducing sugar is present,
the solution remains blue in colour.
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Polymers
Plastics
Plastics are one of the most common materials
used in the world today.
It has wide applications in making a host of things
ranging from spectacles to aeroplane parts.
There are many kinds of plastics, such as:
Polyethene
Nylon
PVC
Polystyrene
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Polymers
Properties of plastics
Advantages
Light and durable
Corrosion resistant
Can be easily moulded into a wide variety
of shapes and sizes
Relatively cheap
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Polymers
Properties of plastics
Disadvantages
They burn easily to produce toxic fumes.
Most plastics are non-biodegradable,
(cannot be decomposed by air and
bacteria), and hence causes pollution
to the environment.
They are not as strong as metals.
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Polymers
Problems caused by the use of plastics
The use of plastics in society has increased at a tremendous rate.
We use twenty times more plastic than we did fifty years ago.
The manufacture of plastics uses up about 8% of the world’s oil
supply, leading to more competition for petroleum.
Since most plastics are non-biodegradable, the amount of plastic
waste accumulating is rapidly increasing in our environment.
Discarded plastics in rivers and oceans cause the death of many sea
creatures like turtles, fish and whales.
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Polymers
Some ways to reduce pollution
caused by plastics
1. Reduce the use of plastics for packaging and
transportation of goods.
2. Reduce the use of takeaway plastic bags when you
shop at supermarkets.
3. Practise and promote the use of proper disposal of
plastics used at home and on the beaches.
4. Reuse and recycle the used plastics.
29. Chapter 18
Polymers
Quick check
1. What is a polymer? Give two examples of polymers.
2. (a) State two reasons for using plastics in place of metals.
(b) Why is the body of a motor car not entirely
made of plastics?
3. (a) What is the difference between addition
polymerisation and condensation polymerisation?
(b) Give two examples each of addition polymers
and condensation polymers.
4. Deduce the structure of the monomers from which the following
polymers are built from.
(a) (b)
Solution
30. Chapter 18
Polymers
Solution to Quick Check
1. A polymer is a macromolecule made up of many small
units called monomers, e.g. nylon & Terylene.
2. (a) Plastics are lighter and easier to mould.
(b) Plastics are not strong enough to protect the
occupants in the car in case of accidents.
3. (a) In addition polymerisation, monomers are added
one to another to form a polymer, without any
molecule being removed from the reaction.
In condensation polymerisation, monomers are
joined together with the elimination of a small
molecule, such as water.
(b) Addition polymers: polyethene, polypropene
Condensation polymers: nylon, Terylene.
4. (a) (b)
Return
31. Chapter 18
Polymers
To learn more about Macromolecules and Plastics,
click on the links below!
1. http://en.wikipedia.org/wiki/Polymer
2. http://www.chemheritage.org/EducationalServices/nylon/chem/chem.html
3. http://www.chemguide.co.uk/organicprops/esters/polyesters.html
4. http://www.plasticsresource.com/s_plasticsresource/index.asp
5. http://www.sdplastics.com/plastics.html
