3g. describe the addition polymerization of alkenes and identify the repeat unit given the monomer, and vice versa

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3g. describe the addition polymerization
of alkenes and identify the repeat unit given the
monomer, and vice versa
Addition polymerization of alkenes
Connector - Draw the major addition products for
the reactions between i) Br2 ii) HBr
with propene, but-1-ene, but-2-ene, and
2-methylpropene

• Crowe2008

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Markovnikov addition
Markovnikov addition
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Markovnikov addition
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Monomers and Polymers
Ethene is called a MONOMER because it is just one
small molecule. We can use ethene to make
plastics
Step 1 Break the double bond
Step 2 Add lots of the molecules together
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• Manufacture of addition polymers.
• An addition reaction is one in which two or more
  molecules join together to give a single product.
  During the polymerisation of ethene, thousands of
  ethene molecules join together to make
  poly(ethene) - commonly called polythene.
• The number of molecules joining up is very
  variable, but is in the region of 2000 to 20000.
• Conditions
• Temperature about 200C
• Pressure about 2000 atmospheres
• Initiator a small amount of oxygen as an impurity

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Another way of drawing it
And lots more..
1 2 3 4
5 thousands
This is called addition polymerisation and is
written as
n a large number
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Draw the equations for the polymerisation of the
following alkenes and name the polymer
propene
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CH3
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You may be asked to show polymerisation using
three or more monomer units. e.g.
Draw a similar process for propene and
chloroethene
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Thermosoftening polymersor thermoplastics
These soften when heated and can be remoulded
into new shapes
weak intermolecular forces these let the chains
slide past each other
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What are thermosetting plastics?
Some polymer chains cannot slide past each other.
strong intermolecular forces(cross-links)
these hold the chains firmly in place
Plastics made of these polymers cannot be
stretched, are rigid and have a high melting
point. They are called thermosetting plastics (or
thermosets).
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Homework - Research the problems and solutions
wrst the use of polymers.

• You should include the following key areas
• Energy
• costs
• sources
• Resources used
• Disposal problems
• biodegradable polymers
• Carbon footprint
• Recycling/reusing

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Use the above data to compare the properties of
PLA with polystyrene and PVC. Produce graphs to
show the tensile strength, elastic modulus and
tear strength as both hard sheets and soft
films. How does PLA compare with conventional
polymers?
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How does PLA compare with conventional polymers?
hard sheets
soft films
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Life cycle analysis
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Life cycle analyses of three different materials
for gas pipes
cast iron polythene PVC
POCP 216 216 215
ECA 26 6.4 3.9
GWP 31 22 21
AP 13 2.5 1.1
ADP 9.7 1 0.45
HT 14 1.9 0.76
NP 2.5 0.61 0.33
OTL 11 0.39 0.48
ODP 1.25 0.17 0.07
EC 748 303 139

• Present the information in the form of a bar
  chart so that the environmental features may be
  compared.
• Suggest why the scientists may have been
  surprised by their findings.

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Life cycle analyses of three different materials
for gas pipes
cast iron polythene PVC

• Suggest why the scientists may have been
  surprised by their findings.