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Addition polymerization of alkenes. Connector - Draw the major addition products for the reactions between i) Br 2 & ii) HBr with: propene, but-1-ene, but-2-ene, and 2-methylpropene.

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slide1

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

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

Crowe2008

slide2

Br

H

Br

Br

H

Br

Br

Br

H

H

H

H

H

H

H

H

H

H

C – C C

C – C C

C C C C

C C C C

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

H

Markovnikov addition

Markovnikov addition

slide3

Br

H

H

Br

Br

Br

Br

Br

H

H

H

H

H

H

H

H

C C

C C

C C C C

C C C C

CH3

CH3

H

H

H

H

H

H

CH3

CH3

H

H

H

H

H

H

Markovnikov addition

monomers and polymers

Ethene

This molecule is called POLYETHENE, and the process that made it is called POLYMERISATION

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:

slide5

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 200°C
  • Pressure: about 2000 atmospheres
  • Initiator: a small amount of oxygen as an impurity
another way of drawing it

H

H

H

H

H

H

H

H

H

H

C

C

C

C

C

C

C

H

C

C

C

H

H

H

H

H

H

H

H

H

H

poly(e)thene

Pressure

high

temperature

catalyst

n

n

ethene

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

draw the equations for the polymerisation of the following alkenes and name the polymer

n

C

C

n

CH3

H

n

Poly(tetrafluoroethane)

or PTFE

tetrafluoroethene

H

H

Draw the equations for the polymerisation of the following alkenes and name the polymer:

propene

slide8

Poly(propene)

n

n

propene

n

n

Poly(tetrafluoroethene)

or PTFE

tetrafluoroethene

CH3

slide9

You may be asked to show polymerisation using three or more monomer units. e.g.

Draw a similar process for propene and chloroethene

thermosoftening polymers or thermoplastics
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

what are thermosetting plastics
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’).

homework research the problems and solutions wrst the use of polymers
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
slide14

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?

slide17

Life cycle analyses of three different materials for gas pipes

  • 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.
slide18

Life cycle analyses of three different materials for gas pipes

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