Polymerisation Reactions

Addition Polymers

What is addition polymerisation?

A reaction in which many small alkene molecules join together to form a long-chain polymer.

What type of compounds undergo addition polymerisation?

Compounds containing a C=C double bond, especially alkenes.

Why can alkenes undergo addition polymerisation?

The C=C double bonds can open, allowing many alkene molecules to join together.

What happens to the C=C double bond during addition polymerisation?

The double bond opens and becomes C–C single bonds linking the monomers together.

What is a monomer?

A small molecule that can combine with many other monomer molecules to form a polymer.

What is a polymer?

A large long-chain molecule formed from many repeating monomer units.

What is a repeat unit?

The set of atoms that is repeated many times to produce the polymer structure.

What conditions are normally used for addition polymerisation?

High pressure and high temperature, with the exact conditions depending on the polymer.

How are addition polymers named?

Write poly followed by the name of the monomer in brackets.

What polymer is formed from ethene?

Poly(ethene), commonly called polythene.

What polymer is formed from propene?

Poly(propene), also called polypropylene.

What polymer is formed from chloroethene?

Poly(chloroethene), commonly called polyvinyl chloride (PVC).

What polymer is formed from tetrafluoroethene?

Poly(tetrafluoroethene), commonly called PTFE or Teflon.

What polymer is formed from phenylethene?

Poly(phenylethene), commonly called polystyrene.

What does the letter n represent in a polymerisation equation?

The number of monomer molecules that react and therefore the number of repeat units.

Why do polymers not have a fixed molecular formula?

Different polymer molecules can contain different numbers of repeat units.

How is a repeat unit shown in a polymer structure?

Inside square or curved brackets with an n outside the brackets.

What must be shown passing through the brackets of a polymer repeat unit?

Covalent bonds extending from both sides of the repeat unit.

Why are bonds shown passing through the brackets?

They show that the repeat unit is bonded to additional repeat units on each side.

What is the general change in addition polymerisation?

n C=C monomers → a polymer containing a C–C backbone.

What is the equation for polymerisation of ethene?

n CH₂=CH₂ → [–CH₂–CH₂–]ₙ.

What is the repeat unit of poly(ethene)?

[–CH₂–CH₂–]ₙ.

What is the equation for polymerisation of propene?

n CH₂=CHCH₃ → [–CH₂–CH(CH₃)–]ₙ.

What is the repeat unit of poly(propene)?

[–CH₂–CH(CH₃)–]ₙ.

What is the equation for polymerisation of chloroethene?

n CH₂=CHCl → [–CH₂–CHCl–]ₙ.

What is the repeat unit of PVC?

[–CH₂–CHCl–]ₙ.

What is the monomer used to make PVC?

Chloroethene.

What is the monomer used to make polystyrene?

Phenylethene.

What is the monomer used to make PTFE?

Tetrafluoroethene.

What is the monomer used to make polypropylene?

Propene.

How can you draw the repeat unit when given an alkene monomer?

Change the C=C double bond to a C–C single bond, keep all attached groups in the same positions, put the unit in brackets and add n.

Do atoms get removed when an alkene undergoes addition polymerisation?

No. All atoms from the monomers are retained in the polymer.

Are any small molecules produced during addition polymerisation?

No.

Is an addition polymer saturated or unsaturated?

Saturated, because the C=C double bonds in the monomers become C–C single bonds.

How can you identify the monomer from an addition polymer?

Find the two-carbon repeat unit and change the C–C single bond between those carbons into a C=C double bond.

What happens to the groups attached to the carbon backbone when identifying the monomer?

They remain attached to the same carbon atoms.

What feature must the monomer reconstructed from an addition polymer contain?

A C=C double bond.

How many carbon atoms from the alkene double bond form one repeat unit?

Two carbon atoms.

What should you look for first when identifying a monomer from a polymer chain?

The repeating two-carbon section of the polymer backbone.

What is the relationship between a monomer and a repeat unit in addition polymerisation?

The atoms in one monomer become one repeat unit of the polymer.

Why is addition polymerisation described as an addition reaction?

Monomer molecules add together without the elimination of any small molecules.