Polymerisation Addition Polymerisation Condensation Polymerisation Uses of polymers

Addition Polymerisation A carbon – carbon double bond is needed in the monomer A carbon – carbon double bond is needed in the monomer A monomer is the small molecule that makes up the polymer A monomer is the small molecule that makes up the polymer

Addition Polymerisation The polymer is the only product The polymer is the only product Involves the opening out of a double bond Involves the opening out of a double bond The conditions of the reaction can alter the properties of the polymer The conditions of the reaction can alter the properties of the polymer Reaction proceeds by a free radical mechanism Reaction proceeds by a free radical mechanism Oxygen often used as the initiator Oxygen often used as the initiator

Addition polymerisation The board specifies that you know this addition polymerisation reaction The board specifies that you know this addition polymerisation reaction

Addition polymerisation Conditions are high pressure and an oxygen initiator (to provide the initial free radical). Conditions are high pressure and an oxygen initiator (to provide the initial free radical). Monomer = phenylethene Monomer = phenylethene Polymer = poly(phenylethene) Polymer = poly(phenylethene)

Addition Polymerisation You are expected to be able to do the following things with addition polymers: You are expected to be able to do the following things with addition polymers: Predict the repeating unit of the polymer given the monomer Predict the repeating unit of the polymer given the monomer Predict the monomer from the polymer – displayed formula and even empirical formula. Predict the monomer from the polymer – displayed formula and even empirical formula. Know about stereochemistry of addition polymers. Know about stereochemistry of addition polymers.

Prediction the repeating unit This is easy, basically open out the double bond. This is easy, basically open out the double bond.

Predicting the monomer from the polymer This is kind of the opposite to what you have just done. This is kind of the opposite to what you have just done. They may ask you to draw different formulae. They may ask you to draw different formulae. You need to make sure you can convert repeating units into monomers, and draw a ring around the repeating unit You need to make sure you can convert repeating units into monomers, and draw a ring around the repeating unit

Stereoisomerism in Addition polymers. Ziegla and Natta in the 1950s cam up with a way of controlling the repeating unit. Ziegla and Natta in the 1950s cam up with a way of controlling the repeating unit. They won a Joint Nobel prize for their work They won a Joint Nobel prize for their work The polymerisation process can be controlled used a tin/aluminium catalyst at 50°C and 1.5atm The polymerisation process can be controlled used a tin/aluminium catalyst at 50°C and 1.5atm

Stereoisomerism in Addition polymers. Previous to this only one type of poly(ethene) could be made, called LDPE or low density poly(ethane). Previous to this only one type of poly(ethene) could be made, called LDPE or low density poly(ethane). The chains formed a tangled mass. The chains formed a tangled mass. HDPE could now be produced. HDPE could now be produced. This has a much stiffer structure due to areas of crytallinity where the polymer chains are much more ordered. This has a much stiffer structure due to areas of crytallinity where the polymer chains are much more ordered.

Stereoisomerism in Addition polymers. HDPE has a much higher boiling point due to these more ordered regions. HDPE has a much higher boiling point due to these more ordered regions. Generally used to make plastic bottles. Generally used to make plastic bottles. Ziegler and Natta also discovered that they could make stereo regular polymers. Isotactic, syndiotactic and atactic. Ziegler and Natta also discovered that they could make stereo regular polymers. Isotactic, syndiotactic and atactic.

Poly(propene) and stereoisomerism Isotactic. This is a very regular type of polymer chain. All the methyl groups are on the same side. Isotactic. This is a very regular type of polymer chain. All the methyl groups are on the same side.

Poly(propene) and stereoisomerism Syndiotactic. A slightly less regular but still very ordered polymer. Syndiotactic. A slightly less regular but still very ordered polymer. The methyl groups alternate the side of chain they are on. The methyl groups alternate the side of chain they are on.

Poly(propene) and stereoisomerism Atactic. Atactic. This is a completely random allocation of methyl groups along the carbon skeleton. This is a completely random allocation of methyl groups along the carbon skeleton.

Poly(propene) and stereoisomerism This varying degree of randomness will affect the strength and melting point of the polymer. This varying degree of randomness will affect the strength and melting point of the polymer. The less random, the stronger the polymer and the higher the melting point The less random, the stronger the polymer and the higher the melting point This is because in a more ordered polymer they chains can get closer together and hence the van der Waal’s forces will be greater. This is because in a more ordered polymer they chains can get closer together and hence the van der Waal’s forces will be greater.

Condensation Polymers Involves 2 monomers that have different functional groups. Involves 2 monomers that have different functional groups. They also involve the elimination of water or another small molecule. They also involve the elimination of water or another small molecule. Hence the term condensation polymer. Hence the term condensation polymer. Monomer A + Monomer B  Polymer + small molecule (normally water). Monomer A + Monomer B  Polymer + small molecule (normally water). Common condensation polymers include polyesters (the ester linkage) and polyamides (the amide linkage as in proteins). Common condensation polymers include polyesters (the ester linkage) and polyamides (the amide linkage as in proteins).

Polyesters The OCR example here is terylene, a polymer of benzene-1,4-dicarboxylic acid and ethane-1,2- diol. The OCR example here is terylene, a polymer of benzene-1,4-dicarboxylic acid and ethane-1,2- diol. The ester linkage is formed between the monomers The ester linkage is formed between the monomers

Polyesters You need to be able to reproduce the formation of terylene, and possibly predict the structures of other polyesters You need to be able to reproduce the formation of terylene, and possibly predict the structures of other polyesters

Polyamides These involve the linkage of two monomers through the amide linkage as in proteins (e.g. silk) These involve the linkage of two monomers through the amide linkage as in proteins (e.g. silk)

Nylon 6,6 a polyamide