The Structure and Properties of Polymers

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Slide 1

The Structure and Properties of Polymers

Also known as

Bonding +

Properties

Slide 2

What is a polymer?

A long molecule made up from lots of small molecules called

monomers.

Slide 3

All the same monomer

Monomers all same type (A)

A + A + A + A 

-A-A-A-A-

eg poly(ethene) polychloroethene PVC

Slide 4

Different monomers

Monomers of two different types A + B

A + B + A + B

 -A-B-A-B-

eg polyamides

polyesters

Slide 5

Addition polymerisation

Monomers contain C=C bonds

Double bond opens to (link) bond to next monomer molecule

Chain forms when same basic unit is repeated over and over.

Modern polymers also developed based on alkynes R-C C - R’

Slide 6

Copolymerisation

when more than one monomer is used.

An irregular chain structure will result eg propene/ethene/propene/propene/ethene

Why might polymers designers want to design a polymer in this way?

(Hint) Intermolecular bonds!

Slide 7

Elastomers, plastics & fibres

Find a definition and suggest your own example of each of these.

Slide 8

What decides the properties of a polymer?

Stronger attractive forces between chains = stronger, less flexible polymer.

Chains able to slide past each other = flexible polymer .

In poly(ethene) attractive forces are weak instantaneous dipole - induced dipole, will it be flexible or not?

Nylon has strong hydrogen bonds, why does this make it a strong fibre?

Slide 9

Getting ideas straight

Look at page 110 -111 of Chemical Ideas.

Take turns in explaining to a partner how the following molecular structures affect the overall properties of polymers :-

chain length, different side groups, chain branching, stereoregularity, chain flexibility, cross linking.

Slide 10

Thermoplastics (80%)

No cross links between chains.

Weak attractive forces between chains broken by warming.

Change shape - can be remoulded.

Weak forces reform in new shape when cold.