The Structure and Properties of Polymers
Also known as
A long molecule made up from lots of small molecules called
Monomers all same type (A)
A + A + A + A
eg poly(ethene) polychloroethene PVC
Monomers of two different types A + B
A + B + A + B
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’
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!
Find a definition and suggest your own example of each of these.
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?
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.
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.