Polymers
Learning Objectives
the formation of polymers from monomers including addition polymerisation of alkenes
the distinction between linear (thermoplastic) and cross-linked (thermosetting) polymers with reference to structure, bonding and properties including capacity to be recycled
Summary Notes
What is a polymer?
Polymers are large molecules that are made up of smaller building blocks (monomers) which are chemically bonded together.
Polymers are known as plastics and can have a range of uses from milk bottles, to money to combs!
How are polymers made?
The process of 'addition polymerisation' is used to create polymers. These are about multiple alkenes (see organic chemistry functional group if you are unsure of this) which is the monomer bonding together through the breaking of the double bond.
We can either draw the whole chain out or like the picture shows, use an 'n' to symbolise how many monomers are the in the chain. We can get up to 20000 carbon atoms in a chain!
LDPE vs HDPE
Chains of polymers can bunch together to form materials and there are two main types - High Density Polyethene (HDPE) and Low Density Polyethene (LDPE).
HDPE is when the different chains of polymers compact together. This means that together they are very rigid and are often not so transparent as many layers of polymers are layered on top of each other.
LDPE is when the different chains of polymers can't fit nicely on top of each other. This might be due to big side chains and branching. This means they are more flexible and are more transparent as there are often gaps between the polymer chains.
You can see the videos for more information on these and thermosetting vs thermoplastic polymers.