Predicting & Deducing the Type of Polymerisation (Cambridge (CIE) A Level Chemistry): Revision Note
Predicting Type of Polymerisation
When a set of monomers is given in an exam question, the type of polymerisation can be determined
Firstly, it’s important to identify the key functional groups in the monomers
Addition polymerisation
If the monomer/s contain a C=C double bond, they will polymerise through addition polymerisation
The double bond can open up in order to add more monomers on either side of the starting monomer
This type of polymerisation makes (poly)alkenes
Addition polymerisation using one monomer
During addition polymerisation of one alkene monomer, a (poly)alkene is formed
(Poly)alkenes can be produced if there are 2 or more alkene monomers as well
When more than one monomer is used for addition polymerisation, the resulting product is known as a copolymer
Addition polymerisation using more than one monomer
Addition polymerization can also use two or more different alkene monomers forming a co-polymer
Condensation polymerisation
Condensation polymerisation makes polyamides and polyesters
When looking to identify this type of polymerisation, there are some key functional groups to be aware of
Monomers for condensation polymers table
Polyamide monomers | Polyester monomers | Molecule expelled as a result of condensation polymerisation |
|---|---|---|
Acyl chlorides (–COCl) Amines (–NH2) | Acyl chlorides (–COCl) Alcohols (–OH) | Hydrochloric acid (HCl) |
Carboxylic acids (–COOH) Amines (–NH2) | Carboxylic acids (–COOH) Alcohols (–OH) | Water (H2O) |
Aminocarboxylic acids (H2N–CHR–COOH) | Hydroxycarboxylic acids (HO–R–COOH) | Water (H2O) |
Examiner Tips and Tricks
As well as the functional groups to be aware of, know that a small molecule is expelled when the polymer is formed
Identify 2 functional groups that can react together to produce either a polyamide or a polyester
There are instances where both of the functional groups are on the same monomer molecule
For example, amino acid molecules contain an amine group (-NH2) and a carboxylic acid group (-COOH) which means that they can polymerise to produce a polyamide
Deducing Type of Polymerisation
The type of polymerisation can be determined by considering the structure of the polymer backbone
Identifying addition polymerisation
The polymer backbone of an addition polymer does not contain functional groups
The backbone of the polymer is generally a chain of carbon atoms
There may be sidechains branching off from the backbone
Some examples of side chains include:
Benzene rings
Nitrile groups (-CN)
Halogen atoms (-F / -Cl / -Br / -I)
Identifying addition polymers
Addition polymers are identified using the plain carbon chain as the polymer backbone
Identifying condensation polymerisation
A condensation polymer can be identified by functional groups on the polymer backbone
The backbone of polyesters contains ester links (-COO-)
The backbone of polyamides contains amide / peptide links (-CONH-)
Identifying condensation polymers
Condensation polymers are identified using functional groups that form part of the polymer backbone, e.g. ester links in polyesters and amide / peptide links in polyamides
Examiner Tips and Tricks
Different sections of polymer chains may be formed using various types of polymerisation
In an exam, you may be given a section of a polymer and asked to determine the type of polymerisation used to form that section
Firstly, look at the polymer backbone
If there are functional groups along the backbone, that section was made using condensation polymerisation
If there are no functional groups along the backbone, addition polymerisation was used
You've read 0 of your 5 free revision notes this week
Sign up now. It’s free!
Did this page help you?