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Condensation Polymers
Organic
A2
Polymers
AQA Content
Draw the repeating unit from monomer structure(s)
Draw the repeating unit from a section of the polymer chain
Draw the structure(s) of the monomer(s) from a section of the polymer
Explain the nature of the intermolecular forces between molecules of condensation polymers.
Specification Notes
Condensation polymers are formed by reactions between:
dicarboxylic acids and diols
dicarboxylic acids and diamines
amino acids.
The repeating units in polyesters (eg Terylene) and polyamides (eg nylon 6,6 and Kevlar) and the linkages between these repeating units.
Typical uses of these polymers.
Notes
A polymer is produced by repeated condensation reactions between monomers
Condensation polymerisation involves the elimination of a small molecule - the monomers are linked by ester or amide bonds. Natural condensation polymers are all formed by elimination of water
Polyesters
Polyester involves diol and dicarboxylic monomers – allows monomers to join on either side of the molecules.
Links formed are ester bonds
A hydroxyl from the diol and hydrogen on the dicarboxylic acid are removed as water and the ester bond forms.
Hydroxycarboxylic acids can also be used to make a polyester
These monomers contain an alcohol group (-OH) and a carboxylic acid group at the ends of the molecule.
This monomer will join together through ester bonds and a water molecule will be eliminated.
Polyamides
Polyamides have repeating units joined by amide/peptide links (CONH):
A diamine and a dicarboxylic acid are required to form a polyamide
Dioyl dichlorides can also used with a diamine...
Even though they are more reactive than a dicarboxylic acid, the dioyl dichloride is a lot more expensive.
Proteins
Proteins are polymers consisting of amino acid monomers. These monomers have an amino-carboxylic acid structure joined through amide/peptide links. The properties depend on the nature of the R-group side chain.
Intermolecular Forces
Condensation polymers can be drawn out to form fibres - the linear molecules align and are linked by hydrogen bonds. The strength of the fibre increases as the fibre is drawn out. Straighter chains equate to more effective hydrogen bonding - the polymer will have a higher melting point.
Examples of Synthetic Polymers
Polyesters
Terylene (polyethylene terephthalate or PET) is a thermoplastic polyester polymer – therefore reusable. Extruded to form fibres or moulded into containers
Polyamides
Nylon is an artificial polyamide. Nylon-6,6 contains a diamine and dicarboxylic acid, each having six carbon atoms. Silk substitute = cheap. Also used to make ropes and Velcro®. The reaction between the monomers is slow, so the dicarboxylic acid is usually converted to a diacyl dichloride which is then used in the polymerisation.
The resulting repeating unit after water is condensed:
The polymer structure:
Aromatic polyamides (aramids)
Examples include Nomex® and Kevlar®
Tough and lightweight, they are used in bulletproof vests and fireproof suits.
Kevlar®
The chains of the polymer are neatly arranged - lots of hydrogen bonds so it is a very strong yet flexible polymer with fire resistance properties.
The polymer structure looks like this...
Hydrogen bonding can occur between the oxygens and nitrogens on different chains
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