Polymers

• Addition polymers are produced from alkenes where the double bond is broken to form a repeating unit.
• For addition polymers, high temperatures and pressures produce branched chain polymers with weak intermolecular forces, whereas lower temperatures and pressures produce straight chain polymers with strong intermolecular forces.
• Addition polymers are unreactive hydrocarbon chains with multiple strong, non- polar covalent bonds making them unreactive. This makes them useful for plastic products but means they are not biodegradable.
• PVC is an addition polymer with waterproof properties due to the addition of plasticisers during the polymerisation reaction.
• Condensation polymers form when a water molecule is removed from the species of a reaction. There are three main types: polyamides, polyesters, and polypeptides.
• Polyamides are formed in a reaction between dicarboxylic acid and a diamine, leaving an amide linkage: - CONH -.
• Nylon-6,6 is a polyamide made from 1, 6 - diaminohexane and hexanedioic acid, and is used for man made clothing fibre.
• Kevlar is a polyamide made from benzene - 1, 4 - dicarboxylic acid and 1, 4 -diaminobenzene, and is used for bulletproof vests.
• Polyesters are formed in a reaction between dicarboxylic acids and a diol, producing an ester linkage: - COO -.
• Terylene (PET) is a polyester made from ethanediol and 1, 4 - benzenedicarboxylic acid, and is used for fire resistant clothing.
• Polypeptides are formed from multiple amino acids, and have a peptide linkage: - CONH -.
• A single amino acid monomer can produce a polymer due to the presence of both a NH and OH group.
• Condensation polymers can be broken down into their constituent molecules in hydrolysis by the addition of water as water is attracted to the polar regions of the polymer.
• Condensation polymers contain polar bonds, and hydrogen bonds and dipoles can form between separate polymer chains, causing them to have a very strong structure.
• Polyesters and polyamides are biodegradable as they can be broken down by hydrolysis.