A-Level Chemistry OCR Notes

6.2.3 Polyesters and polyamides

Polyesters and polyamides
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Condensation Polymers
  • Condensation polymerisation involves the reaction of two different types of monomers, with different functional groups.
  • Reacting dicarboxylic acids with diols forms polyesters
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  • Square brackets with bonds through them are used to represent a repeat unit of a polymer
  • Adjacent polyester chains are held together by permanent dipole-dipole attractions due to the presence of the polar carbonyl group
  • The polyester terylene (PET) is formed from the monomers terephthalic acid and ethylene glycol. Typically used in plastic bottles, sails, sheets and clothing
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  • Reacting dicarboxylic acids and diamines forms polyamides
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  • Adjacent polyamide strands are held together by hydrogen bonds
  • Nylon is a polyamide used in textiles
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  • ​Kevlar is a polyamide used in bullet and stab-proof vests
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  • Polypeptides are also condensation polymers made up of amino acids
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​Hydrolysis of Polymers
  • Polyesters and polyamides undergo acid hydrolysis with a strong aqueous acid, or base hydrolysis with hot aqueous sodium hydroxide
  • Acid hydrolysis of a polyester produces a diol and a dicarboxylic acid
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  • Alkali hydrolysis of a polyester produces a diol and the salt of a dicarboxylic acid
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  • Acid hydrolysis of a polyamide produces a diammonium salt and a dicarboxylic acid
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  • Alkali hydrolysis of a polyamide produces a diamine and the salt of a dicarboxylic acid
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