CIE A Level Chemistry复习笔记7.7.3 Repeat Units & Monomers

Deducing the Repeat Unit of a Condensation Polymer

  • In condensation polymerisation the monomers either contain 2 of the same functional group or one single monomer has both functional groups needed for polymerisation
    • For example Diamine and dicarboxylic acid
    • Or an aminocarboxylic acid
  • When presented with 2 monomers there are steps to take in order to deduce the repeat unit of a condensation polymer

Exam Tip

  • Remember: in condensation polymerisation, a small molecule is expelled as a result of the 2 monomers joining together.
  • When a dioic acid and diamine polymerise, a water molecule is expelled
    • OH from acid and H from the amine
  • When a dioyl acid and diamine are polymerised, a hydrochloric acid molecule is expelled
    • Cl from the dioyl acid and H from the amine

Identifying Monomers in Condensation Polymers

  • When a section of polymer is presented, the monomers can be identified by considering the small molecules expelled from the monomers
  • If a water molecule is expelled, the -OH must have been from an acid group
  • The hydrogen atom may be from an amine group of a monomer.
  • If the molecule was hydrochloric acid (HCl), a dioyl chloride monomer may have been used