EDEXCEL IGCSE CHEMISTRY: DOUBLE SCIENCE 复习笔记:4.5.1 Addition Polymers

EDEXCEL IGCSE CHEMISTRY: DOUBLE SCIENCE 复习笔记:4.5.1 Addition Polymers

Monomers

 

  • Polymers are large molecules of high relative molecular mass and are made by linking together large numbers of smaller molecules called monomers
  • Each monomer is a repeat unit and is connected to the adjacent units via covalent bonds
  • Polymerisation reactions usually require high pressures and the use of a catalyst
  • Many everyday materials such as resins, plastics, polystyrene cups, nylon etc. are polymers
  • These are manufactured and are called synthetic polymers
  • Nature also produces polymers which are called natural or biological polymers

 

 

Diagram showing how lots of monomers bond together to form a polymer

 

 

Drawing Polymers

 

  • Addition polymers are formed by the joining up of many monomers and only occurs in monomers that contain C=C bonds
  • One of the bonds in each C=C bond breaks and forms a bond with the adjacent monomer with the polymer being formed containing single bonds only
  • Many polymers can be made by the addition of alkene monomers
  • Others are made from alkene monomers with different atoms attached to the monomer such as chlorine or a hydroxyl group
  • The name of the polymer is deduced by putting the name of the monomer in brackets and adding poly- as the prefix
  • For example if propene is the alkene monomer used, then the name is polypropene
  • Polyethene is formed by the addition polymerisation of ethene monomers

 

Examples of addition polymerisation: polyethene and PVC

 

 

Deducing Monomers & Repeat Units

 

Deducing the monomer from the polymer

  • Polymer molecules are very large compared with most other molecule
  • Repeat units are used when displaying the formula
  • To draw a repeat unit, change the double bond in the monomer to a single bond in the repeat unit
  • Add a bond to each end of the repeat unit
  • The bonds on either side of the polymer must extend outside the brackets (these are called extension or continuation bonds)
  • A small subscript n is written on the bottom right hand side to indicate a large number of repeat units
  • Add on the rest of the groups in the same order that they surrounded the double bond in the monomer

 

 

Diagram showing the concept of drawing a repeat unit of a monomer

 

 

 

Deducing the polymer from the monomer

  • Identify the repeating unit in the polymer
  • Change the single bond in the repeat unit to a double bond in the monomer
  • Remove the bond from each end of the repeat unit and the subscript n (which can be placed in front of the monomer)

 

 

Diagram showing the monomer of the repeat unit of polymer

转载自savemyexams

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