Material Revolution

A summary of the materials revolution topic

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  • Created by: R_Hall
  • Created on: 15-01-14 22:00

5.7 Polymer Properties by Design

  • In addition polymerisation, the monomers join together to give a polymer only. In condensation polymerisation, the monomers join together to give a polymer and another small molecule
  • When polymers are cooled, they become glassy. In the glassy state, the amorphous regions become frozen so chains cannot easily move. The only way the polymer can change shape is through breaking
  • If you heat up the glassy material, the polymer chains will reach a temperature where they can move relative to each other- the glass transition temperature (Tg). On further heating, the melting temperature (Tm) is reached- the crystalline areas break down and the polymer becomes a viscous fluid
  • Longer chains make stronger polymers- the chains get more tangled, reducing flexibility as the chains cannot slide. Longer chains have more points of contact with other chains, so more intermolecular bonds hold them together.
  • To increase flexibility, polymers can be copolymerised with another molecule, or a plasticisier can be added to allow chains to slide
  • Crystalline area- an area where the chains are closely packed in a regular way. The more crystalline a polymer, the stronger and less flexible it is
  • When a polymer is stretched (cold-drawn) a neck forms, in which the polymer chains are lined up to form crystalline regions -> increase in strength
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13.8 Amines and Amides

  • Amines are relatives of ammonia. Amines with one alkyl group are primary amines (eg. methylamine), 2= secondary (eg. dimethylamine), 3= tertiary (eg. trimethylamine)
  • Amines with two amino groups attached are diamines (eg. 1,3-diaminopropane)
  • Amines have a lone pair of electrons on the nitrogen atom, so are very soluble in water (form H bonds with H2O), bases, ligands and nucleophiles.
  • The lone pair can form dative covalent bonds- when e- donated to an H+, amine acts as a base to form an ammonium + ion. Amines react with acids also
  • Ammonia is an effective ligand as the lone pair on the N can bond to metal ions. The lone pair also attack electrophiles to act as a nucleophile
  • Acylation is when an acyl group is added to the amine to form an amide- this reaction is very vigorous
  • The C-N bond in amides can be broken by hydrolysis if catalysed by heating under reflux with -acid or alkali (moderately concentrated). If an acid catalyst -> ammonium ion + carboxylic acid, if alkali catalyst -> carboxylate ion + ammonia
  • When an -NH2 group reacts with a -COOH group, a secondary amide group is formed. This is a condensation reaction
  • If diamine and dicarboxylic acids (acyl chlorides) are used, a chain is formed, through condensation polymerisation. The polymers are called polyamides or nylons
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15.10 Green Chemistry and Recycling

  • In addition to reducing the amount of plastic waste requiring disposal, recycling of plastics serves to
  • Conserve fossil fuel feedstocks
  • Reduce consumption of energy
  • Reduce the amount of solid waste going to landfill
  • Reduce CO2, NO and SO2 emissions
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