Chemistry A2 Salters mindmap on polymer properties.

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  • Polymer properties by design.
    • How do temperature changes affect polymers?
      • At room temp, most polymers have some crystalline regions (highly ordered chains) and some amorphous regions (randomly arranged chains).
      • Cooling the polymer gives a higher % of crystalline regions. Eventually, glass transition temperature (Tg) is reached and polymer becomes brittle or glass like.
      • As a polymer warms up, polymer chains slide over each other more easily, making it increasingly flexible. After continued heating, the melting temperature (Tm) is reached and polymer becomes liquid.
    • Bonds between polymer chains
      • Individual polymer chains are held together by intermolecular bonds. The longer the polymer chains, the stronger the polymer = more intermolecular bonds.
      • Both nylons and polyesters form linear polymer chains, making them ideal for use as fibres.
      • Hydrogen bonding holds nylon chains together.
      • Permanent dipole - permanent dipole bonds hold polyester chains together.
    • Two different monomers join together forming a condensation polymer. At the same time, a small molecule, often water or hydrogen chloride, is eliminated.
    • 2 common groups of condensation polymers = polyamides (nylons) & polyesters. Polyamides = condensing diamines and dicarboxylic acids. Polyesters = condensing diols & dicarboxylic acids.
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      • Adding plasticisers also lowers Tg. (Molecules that sit between polymer chains, allowing them to slide more freely.


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