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Materials Revolution
Explain and predict the effect of temperature, crystallinity and chain length on the properties of polymers

Temperature
Polymers are a mixture of amorphous (random) and crystalline (ordered) regions
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Consequently, movement between polymer chains before Tg is impossible, and if pressure is
applied the polymer simply breaks
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A this temperature the polymer is flexible
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Crystallinity
The greater the proportion of crystalline regions within a polymer, the more regular
packing of the chains
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Chain length
There are two ways in which increasing chain length increases tensile strength:
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The longer the chain length the greater the tangling of chains, meaning they are less
able to move past one another
The longer the chain length the greater the number of points of contact between
chains, meaning more intermolecular bonds are formed between them

It is important to note that increasing chain length does increase tensile strength; however a
certain length must be reached before strength increases
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A primary amine has one alkyl group and 2
hydrogen atoms
A secondary amine has two alkyl groups and 1
hydrogen atom
A tertiary amine has 3 alkyl groups and no
hydrogen atom

To name simple primary and tertiary amines with methyl and ethyl groups, we use the alkyl
as the prefix and amine as the suffix e
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the primary amine above is methylamine
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g
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g
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An amide is formed in the reaction between a carboxylic acid and amine – this is key in the
development of nylon
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These
usually contain a double bond which is broken
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Each molecule must have two appropriate functional groups to
form a bond on either side
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If only one monomer is used, it gives the chain A-A-A-A
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This reaction occurs very slowly naturally, and therefore an acid catalyst (dilute sulphuric
acid) is used
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Alternatively, adding an alkali (typically NaOH) rather than an acid produces a carboxylate
salt in place of the carboxylic acid
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Describe the reactions of amines

The amino group has basic properties, as the lone pair on the nitrogen is able to donate a
pair of electrons to form a dative covalent bond with a hydrogen atom – forming a cation
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Dissolve the substance in a minimal quantity of hot solvent – the smaller the
quantity of solvent used to greater the yield
o The solvent must one where the substance is soluble at high temperatures
and insoluble at low temperatures to ensure the maximum pure solid is
obtained
Filter insoluble impurities in a warm filter funnel and conical flask (to prevent
recrystallisation)
Allow to filtrate to cool and recrystallise
Vacuum filter and collect the pure crystals of organic solid left over
Leave to dry

Understand how the principles of green chemistry are important in the manufacture, use, recycling and
disposal of polymers

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Minimise the production of hazardous waste in use of raw materials in polymer
production
Reduce carbon emissions by recycling polymers to minimise the making of new
polymers/extending the useful life
Recycling can also occur by reacting polymers to reform their monomers and
cracking to form smaller useful molecules



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