Polymers (A Level only) (AQA A Level Chemistry)

Poly(phenylethene) is widely used as a polymer for many purposes such as packaging.
The structure of poly(phenylethene) is shown in Figure 1 below. 

Figure 1

Terylene was one of the first man made polymers produced to be used as fibres for Clothing. The structures of the two monomers used to make Terylene are shown in Figure 2.

Figure 2

Explain why poly(phenylethene) drawn in Figure 1 of part (a) is far less reactive than Terylene described in part (b).

Identify a solution that would break down Terylene but not break down poly(phenylethene).

The structure of Kevlar is shown in Figure 1. State the type of polymerisation and draw the two monomers used to make Kevlar. 

Figure 1

Draw a second strand of Kevlar underneath Figure 2 to show how the strands are attached to one another.

Use your diagram to explain why Kevlar can be used for making items that require high strength.

Figure 2

High density poly(ethene), HDPE, is an example of a polyalkene and is used to make items such as plastic pipes and washing up bowls.

State the difference in biodegradability between Kevlar and high density poly(ethene), HDPE. Use your knowledge of structure and bonding to explain this difference.

Draw the salt formed when Kevlar reacts with hot, concentrated sodium hydroxide and give the name of this type of reaction.

One of the following molecules in Figure 1 below can polymerise by reaction with itself.
Identify the molecule and justify your answer.

Figure 1 

                                                A         HOOCCH₂CH₂COOH 

                                                B         CH₃CH₂CONH₂                                   

                                                C         NH₂CH₂CH₂COCl 

                                                D         NH₂CH₂CH₂CH₂NH₂

Valylalanine in Figure 2 below, is an example of a dipeptide composed of two amino acids, valine and alanine.

When this compound is placed in acidic conditions, two species are formed.

Draw one of these two species. 

Figure 2

The structure of glycine, an amino acid, is shown below in Figure 3. 

Figure 3         

Unlike the polymers formed by condensation reactions, polyalkenes which are formed by addition polymerisation are not biodegradable. If not disposed of correctly, polyalkenes can end up in a landfill, or as pollution in rivers and oceans.

Discuss the advantages and disadvantages of the incineration and the recycling of polyalkenes.

Compound A, (CH₃)₂C=C(CH₃)₂, is a hydrocarbon that can undergo polymerisation and can also react with bromine water, decolourising it.

A dipeptide made from the amino acids cysteine and tryptophan is shown in Figure 1.

Cysteine contains a sulphur molecule. 

Figure 1 

Amino acids such as serine in Figure 2 will form polyamide links. Polyamides will contain the same type of links and these polymers can be used to form fibres suitable for weaving. Polymers formed from alkenes by additional polymerisation are usually took weak for this purpose.

 Figure 2

In terms of intermolecular forces between the polymer chains, explain why polyalkenes are not suitable to be used as fibres for weaving.

Serine is an example of an amino acid. Amino acids contain a chiral carbon and exhibit optical isomerism.

Nylon is an example of a synthetic polyamide and contains the same links as polypeptides. Nylon is the general name for a family of polyamides. A section of a nylon polymer is shown in Figure 1.

Figure 1
 

Nylon can be used to make clothing. Suggest why nylon should be protected from spillages of strong acids and alkalis.

Nomex, drawn in Figure 2, has a higher melting point than nylon and is used to make the flame resistant body suits worn by racing drivers.

Suggest a reason why the melting point of Nomex is higher than that of nylon.

Figure 2 

Draw the two monomers that are used to manufacture Nomex drawn in Figure 2 and give the formula of any by-products produced

A section of polymer is shown in Figure 1. 

Figure 1

Bis(2-ethylhexyl) adipate, shown in Figure 2, was one of the first plasticisers used to soften polychloroethene from the rigid plastic used for drain pipes and guttering to its more flexible version used in clingfilm.

Figure 2

Explain how this plasticiser softens polychloroethene.

Name the chemicals used to make bis(2-ethylhexyl) adipate, shown in Figure 2.

Figure 2

Explain why the chemicals, identified in part (c), that are used to make bis(2-ethylhexyl) adipate cannot form a condensation polymer.

Draw the repeat unit for the general condensation polymerisation of a dicarboxylic acid and a diol as shown in Figure 1.

 Figure 1

In terms of n, state the number of molecules of water formed in the condensation polymerisation reaction of a general dicarboxylic acid and a general diol as shown in Figure 1.

Figure 1

Using displayed formulae, write the balanced equation for the condensation polymerisation of the two monomers, propanedioyl dichloride and butane-1,4-diol.

Suggest an alternative pair of monomers that will produce the polymer from part (c).

One family of condensation polymers are the aramids, so called because of the arene rings that are linked together with amide bonds. Kevlar ® and Nomex ® are two common examples of aramids.

Kevlar ® has a variety of uses, including bulletproof vests and puncture resistant tyres, due to its strength and being lightweight. Nomex ® is most commonly used as a lining of the overalls worn by racing drivers and their pit crews as well as in the personal
protective equipment of firefighters due to its flame resistant properties.

Nomex ® is made from 1,3-diaminobenzene and 1,3-benzenedicarboxylic acid.

Draw the skeletal structures of these monomers.

Draw the structure of the Nomex ® polymer.

Kevlar ® is made from 1,4-diaminobenzene and 1,4-benzenedicarboxylic acid.

Draw two repeat units of the polymer to show the strongest intermolecular force in Kevlar ®. 

State whether Kevlar ® or Nomex ® will have the higher melting point.

Justify your answer.

Polyethylene terephthalate, PET, is an increasingly common polymer as it is lightweight and strong. The repeat unit of PET is shown in Figure 1.

Figure 1

PET is made from the two monomers terephthalic acid and ethylene glycol.

Give the systematic IUPAC names of these two monomers.

According to the Department for Environment, Food & Rural Affairs, 43.8% of the 2.361 megatonnes of the UK’s plastic waste was recycled in 2018.

Explain how the use of polyester based plastics such as PET can help with the UK waste plastic problem, even if it is not recycled.

Condensation polymers biodegrade more quickly on compost heaps than in landfill sites.

Suggest three reasons for this.

The main methods of polymer disposal are landfill, incineration and recycling.

Give three reasons why, despite its disadvantages, landfill is still the most effective method of waste disposal.

Lactic acid, C₃H₆O₃, is a carboxylic acid with a secondary alcohol functional group.

Draw the displayed formula of lactic acid.

Lactic acid can form the condensation polymer polylactic acid, PLA.

Draw a section of the PLA polymer showing two repeat units.

The structure in Figure 1 shows the repeat unit of a polymer.

 Figure 1

Give the IUPAC names of the monomers used to form this polymer.

The structures in Figure 2 are two possible repeat units of the condensation polymer formed by the reaction of 1,3-diaminopropane and butane-1,4-dioic acid.

Figure 2

Draw an alternative repeat unit for the same condensation polymerisation of 1,3-diaminopropane and butane-1,4-dioic acid.