Questions on Polymers

1. (a) Explain why the atom economy for most addition polymers is close to 100%.

(b) Nylon 6,6 can be made by reacting 1,6-diaminohexane, H₂N-(CH₂₎₆-NH₂, with hexanedioyl dichloride, ClCO-(CH₂)₄-COCl. The reaction is a condensation reaction in which peptide bonds, –CO-NH–, are formed with the loss of hydrogen chloride.
The equation for the reaction is:

nH₂N(CH₂)₆NH₂ + nClOC(CH₂)₄COCl → H−[HN(CH₂)₆NHCO(CH₂)₄CO]_n−Cl + (2n−1)HCl

If n = 1000 and the reaction gives a 90% yield of nylon 6,6 calculate the atom economy for this reaction.

2. Poly(chloroethene) also known as poly(vinylchloride) or PVC can be mIB Docs (2) Teamfactured so that the polymer can have very different properties. It can be made quite rigid to form plastic guttering or drain pipes or it can be made quite flexible for use as insulation around wire
cables.

(a) Draw a section of PVC that contains six carbon atoms.

(b) Describe how the flexibility of PVC can be increased during its mIB Docs (2) Teamfacture.

(c) Explain why PVC becomes more flexible during the process described in (b).

3. (a) Poly(2-methylpropene) is an elastomer.
Explain the meaning of the term elastomer and give one example for a use of poly(2-methylpropene).

(b) Poly(propene) can polymerise either to form a tough crystalline product known as isotactic poly(propene) or a more soft flexible form known as atactic poly(propene).
Show by means of clear diagrams the difference in the structures of isotactic poly(propene) and atactic poly(propene).

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