B19MA1 and B19AB1

Practice Questions (from a previous Class Test)

1. Consider the reaction between the following monomers or pairs of monomers.

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a H2C CH b
COOC2H5
Ethyl acrylate
styrene and divinylbenzene
O O O
c d
HO C (CH2)4 C OH HO (CH 2)10 OH CH2OH
O HOH C C
Adipic acid and 1,10-decamethylene glycol 2 CH2OH
O CH2OH
Phthalic anhydride and pentaerythritol

Which of the monomers or monomer pairs give cross-linked networks when polymerised under
appropriate conditions?

… a … b … c … d

Which of the monomers give linear polymer chains?

… a … b … c … d

2. Consider the following monomers and state the monomer functionality in each case.

Monomer O
H2C CH C O CH2 CH CH2 CH2OH
CN HOH2C C CH2OH
CH2OH
C O CH2 CH CH2
O

Name Acrylonitrile Diallyl isophthalate Pentaerythritol

Functionality
3. What type of plastics does not melt when heated but will eventually burn at high temperatures?
… Thermoplastics
… Thermosets
… Thermoplastic elastomers

4. Which of the following monomers can conceivably form isotactic polymers?

Monomer Structure Yes No

A H H
H2C C C CH2
B CH3
CH3 C CH2
C H H
H3C C C CH2
CH3

5. Identify the following copolymers (A and B are chemically different repeat units):

b c

1. Structure a is a ……………………………….. copolymer

2. Structure b is a ……………………………….. copolymer
3. Structure c is a ……………………………….. copolymer

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6. (a) Write down the structure of a random copolymer of styrene and acrylonitrile, including at
least 6 repeat units.
H H
H 2C C H2C C Styrene
CN

Acrylonitrile

(b) Which polymerisation method would you choose to prepare this copolymer?

7. High-density polyethylene cooled slowly from 160 °C to room temperature

… is still amorphous
… crystallises
… is a glass
… is a mixture where some regions are rubbery and some regions are glassy

8. Which of the following polymers has the highest and which the lowest Tg ?
Highest Tg Lowest Tg
(a) −CH2CH2− … …
(b) −CH2CH(CH3)− … …
(c) −CH2CH(Cl)− … …
(d) −CH2CH2−O− … …

9. Linear chains of a nylon-6,6 sample will:

… interact strongly due to polar forces
… only interact weakly through dispersion forces
… form hydrogen bonds with one another

10. Sketch the copolymer composition diagram expected for the styrene (S) / butadiene (B)
copolymer system, given that the reactivity ratios are rS = 0.58 and rB = 1.4.

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11. The specific volume versus temperature curve
for unstretched (A) and stretched (B) rubber
samples is shown below.
Identify all transition temperatures
.

12. Consider the stress–strain diagram shown below. Clearly mark in the diagram: (a) the break
point, (b) the elastic modulus and (c) the tensile strength.

Which type of material will show this behaviour:

… natural rubber
… High-density polyetheylene
… atactic polystyrene

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Selected Exam questions

1. Styrene is a unique monomer, in that it can be polymerized by practically all methods of chain
polymerization : (a) free radical, (b) ionic (e.g. anionic) and (c) co-ordination (i.e. using a
catalyst).
(i) Which of the three polymerization methods listed above is used commercially to synthesize
atactic PS? Briefly explain.
(ii) Explain why polystyrene is capable of forming stereoisomers and draw the structure of three
different tactic forms (atactic, syndiotactic and isotactic)
(iii) Which of the three polymerization methods listed above would you choose to make isotactic
PS? Briefly explain.
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2. A sample of atactic polystyrene is separated into three monodisperse fractions containing ni

moles of molecules with molar mass Mi :

Fraction 1 Fraction 2 Fraction 3

ni 0.01 0.01 0.01
Mi 50,000 300,000 1,000,000

On the basis of the values reported above, calculate the number average molecular weight Mn,
the weight average Mw and the polydispersity.
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3. How would you prepare random copolymers of styrene and p-methyl styrene ?
The reactivity ratios for styrene (monomer 1) and p-methylstyrene (monomer 2) are r1 = 0.98
and r2 = 0.95. Sketch the copolymer composition diagram expected for this system.
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4. Explain briefly what is meant by the glass transition temperature of a polymer.

(i) Sketch the temperature dependence of specific volume across the polymer glass transition and
describe, in molecular terms, the observed changes.
(ii) Briefly outline the effects on the glass transition temperature of introducing bulky side groups
onto the polymer chain.
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5. Atactic poly(p-methyl styrene) has a glass transition at 97 oC. Is this a rigid or flexible plastic?
Sketch the expected stress-strain curve.
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