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PRACTICE PROBLEMS FOR
STUDENT USE
CHAPTER 20: PHARMACEUTICAL POLYMERS
20–1
20–2
20–3
20–4
There are three monomers: M1, M2, and M3; M1
contains one double bond and no functional group,
M2 contains one reactive functional group and no
double bond, and M3 contains two reactive functional groups and no double bond. Which statement is
true?
(a) All three monomers can be polymerized via addition and condensation polymerization.
(b) M1 can be polymerized via addition, M2 cannot
be polymerized, and M3 can be polymerized via
condensation.
(c) M1 can be polymerized via addition, and both M2
and M3 can be polymerized via condensation.
(d) None of the monomers are polymerizable.
Which statement is true regarding polymer molecular
weight?
(a) Number average molecular weight is related to
the size of the polymer chains.
(b) Weight average molecular weight is related to the
number of polymer chains.
(c) Polydispersity is related to the number and the
size of the polymer chains.
(d) Number average molecular weight is always bigger than the weight average molecular weight.
The Tg values of the two polymers P1 and P2 are
−20◦ C and 100◦ C, respectively. Which statement is
true?
(a) At room temperature of 25◦ C, both P1 and P2 are
rubber.
(b) At room temperature of 25◦ C, P1 is rubber but P2
is glass.
(c) At room temperature of 25◦ C, both P1 and P2 are
glass.
(d) At room temperature of 25◦ C, P1 is glass but P2
is rubber.
Which statement is false regarding the Tg and Tm of a
given polymer?
(a) Tm is a first-order thermal transition but Tg is a
second-order one.
(b) Tg and Tm are related to the amorphous and crystalline parts of the polymer chain, respectively.
(c) Tg has a broader temperature range than does Tm .
(d) For a given polymer, Tg is always higher than Tm .
20–5
Which statement is true for the elastic properties of
polymers?
(a) A low modulus polymer is stiffer than a high modulus polymer.
(b) A high modulus polymer is tougher than a low
modulus polymer.
(c) Stiffness is the ratio of strain to stress.
(d) Toughness is the area under stress and strain
curve; energy to break.
20–6
If you are asked to increase the viscosity of water with
a minimum amount of the following polymers, which
polymer would be your choice?
(a) A very hydrophilic and low-molecular-weight
polymer.
(b) A very hydrophilic and high-molecular-weight
polymer.
(c) A very hydrophobic and low-molecular-weight
polymer.
(d) A very hydrophobic and high-molecular-weight
polymer.
20–7
In preparing a water-soluble polymer, which action
would be wrong?
(a) Using a water-soluble monomer
(b) Utilizing emulsion technique
(c) Utilizing inverse-emulsion technique
(d) Utilizing inverse-suspension technique
20–8
Pseudo latex is a
(a) Dispersion of a monomer in water.
(b) Dispersion of a water-soluble polymer in water.
(c) Dispersion of a water-insoluble polymer in water
using high HLB surfactant(s).
(d) Dispersion of a water-insoluble polymer in water
using low HLB surfactant(s).
20–9
Which of the following statements is true for a dispersion system?
(a) In a W/O system, the dispersed phase is water,
and the continuous phase is oil.
(b) In an O/W system, the dispersed phase is oil, and
the continuous phase is water.
(c) Surfactant should be more soluble in the continuous phase.
(d) Surfactant concentration determines the size of
the dispersed phase.
(e) All of the above are true.
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STUDENT PRACTICE PROBLEMS: CH. 20
20–10 Which of the following polymers can be used as an
enteric coating material?
(a) An anionic polymer.
(b) A cationic polymer.
(c) An amphoteric polymer.
(d) Both anionic and cationic polymers.
20–16 A polymer sample was fractionated into three homo-
geneous or monodisperse fractions as follows:
Data for Problem 20–16
Fraction
20–11 For taste-masking application, what polymer would
you not recommend to use?
(a) A polymer which is soluble in water at neutral
pH.
(b) A polymer which is soluble in water at low pH.
(c) A polymer which is insoluble in water at all pHs.
(d) An oil-soluble polymer.
20–12 Which statement is false about polydispersity and
chain length?
(a) A monodispersed polymer contains similar
chains.
(b) A polydispersed polymer contains different
chains.
(c) Polydispersity 1 means polymer chains are very
different in size.
(d) Polydispersity is always lower than 1.
20–15 A pharmaceutical packaging material requires being
a tough polymer, the tougher the better. After testing different polymers using a mechanical tester, you
select
(a) A polymer which shows high modulus.
(b) A polymer which deforms less at its failure or
breaking point.
(c) A polymer which shows high stiffness.
(d) A polymer whose force-deformation curve has the
largest area.
10
B
20
C
100
100,000
10,000
20–17 A sample of polyvinyl chloride was fractionated from
its solution in tetrahydrofuran. The weight percent
(based on the weight of the entire sample) and the
molecular weight (g/mole) of successive fractions
were as follows:
Data for Problem 20–17
Fraction
Number
mer 1 (−90◦ C) and polymer 2 (90◦ C). If you are asked
to coat your tablet with these polymers, which one
would you select?
(a) Polymer 1.
(b) Polymer 2.
(a) Polymers do not exist as gas.
(b) Monomers containing double bond may be polymerized via free radicals.
(c) Polymers containing high concentrations of residual monomers may not be suitable for pharmaceutical use.
(d) Different isomers of a polymer have same physicochemical and mechanical properties.
A
Molecular Weight
Given that the weight-average molecular weight of
the entire sample is 23,000, calculate the molecular
weight of fraction B.
20–13 You have two polymers with different Tg values: poly-
20–14 Which statement is false?
Weight, Grams
Weight (%)
Molecular Weight
1
6
7 × 103
2
9
1.7 × 104
3
15
3.8 × 104
4
20
7.5 × 104
5
23
1.4 × 105
6
16
2.5 × 105
7
8
4.5 × 105
8
3
1.05 × 106
Assuming that the fractions are essentially
monodisperse, calculate M z , M w , M n , and M w /M n
of the polyvinyl chloride sample.
20–18 Will the intrinsic viscosity of polyethylene oxide
increase, decrease, or remain unaffected as the temperature of its aqueous solution is increased?
Hint: Express your answer in terms of hydration.
20–19 The melting points of some isotactic polyolefins
[ CH2 CH ] are as follows:
R
R
Melting Point, ◦ C
E
CH3
165
F
C2 H5
125
G
CH2 CH2 CH3
75
Explain the trend in melting point when going from
E to F to G.
STUDENT PRACTICE PROBLEMS: CH. 20
20–20 Drugs targeted for colon diseases may be formulated
into a material (a polymer) which can protect them
from the harsh low pH environment of the gastric
medium. The material selected for such application
should have
(a) High solubility or complete solubility at low
pH.
(b) No solubility or low solubility at low pH.
20–21 Coacervation is a process by which a drug is encap-
sulated inside a polymeric matrix by precipitating
the polymer in solution. If the drug is sensitive to
heat and acid, which option would be least attractive for precipitating the polymer from its aqueous
solution?
(a) Increasing the temperature of the polymer solution.
(b) Adding an effective but permitted amount of alcohol to the polymer solution.
(c) Increasing the pH of the polymer solution.
(d) Increasing the ionic strength of the polymer solution by adding reasonable amounts of salts.
20–22 Which of the following materials displays thermo-
gelling at a higher temperature?
(a) Cellulose (has no solubility in water).
(b) Cellulose with methyl substitution (it is soluble
in cold water).
(c) Thermogelling is not dependent on the number
and nature of substituents.
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(d) Cellulose with methyl and hydroxypropyl substitution (it is soluble in water over a wider temperature range).
20–23 If the solution property of a material is sensitive
to temperature, that material displays thermogelling
property. Which of the following materials less likely
displays a thermogelling property?
(a) A material containing both hydrophilic and hydrophobic groups.
(b) A material with ionizable hydrophilic groups.
(c) A material whose chains can aggregate if temperature changes.
(d) A material whose hydrophobic groups associate
if temperature rises.
20–24 Swelling concept has found applications in which of
the following areas?
(a) Superdisintegrants, which are used in tablets and
capsules to help the dosage form to disintegrate
properly.
(b) Osmotic tablets (Oros technology), which can
deliver the drug at a constant rate over a 24-hr
period.
(c) Implantable osmotic pumps (Duros technology),
which can deliver the drug over a few months to
a 1-year period.
(d) Superabsorbent polymers, which are used in ultrathin baby diapers to absorb baby’s urine.
(e) All of the above.