BIRLA INSTITUTE OF TECHNOLOGY AND SCIENCE-PILANI,
Hyderabad CAMPUS
Comprehensive Exam (Regular) Closed Book FIRST SEMESTER 2018-2019 Time: 3hrs
Part B (2hrs, 60 Marks) Max. Marks – 90M Date: 04/12/2018
COURSE NO: CHEM F325 Weightage: 45%
COURSE TITLE: POLYMER CHEMISTRY
Instruction: This paper consists of two pages, ensure both sides of the paper are printed.
There are overall FIVE questions. Answer all questions. All parts of the question should be
answered together. Start a new question from a fresh page.
1. (a) Which one will have higher Tg in between cis- and trans-polybutadiene and why?
Why polydimethylsiloxane has very low Tg?
[1+1+1=3M]
(b) Determine the density of totally crystalline PTFE polymer while the densities of the
same polymer samples with 51.3 and 74.2 % crystallinity are 2.144 and 2.215 g/cm3
respectively. [1+1+1=3M]
(c) What is the significance of rubber plateau of a polymer reading thermal transition?
Explain by proper plotting how the rubber plateau and relaxation modulus will differ will
differ in amorphous, largely crystalline and highly cross-linked polystyrene polymers?
[2+1+1+1 = 5M]
2. (a) What are the major and minor groove in a DNA double helix structure?
[1+1=2M]
(b) Why does incineration of PVC require higher temperature? Why is starch used as an
additive with polyethylene polymers? [2+2=4M]
(c) Why does the polyvinylchloride (PVC) pipe change it color from white to yellow to
brown in prolong use? Name two additives which can stabilize the PVC and explain
briefly there mechanism.
[2+3=5M]
3. (a) Expand the trade names for the polymers given below and write the molecular
structures of the compounds along with their preparative reaction and one application.
(i) PEEK (ii) PBT (iii) PPO [33=9M]
(b) Poly(methylmethacrylate) (PMMA) polymer is called acrylic glass as it is transparent
like glass. However, when it is stretched adiabatically, it becomes opaque with elevated
temperature. Why? [2M]
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4. (a) Acid doped polyaniline polymers usually exhibit a broad absorption band around 600-
900 nm. What is the origin of the band? What would be the effect of pH on the color of
polyaniline polymer solution?[1+2=3M]
(b) What is the difference between ionomer and polyelectrolyte? Why alumino silicate
polyacrylic acid based glass ionomer is used as dental cement?
[2+2=4M]
(c) Answer in one word or in one sentence [80.5= 4M]
(i) Name a proton conducting polymer used in fuel cell technology.
(ii) What kind of functional group containing additive will be suitable for the curing of
epoxy resin?
(iii) Name a metathesis elastomer.
(iv) What is ‘gutta percha’?
(v) What is the advantage of vulcanization of rubber?
(vi) What is the Zeigler-Natta catalyst?
(vii) What is LCST?
(viii) Name a liquid crystalline polymer.
5. (a) Draw a sketch of the Zimm plot for a solution of a polymer with the same M W and s2
but with A2 just the opposite in sign. [5M]
(b) What is Mark-Howink Sakurada Equation? How can the constant K and exponent
be obtained by simple experiments and used for the determination of molecular weight of
polymer? [4M]
(c) What are the upper and lower limits of molecular weights between which the light
scattering method can be used? What determines these values? [4M]
(d) In the dissymmetry method of molecular weight determination, the scattered
intensities at three angles 45, 90 and 135 for a dilute polymer solution was noted to be
1.8106, 1.6106 and 1.4106 respectively. Calculate the dissymmetry ratio. [3M]
END
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