Sample Questions for Polymer Chemistry PDF

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Sample questions for Polymer Chemistry 1) Outline the differences between suspension and emulsion polymerisation. Give 3 examples made by each method. (8 marks) 2) In the step-growth polymerization of this monomer:

CH2N

CH2 COOH

220 °C

NH

10

C

CH2 10

O

n

Molecular weight of repeating unit 183 g mol-1 How much monomer (in terms of weight fraction of the reaction mixture) is left when 90 % of the functional groups have reacted? (3 marks) """"" """" 𝑀! , $𝑀 Calculate """" " , $𝑀# $of the reaction mixture at this stage. (12 marks) 3) You have made a polystyrene with number molecular weight of 138,000 from 1.0 M styrene in benzene. This is too high. What concentration of t-butyl mercaptan should be used to lower the number molecular weight to 85,000? For this, the transfer agent C is 3.7 in the polymerization of styrene. (Mw of styrene = 104 g mol-1). (6 marks) 4) For acrylamide (Mw 71 g mol-1) , kp2/kt = 22 L m-1 sec-1 at 25 °C and termination is by coupling alone. At this temperature, the half-life of isobutyryl peroxide (initiator) is 9 h, and its efficiency in methanol is 0.3. A solution of 100 g/liter acrylamide in methanol is polymerized with 10-1 M isobutyryl peroxide. What is the initial steady-state rate of polymerization? (11 marks) How much polymer has been made in the first 10 min of reaction in 1 liter of solution? (9 marks) 5) The reactivity ratios of the following monomers are: M1 Ethylene Styrene Acrylonitrile

M2 Vinyl acetate Methyl methacrylate Styrene

r1 1 0.5 0

r2 1 0.5 0.8

(i) Which combination will produce a homopolymer, alternating polymer, and a random polymer? Briefly explain each case. (6 marks) (ii) In the copolymerisation of butadiene and styrene, what monomer feed composition is required to produce a copolymer containing 7 mol% of styrene? (10 marks)

6) The following data were calculated for a copolymer synthesised from A and B assuming the terminal model. Copolymer composition: A = 0.87, B = 0.13 Number Ave Length of Runs: ĪA = 10.6, ĪB = 1.5 Deviation from Randomness: χ = 0.76 Number Fraction of (A)n Sequences: (A)1 = 0.10 (A)2 =0.09 (A)3 = 0.08 Number Fraction of (B)n Sequences: (B)1 = 0.66 (B)2 =0.22 (B)3 = 0.08 What do these data tell you about the copolymer microstructure? (8 marks)

7) Consider the following distribution of polymer chains: 5 chains of degree of polymerisation 10 25 chains of degree of polymerisation 100 50 chains of degree of polymerisation 500 30 chains of degree of polymerisation 1000 10 chains of degree of polymerisation 5000 5 chains of degree of polymerisation 50000 (i) .Calculate the number and weight average degree of polymerisation and the polydispersity of this collection of polymer chains. (3 marks) (ii) Consider these chains are poly(methyl methacrylate)s. What would be the corresponding number, weight average molecular weights, and polydispersity (ignore end group effects)? (Methyl methacrylates Mw = 100 g/mol) (3 marks)...