Page 220 - Carrahers_Polymer_Chemistry,_Eighth_Edition

Ionic Chain-Reaction and Complex Coordination Polymerization 183

EXERCISES

1. Describe the contents of the reaction fl ask 10 minutes after the polymerization of (a) reactants
in a stepwise polymerization such as dimethyl terephthalate and ethylene glycol and (b) mono-
mer in chain reactions, such as isobutylene.
2. What is the initiator in the polymerization of isobutylene?
3. What is the general name of the product produced by cationic initiation?
4. What reactant besides the monomer is present in cationic chain propagation reactions?
5. What name is used to describe the negatively charged counterion in cationic chain-reaction
polymerizations?
6. Is a Lewis acid (a) an electrophile or (b) a nucleophile?
7. Is a Lewis base (a) an electrophile or (b) a nucleophile?
8. Why isn’t coupling a preferred termination step in the cationic chain polymerization of pure
monomer?

9. Is the usual configuration of polymers produced by ionic-chain polymerization (a) head-to-tail
or (b) head-to-head.
10. Which condition would be more apt to produce stereoregular polymers in ionic-chain polymer-
izations: (a) high temperature or (b) low temperatures?
11. Name (a) a thermoplastic, (b) an elastomer, and (c) a fiber that is produced commercially by

ionic-chain polymerization.
12. Which technique would you choose for producing a polymer of isobutyl vinyl ether: (a) cationic
or (b) anionic.
13. Which technique would you choose for producing a polymer of acrylonitrile: (a) cationic or
(b) anionic?
14. Which of the following could be used to initiate the polymerization of isobutylene: (a) sulfuric
acid, (b) boron trifluoride etherate, (c) water, or (d) butyllithium?

15. Which of the following could be polymerized by cationic chain polymerization?

OH
CH 3
H C H C H C O CH
2
2
CH 3 O 2 3
N
(a) (b) (c) (d) (e)

16. Which polymer is more susceptible to oxidation: (a) HDPE or (b) PP?
17. When termination is by chain transfer, what is the relationship of average DP and the kinetic
chain length?
18. What would be the composition of the product obtained by the cationic low-temperature poly-
merization of a solution of isobutylene in ethylene?
19. What is the relationship between the rate of initiation to the monomer concentration in ionic-
chain polymerization?
20. What effect will the use of a solvent with a higher dielectric constant have on the rate of prop-
agation in ionic-chain polymerization?
21. How does the rate constant k change as the yield of polymer increases?
p
22. Which will have the higher T value: (a) polystyrene or (b) PIB?
g
23. Which of the following could serve as an initiator for an anionic chain polymerization? (a) AlCl -
3
H O, (b) BF -H O, (c) butyllithium, or (d) sodium metal?
2
3
2
24. What species, in addition to a dead polymer, is produced in a chain transfer reaction with a
macrocarbocation in cationic chain polymerization?

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K10478.indb 183 9/14/2010 3:39:13 PM