Chemistry Reference
In-Depth Information
Review Questions
Section 4.1
1. Explain the differences and similarities m anionic and cationic chain growth polymerizations.
Section 4.2
1. Write chemical equations for cationic initiation, propagation, and termination steps and show what
the kinetic expressions are.
2. Write the cationic kinetic expression for the degree of polymerization and the rate of propagation.
3. Repeat questions 1 and 2 for anionic polymerizations.
Section 4.3
1. Explain what is meant by the expression that initiation in cationic polymerization results from
transposition of either one or two electrons. What type of initiating species is involved?
2. Summarize the initiation process in cationic chain-growth polymerization.
3. Show by chemical equations the initiation process by protonic acids, by Lewis acids complexed
with water and or with alkyl halides.
4. What is the proposed mechanism of initiation of polymerization, by the Lewis arid like aluminum
chloride or bromide through an auto ionization process?
5. What are the several proposed mechanisms of initiations by stable cations?
6. Explain how some cationic polymerizations can be initiated by metal alkyls and substances that
generate cations.
7. Show the mechanism of one electron transposition initiation with chemical equations based on a
free-radical oxidation by diphenyliodonium hexafluorophosphate (let the source of the free-
radicals be photo decomposition of methyl benzoin ether).
8. Discuss briefly the role of charge transfer complexes in initiations of cationic polymerizations.
9. What is the mechanism of electro initiation of cationic polymerization?
10. How does the tightness of the ion pairs affect propagation in cationic polymerization?
11. What is the mechanism of chain growth with a tight ion pairs in cationic polymerization?
12. Discuss the Kunitake and Takanabe mechanism for steric control in homogeneous cationic
polymerizations.
13. What
is
the Nakano et al. mechanism for
steric control
in heterogeneous cationic
polymerizations?
14. What is pseudo-cationic polymerization? Explain and illustrate on polymerization of styrene
initiated by perchloric acid.
15. Describe and give examples of chemical reactions of isomerization polymerization where the
propagation is accompanied by bond or electron rearrangement.
16. Give two examples of chemical reactions where the propagation in isomerization polymerization
is accompanied by migration of one or more atoms.
17. Illustrate the termination reactions in cationic polymerizations.
18. What are the important aspects of living cationic polymerization? Can you give examples?
