7. Cationic polymerization & ROP

Question 1

Which type of polymerization will be driving by entropy?

Answer 1

Polymerization of polysiloxans as the polymer is actually less restricted than the monomer.

Question 2

Which ring size cannot generally be polymerized?

Answer 2

The more strained the ring, the more likely it is to be polymerized

Question 3

Can substituted tetrahydrofuranes be polymerized?

Answer 3

Yes, as they are highly strained.

Question 4

Which mechanism is most commonly seen in ROP?

Answer 4

Anionic, cationic and CCC are all seen in ROP, although cationic a bit less than the other two. Each type is however used for specific reactions.

Question 5

Which mechanism gives highest molecular weight nylon 6?

Answer 5

Anionic ROP

Question 6

Which type of monomer substituent is preferred in cationic polymerization?

Answer 6

Electron donating groups, such as ethers.

Question 7

Of the following, which are coinitiators? a) Lewis acids (AlCl3 or BF3), b) H2O, or c) H2SO4 or H3PO4.

Answer 7

a) Lewis acids (AlCl3 or BF3)

Question 8

Of the following, which are initiators? a) Lewis acids (AlCl3 or BF3), b) H2O, or c) H2SO4 or H3PO4.

Answer 8

b) H2O, and c) H2SO4 or H3PO4?

Question 9

Which is the most reactive styrene monomer in cationic polymerization: 4-chlorostyrene, styrene, 2-methoxystyrene, 4-methylchlorostyrene, 4-methylstyrene, 2-methylstyrene, or 4-methoxystyrene?

Answer 9

4-methoxystyrene. The most donating substituent, will stabilize the cation the best. In addition, where there is a choice, also the least sterically hindered would be faster.

Question 10

Which is the most industrially relevant polymer made by cationic polymerization? Polystyrene, poly(4-methoxystyrene), poly(isoprene), poly(isobutylene), or poly(isobutylene-co-isoprene)?

Answer 10

Poly(isobutylene-co-isoprene). Butyl rubber - a copolymer of isobutylene and isoprene is the commercially most important product produced by cationic polymerization.