1. What Are the 2 Major Classes of Synthetic Polymers?

CLAS – Chem 109C – Chapter 27 Answer Key

1. What are the 2 major classes of synthetic polymers?

1) Chain growth ⇒ made by addition reactions using alkenes, conjugated dienes or epoxides as monomers to make alkanes, polyalkenes or polyethers respectively – these chains are built form one end to the other

2) Step growth ⇒ made by condensation reactions to make polyamides, polyesters or polyurethanes – these chains are built in random directions

2. What are the 3 subclasses (or mechanisms) of chain-growth polymers?

1) anionic

2) cationic

3) radical

3. Describe the 3 phases of chain-growth polymerization.

Initiation, propagation and termination

4. What is an ideal initiator and monomer for each of the 3 subclasses of chain-growth polymerization?

1) anionic⇒ super strong base initiators (ex RLi) and monomers with electron withdrawing groups

2) cationic⇒ strong Lewis acid initiators (ex BF3) and monomers with electron donating groups

3) radical⇒ peroxide (R-O-O-R) or azo (R-N=N-R) initiators and monomers that can have resonance or hyperconjugation with the radical

5. Draw a short segment of polymer that would form from the following monomers:

a. styreneb. methyl methacrylatec. 2-ethyloxirane

5. What monomer would you use to synthesize the following polymers?

⇒

n⇒

d. –CH2CH(CH3)OCH2CH(CH3)OCH2CH(CH3)OCH2CH(CH3)O–⇒

6. Rank the following monomers in order most reactive to least reactive in a cationic polymerization.

a. b.c.

b > a > c

7. Rank the above monomers in order most reactive to least reactive in a anionic polymerization.

c > a > b

8. What does “living polymer” mean?In anionic chain growth the end can be left as an anion and is ready to polymerize

9. What is the monomer and repeating unit for natural rubber?isoprene

10. What is vulcanization and what effect does it have on polymers?vulcanization is the hardening of rubber by adding disulfide bridges between the polymer chains –this can be achieved by heating the polymer in the presence of sulfur

11. What is the role of a plasticizer?A plasticizer is a substance that can be mixed with a polymer to make it more flexible –the molecules disrupt the forces between polymer chains by slipping in between them

12. What’s the difference between isotactic and syndiotactic polymers?Isotactic is when a polymer has all of its chiral centers with the same configuration whereas syndiotactic the configurations alternate

13. What are copolymers and list the 4 types of copolymers? alternating, random, block, graft

14. Draw a short segment of a polymer using the following monomers.

15. What are the monomers for the following polymers?

⇒