1. Chapter 20 Synthetic Polymers

2. A polymer is a large molecule made by linking together repeating units of small molecules called monomers

3. 1. Addition polymers( 加聚物 ), also called chain-growth polymers, are made by chain reactions ( 链反应 ) 2. Condensation polymers( 缩聚物 ), also called step-growth polymers, are made by combining two molecules by removing a small molecule Classification of polymers

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5. 20-1. Addition polymers Chain-growth polymers proceed by one of three mechanisms: (1) radical polymerization (2) cationic polymerization (3) anionic polymerization

6. Some important chain-growth polymers and their uses

7. (1) Radical Polymerization

8. The molecular weight of the polymer can be controlled by a process known as chain transfer

10. Head-to-tail addition is favored for steric reasons Groups that stabilize radicals also favor head-to-tail addition Chain-growth polymerization of monosubstituted ethylenes exhibits a marked preference for head-to-tail addition

11. Examples of alkenes that undergo radical polymerization

12. Some radical initiators

13. Branching of the Polymer Chain Branched polymers are more flexible

14. (2) Cationic Polymerization Chain-initiating step Chain-propagating steps

16. The carbocation intermediates formed during polymerization can undergo rearrangement

17. Monomers that are best able to undergo cationic polymerization are those with electron-donating substituents Examples of alkenes that undergo cationic polymerization

18. (3) Anionic Polymerization Chain-initiating step Chain-propagating steps

19. Examples of alkenes that undergo anionic polymerization Monomers that are best able to undergo anionic polymerization are those with electron- withdrawing substituents

21. Ring-Opening Polymerization

23. Stereochemistry of Polymerization substituents on the same side substituents regularly alternate on both sides isotactic configuration (same side) 全同立构 syndiotactic configuration (both sides) 间同立构 atactic configuration (both sides) 无规立构

24. Long, unbranched polymers can be prepared using an aluminum–titanium initiator (Ziegler–Natta catalyst) Stereochemical control of polymerization

26. Natural and synthetic rubbers Natural rubber is a terpene ( 萜 ) Vulcanization ( 硫化 ): cross-linking of rubbers

27. The product resulting from polymerization of different monomers is called a copolymer Copolymer ( 共聚物 ) Some examples of copolymers and their uses

28. 20-2 Condensation Polymers (resin 树脂 ) Polyamides: Nylon 6 Polyamides 聚酰胺 Polyesters 聚酯 Polycarbonates 聚碳酸酯 Polyurethanes 聚氨酯

29. The incorporation of aromatic rings into polymers improves the physical strength of the polymers

31. Polyesters 聚酯

32. Polycarbonates 聚碳酸酯 热塑聚碳酸酯

33. Epoxy resins are the strongest adhesive known

34. polyurethane 聚氨酯

35. Thermosetting 热固性 Polymers Very strong and rigid materials can be obtained by cross-linking

36. Oriented Polymers These polymers are stronger than steel They can conduct electricity

37. Biodegradable Polymers These polymers can be broken into small segments by enzyme-catalyzed reactions

38. Assignments 26-2, 3, 5, 6