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Organic Chemistry 6 th Edition Paula Yurkanis Bruice

Chapter 29 Synthetic Polymers. Organic Chemistry 6 th Edition Paula Yurkanis Bruice. A polymer is a large molecule made by linking together repeating units of small molecules called monomers:. Chain-growth polymers, also known as addition polymers, are made by chain reactions:.

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Organic Chemistry 6 th Edition Paula Yurkanis Bruice

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  1. Chapter 29 Synthetic Polymers Organic Chemistry 6th Edition Paula Yurkanis Bruice

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

  3. Chain-growth polymers, also known as addition polymers, are made by chain reactions:

  4. Step-growth polymers, also called condensation polymers, are made by combining two molecules while removing a small molecule:

  5. Chain-Growth Polymers Chain-growth polymers proceed by one of three mechanisms: • Radical polymerization • Cationic polymerization • Anionic polymerization

  6. Radical Polymerization

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

  8. Chain-growth polymerization of monosubstituted ethylenes exhibits a marked preference for head-to-tail addition:

  9. Head-to-tail addition of a substituted ethylene results in a polymer in which every other carbon bears a substituent:

  10. Head-to-tail addition is favored for steric reasons. • Groups that stabilize radicals also favor head-to-tail • addition.

  11. Branching of the Polymer Chain

  12. Branched polymers are more flexible

  13. Cationic Polymerization

  14. The carbocation intermediates formed during polymerization can undergo rearrangement to form more stable carbocations:

  15. Monomers with electron-donating substituents readily undergo cationic polymerization:

  16. Anionic Polymerization The initiator is a nucleophile, generally a strong base

  17. Nonterminated chains are called “living polymers” and remain active until they are “killed.”

  18. An Example of Anion Polymerization

  19. What Determines the Mechanism? • Alkenes with substituents that can stabilize radicals • readily undergo radical polymerization. • Alkenes with electron-donating substituents that can • stabilize cations undergo cationic polymerization. • Alkenes with electron-withdrawing substituents that can stabilize anions undergo anionic polymerization. • Some alkenes undergo polymerization by more than one mechanism.

  20. Ring-Opening Polymerization

  21. Stereochemistry of Polymerization Substituents on the same side: Substituents regularly alternate on both sides: Substituents in an atactic polymer are randomly oriented

  22. Long, unbranched polymers with either isotactic or the syndiotactic configuration can be prepared using an aluminum–titanium initiator (Ziegler–Natta catalyst):

  23. Polymerization of Dienes

  24. Synthesis of Synthetic Rubber

  25. The product resulting from polymerization of different monomers is called a copolymer:

  26. Four Types of Copolymers

  27. Progress of a Step-Growth Polymerization

  28. Nylon 6 is an example of a step-growth polymer formed by a monomer with two different functional groups:

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

  30. Polyesters are step-growth polymers in which the monomer units are joined together by ester groups:

  31. Polyesters with two ester groups bonded to the same carbon are known as polycarbonates:

  32. Epoxy resins are the strongest adhesive known:

  33. A urethane (carbamate) is a compound that has an OR group and an NHR group bonded to the same carbonyl compound:

  34. Thermosetting Polymers Very strong and rigid materials can be obtained by cross-linking.

  35. Oriented Polymers These polymers are stronger than steel and can conduct electricity

  36. Biodegradable Polymers These polymers can be broken into small molecules by microorganisms The cyclic dimer of lactic acid undergoes ring-opening polymerization to afford a high-molecular-weight polylactide: Polyhydroxyalkanoates (PHAs) are condensation polymers of 3-hydroxycarboxylic acids:

  37. Other Polymers • Thermoplastic polymers have both ordered crystalline regions and amorphous, noncrystalline regions. • Elastomers are polymers that stretch and then revert to the original shape. • Plasticizer is an organic compound that is added to a polymer to make it more flexible.

  38. Bisphenol A linker Bisphenol A may be hazardous to humans Dental Restorative Resin Components Photo-curable resin used by dentists to restore decayed teeth

  39. Photo-Initiator Components

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