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Case Western Reserve University

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1 Case Western Reserve University
Chapter 28 Synthetic Polymers Organic Chemistry 4th Edition Paula Yurkanis Bruice Irene Lee Case Western Reserve University Cleveland, OH ©2004, Prentice Hall

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 by removing a small molecule

5 Chain-Growth Polymers
Chain-growth polymers proceed by one of three mechanisms: radical polymerization cationic polymerization anionic polymerization


7 Radical Polymerization



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

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

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

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



16 Branching of the Polymer Chain

17 Branched polymers are more flexible

18 Cationic Polymerization
the alkene monomer reacts with an electrophile



21 The carbocation intermediates formed during
polymerization can undergo rearrangement

22 Monomers that are best able to undergo cationic
polymerization are those with electron-donating substituents

23 Anionic Polymerization
Nonterminated chains are called living polymers The chains remain active until they are killed



26 Ring-Opening Polymerization


28 Stereochemistry of Polymerization
substituents on the same side substituents regularly alternate on both sides

29 Long, unbranched polymers can be prepared using an
aluminum–titanium initiator (Ziegler–Natta catalyst)


31 Polymerization of Dienes

32 Synthesis of Synthetic Rubber

33 The product resulting from polymerization of different
monomers is called a copolymer

34 Four Types of Copolymers

35 Progress of a Step-Growth Polymerization

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

37 The incorporation of aromatic rings into polymers
improves the physical strength of the polymers


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

40 Polyesters with two ester groups bonded to the same
carbon are known as polycarbonates

41 Epoxy resins are the strongest adhesive known

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

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

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

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

46 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

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