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Questions and Answers
What type of polymerization is characterized by the absence of chain termination due to proton loss or combination?
What is required for anionic polymerization to occur?
Why do alkenes require electron-withdrawing substituents for anionic polymerization?
What is the initiator in anionic polymerization?
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What is the result of chain combination or disproportionation in radical polymerization?
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What is the monomer in Super Glue?
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What initiates the polymerization reaction in Super Glue?
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What is the result of anionic polymerization in Super Glue?
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What is the mechanism of polymerization of epoxides when the initiator is a nucleophile?
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What is the process of hardening rubber by introducing cross-links between polymer chains?
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What type of polymerization is used to produce synthetic rubbers from dienes other than isoprene?
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What is the term for polymers formed from a single type of monomer?
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What is the result of the reaction between the nucleophile and the epoxide in anionic polymerization?
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What type of copolymer has a random distribution of monomers?
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What is the type of polymerization that involves the opening of epoxide rings?
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What is the term for the process of creating a polymer from two or more different monomers?
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What is the characteristic of condensation polymers?
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Which of the following is NOT a class of step-growth polymers?
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What is the characteristic of nylon 6?
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What is the starting material for the synthesis of nylon 6?
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What is the characteristic of nylon 66?
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What is the characteristic of Dacron?
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What is the characteristic of Kodel polyester?
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What is the characteristic of epoxy resins?
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Study Notes
Ring-Opening Polymerizations
- Epoxides undergo chain-growth polymerization, which can occur through an anionic mechanism if the initiator is a nucleophile, or through a cationic mechanism if the initiator is a Lewis acid.
- In an anionic mechanism, the nucleophile attacks the less sterically hindered carbon of the epoxide.
Polymerization of Dienes
- Natural rubber is a polymer of 2-methyl-1,3-butadiene (isoprene).
- Synthetic rubbers can be made by radical polymerization of dienes other than isoprene.
- A problem with natural and synthetic rubbers is that they are soft and sticky, but they can be hardened by vulcanization (heating with sulfur), which causes cross-linking of the separate polymer chains through disulfide bonds.
Copolymers
- Copolymers are formed from two or more different monomers.
- Both chain-growth polymers and step-growth polymers can be copolymers.
- There are four types of copolymers: alternating, block, random, and graft copolymers.
Condensation Polymers (Step-Growth Polymers)
- Condensation polymers are formed by the intermolecular reaction of molecules with a functional group at each end.
- A small molecule, such as H2O, alcohol, or HCl, is often lost during the reaction.
- Condensation polymers can be formed from a single compound with two different functional groups or from two different compounds.
Classes of Step-Growth Polymers
- Polyamides
- Polyesters
- Epoxy Resins
- Polyurethanes
Polyamides
- Nylon 6 is a step-growth polymer formed from a monomer with two different functional groups.
- The carboxylic acid group of one monomer reacts with the amino group of another monomer to form an amide.
- Nylon 6 is formed from the polymerization of 6-aminohexanoic acid, which contains six carbons.
- Nylon 66 is formed from the reaction of adipoyl chloride and 1,6-hexanediamine.
Polyesters
- Polymers containing many ester groups.
- Dacron is a common polyester formed by the transesterification of dimethyl terephthalate with ethylene glycol.
- Kodel polyester is formed by the transesterification of dimethyl terephthalate with 1,4-di(hydroxymethyl)cyclohexane.
Epoxy Resins
- They are the strongest adhesives known, with extensive cross-linking.
- They adhere to almost any surface and are resistant to solvents and high temperatures.
Anionic Polymerization (Living Polymers)
- The initiator is a nucleophile that reacts with the monomer to form an anion propagating site.
- Nucleophilic attack on an alkene requires a very good nucleophile and an alkene with an electron-withdrawing substituent.
- Living polymers are common in anionic polymerization because the chains cannot be terminated by proton loss or chain combination or disproportionation.
- Examples of alkenes that undergo anionic polymerization include methyl α-cyanoacrylate (Super Glue).
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Description
Learn about condensation polymers, also known as step-growth polymers, and how they are formed through intermolecular reactions with functional groups.
