Addition Polymers and Their Uses
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Questions and Answers

What is the minimum number of steps required for an addition polymerization reaction?

  • Two
  • One
  • Four
  • Three (correct)

    • What is the role of an initiator in radical polymerization?

  • To break homolytically into radicals (correct)
  • To oxidize the monomer
  • To react with the monomer
  • To terminate the polymer chain growth

    • What is the propagating site in radical polymerization?

  • The monomer unit
  • The end of the polymer chain
  • The unpaired electron (correct)
  • The start of the polymer chain

    • What happens when two chains combine at their propagating sites in termination steps?

    <p>Chain combination occurs</p> Signup and view all the answers

    How many subunits are added to the chain in each propagation step?

    <p>One</p> Signup and view all the answers

    What is the result of disproportionation in termination steps?

    <p>One chain is oxidized to an alkene and the other reduced to an alkane</p> Signup and view all the answers

    How many mechanisms of polymerization are mentioned in the text?

    <p>Three</p> Signup and view all the answers

    What is the role of the monomer in radical polymerization?

    <p>To react with the initiator</p> Signup and view all the answers

    What type of shift can lead to a more stable carbocation during cationic polymerization?

    <p>1,2-hydride shift</p> Signup and view all the answers

    What is the characteristic of the initiator in anionic polymerization?

    <p>A very good nucleophile</p> Signup and view all the answers

    What is the purpose of substituents in the monomer during cationic polymerization?

    <p>To stabilize the positive charge at the propagating site</p> Signup and view all the answers

    What type of polymer is formed during anionic polymerization?

    <p>Living polymer</p> Signup and view all the answers

    What is the characteristic of the propagating site in unrearranged cationic polymerization?

    <p>A secondary carbocation</p> Signup and view all the answers

    What is the reason for the nucleophilic attack not occurring readily on an alkene?

    <p>Alkenes are electron rich</p> Signup and view all the answers

    What is the result of a 1,2-hydride shift during cationic polymerization?

    <p>A more stable tertiary carbocation is formed</p> Signup and view all the answers

    Why must the alkene contain electron-withdrawing substituents in anionic polymerization?

    <p>To decrease the electron density of the double bond</p> Signup and view all the answers

    What is the primary mechanism of formation of nylon 6?

    <p>Reaction of carboxylic acid group with amino group to form an amide</p> Signup and view all the answers

    Which of the following polyesters is formed by the transesterification of dimethyl terephthalate with 1,4-di(hydroxymethyl)cyclohexane?

    <p>Kodel</p> Signup and view all the answers

    What is the characteristic feature of epoxy resins?

    <p>They are extensively cross-linked systems</p> Signup and view all the answers

    What is the functional group present in polyurethanes?

    <p>Urethane</p> Signup and view all the answers

    What is the monomer requirement for the formation of nylon 6?

    <p>A monomer with two different functional groups</p> Signup and view all the answers

    What is the name of the starting material used for the synthesis of nylon 6?

    <p>ε-caprolactam</p> Signup and view all the answers

    What is the characteristic feature of nylon 66?

    <p>It is formed from two different bifunctional monomers</p> Signup and view all the answers

    What is the purpose of the hardener in epoxy cement?

    <p>To react with the prepolymer to form a cross-linked polymer</p> Signup and view all the answers

    Study Notes

    Addition Polymers

    • Chain-growth polymerization proceeds by three mechanisms: radical, cationic, and anionic polymerization.
    • Each mechanism has three distinct steps: initiation, propagation, and termination.

    Radical Polymerization

    • Initiation step: a radical initiator is added to the monomer to generate the radical that starts the growth of the polymer chain.
    • Propagation steps: the monomer radical reacts with another monomer, converting it into a radical, and the process is repeated.
    • Termination steps: may occur by chain combination or disproportionation.

    Cationic Polymerization

    • Initiation step: a chain-initiating step occurs.
    • Propagation steps: chain-propagating steps occur.
    • Termination step: the carbocation intermediates undergo rearrangement by either a 1,2-hydride shift or a 1,2-methyl shift.
    • The best monomers have substituents that stabilize the positive charge at the propagating site.

    Anionic Polymerization

    • The initiator is a nucleophile that reacts with the monomer to form an anion propagating site.
    • The alkene must contain electron-withdrawing substituents to decrease the electron density of the double bond.

    Classes of Step-Growth Polymers

    • Polyamides
    • Polyesters
    • Epoxy Resins
    • Polyurethanes

    Polyamides

    • Nylon 6 is an example of a step-growth polymer formed from a monomer with two different functional groups.
    • Nylon 6 is formed from the polymerization of 6-aminohexanoic acid, which contains six carbons.
    • The starting material for the synthesis of nylon 6 is ε-caprolactam.
    • Nylon 66 is formed by two different bifunctional monomers—adipoyl chloride and 1,6-hexanediamine.

    Polyesters

    • Polymers containing many ester groups.
    • Dacron is made 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 and are extensively cross-linked systems.
    • Epoxy cement is consisting of a low-molecular-weight prepolymer and a hardener that react when mixed to form a cross-linked polymer.

    Polyurethanes

    • A urethane is a compound that has an OR group and an NHR group bonded to the same carbonyl carbon.

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    Description

    This quiz covers the mechanisms of addition or chain-growth polymerization, including radical, cationic, and anionic polymerization, as well as the three distinct steps involved in each mechanism.

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