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Flashcards

Ionic and living polymerization

Ashlin Deatherage polymer chem English 57 cards

Cards in this deck (57)

  1. 1anionnegative charge
  2. 2cationpositive charge
  3. 3cation polymerization requires that there is anEDG vinyl to double bond
  4. 4the cation initiates by acting as anelectrophile, and is attacked by nucleophile, which are the electrons of double bond
  5. 5anion initiates byacting as a nucleophile, the negative electrons attack the double bond
  6. 6anionic polymerization requiresa vinyl EWG
  7. 7ethers, alcohols, and uncharged amines arevery strong electron donating groups
  8. 8amides and esters areEDG, when attached to the O or N
  9. 9hydrogen and alkyl groups areweak EDG
  10. 10NO2, CN, SO2OH arevery strong EWG
  11. 11when the group is attached by the carbonyl carbons, amides, esters, carboylic acids, and aldehydes act asEWGs
  12. 12what are the 4 routes for cationic initiation1. (H+) arrhenius acid
    2. lewis acid+water (BF3+H2O)
    3. lewis acid +alkyl halide
    4. photoionization
  13. 13photoionization mechanismcheck notes
  14. 14ionic polymerization is more stric monomer wise becausethe monomers must has a structure that stabilizes the active center
  15. 15ionic polymerization has a larger ______ than radical, because ____rate of polymerization, there is a higher concentration of propagating active chains
  16. 16a propagation ionic active center has acounter ion of opposite charge
  17. 17the counter ion influences _____ by its degree of association with the active centerrate of polymerization and the stereochemistry of propagation
  18. 18termination will not happen through ions interacting bcthe ions repel eachother
  19. 19what solvents would not be ideal for ionic polymerizationelectron rich solvents, acid, alcohols, electrophiles, acetone, halogenated solvents
  20. 20ionic polymerization can have ____ rates of polymerization, even at low tempshigh
  21. 21living polymerizationis when termination and transfer are eliminated, can be used to form block copolymers
  22. 22describe heterolytic fissionforms carbocation from lewis acid and alkyl halide, draw mech from notes
  23. 23between temps 0-10 C if isobutane is addedisobutane acts a chain transfer agent and terminates polymerization
  24. 24cationic polymerization preferlower temps
  25. 25draw mechanism for lewis acid and water initiationsee notes
  26. 26draw mechanism for alkyl and aryl cations forming cationic initiatorsee notes
  27. 27living polymerization requires:(3)1. All chains are formed at the beginning of the polymerization
    2. Propagation is continued by all chain simultaneously until all monomers used
    3. no termination
  28. 28Consequences of living polymerization (4)1. Molecular weight is dependent on monomer to initiator ratio and conversion
    2. There's a linear increase in molecular weight with conversion
    3. In the absence of side reactions Weight average and number average molar mass are v similar
    4. At the end of polymerization the chain is still active, and addition of a second monomer will propagate, therefore block copolymer can be formed.
  29. 29living cation polymerization, to control reactivity:(5)1. remove impurities/reactive molecules
    2. Reduce monomer concentration to slow polymerization and reduce exotherms. Beta-proton transfer to monomer and propagation are the competing reactions so lowering the temperature will slow the polymerization and favorite it over transfer
    3. stabilize counterion
    4. Stabilize cation by adding a complexing agent (base)
    5. control active species
  30. 30chain transfer is affected ____ than rate of polymerization by temperaturesmore
  31. 31(CH3)3CCl and Al(CH3)3 react to form anion and carbocation, in the absence of monomer, these two interact and the anion transfers a methyl to the carbocationThis is initiation followed by termination or a polymerization without propagation, the substituents (the methyl) can be changed to make the end group reactive
  32. 32draw mechanism for B-hydrogen transfer to monomerlook at notes
  33. 33ionic termination can happen via1. collapse of ion pair (counterion adds to polymer)
    2. quenching, adding water, alcohol, etc to rxn to donate H or OH
  34. 34carboanionis sp3 w neg charge
  35. 35for anion polymerization, you need avinyl EWG
  36. 36electron withdrawing groupsstabilize propagation anion
  37. 37draw mech for electron transfer initiation and polymerization of styrenenotes
  38. 38Solving effects on ionic reactionsSolvents with high reactive sites which have a high dielectric constants are needed to maintain reactive ionic species
  39. 39for ionic polymerization, you want a solventthat will keep ions completely disassociated
  40. 40cationic polymerization cannot be living becauseits active center is electron deficient, the cation can abstract a proton from the solvent or transfer to monomer
  41. 41Kraton polymersmake triblock polymers by anionic polymerization
  42. 42styrenethermoplastic
  43. 43ethylene butadieneelastomer
  44. 44write out mechanism for ziegler-Natta polymerizationscheck notes
  45. 45for ziegler-Natta polymerization, since the growing chain is coordinated to the metal, the monomers added in the same configuration, and thereforecan crate linear polymers that crystallizes
  46. 46isotacticsame arrangement of R groups, can crystallize
  47. 47syndiotacticalternating conformation of R groups
  48. 48ataticno defined order, amorphous
  49. 49with a high degree of branching,Polymer molecules cannot pack into a crystal lattice well and it's less dense than a highly crystalline polymer
  50. 50HDPE is prepared bycoordination polymerization
  51. 51living polymerization processes (4)1. No termination or transfer
    2. rate of initiation >>>rate of propagation
    3. All growing and start at the same time
    4. All growing ins have equal access to monomer
  52. 52For a living polymerization, the degree of polymerization is affected byinitiator concentration
  53. 53pros of living anionic polymerization (3)Dispersity is low, can make block polymer, high chain in functionality
  54. 54cons of anionic living polymerization (2)Very difficult to do because reaction conditions are strict, limited choice of monomer (needs EWG)
  55. 55'living' radical polymerizationAlso called controlled radical polymerization, low dispersity , wide choice of monomers, friendly reaction conditions, can make block polymers with high chain and functionality
  56. 56living polymerization will createall polymer chains will have the same size and be monodisperse, the degree of polymerization is equal to the ratio of monomer over initiator times the conversion. Allows for the formation of block polymers
  57. 57—

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polymer chem Flashcards on Ionic and living polymerization, created by Ashlin Deatherage on 03/10/2022.
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