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Odian Book Chapter 3-15, 5-3

Odian Book Chapter 3-15, 5-3. Living Polymerization (II) by Ru-Ke Bai. Department of Polymer Science and Engneering University of Science and Technology of China. A. B. C. Block copolymers can be prepared by sequential addition of monomers. M n. ln[M] 0 /[M] t. PDI. Time.

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Odian Book Chapter 3-15, 5-3

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  1. Odian Book Chapter 3-15, 5-3

  2. Living Polymerization (II)byRu-Ke Bai Department of Polymer Science and Engneering University of Science and Technology of China

  3. A B C Block copolymers can be prepared by sequential addition of monomers. Mn • ln[M]0/[M]t PDI Time A Brief Review • What is living polymerization? • No termination • No chain transfer • What are the major criteria for living polymerization? Living polymerization is a good tool for the preparation of block copolymers.

  4. Rankings of Anions… How to characterize the reactivity of a propagating anion?

  5. Propagating Anions pKa of conjugate acid of prop.chain end 42 25 25 20

  6. Propagating Anions pKa of conjugate acid of prop.chain end 16-18 10-12 11-13

  7. Initiators Super glue most nucleophilic Reactivity Least nucleophilic

  8. Microstructure of Dienes Four different microstructures in polyisoprene cis 1-4 isomer (natural rubber) trans 1-4 isomer 1-2 isomer 3-4 isomer cis-1,4 favored in hydrocarbon solvents

  9. Can MMA be polymerized via living process ? Side reactions 1) 2) 3)

  10. PMMA via Living Pzn • PMMA homopolymer • Can not use BuLi directly • Make new initiator (use 1,1-diphenylethylene) 1,1-diphenyl hexyl lithium (DPHL) • Sterically hindered • resonant stabilization

  11. PMMA via Living Pzn

  12. Ex.A-A-A-A-A-A-B-B-B-B-B-B Block Copolymers • Definition: Macromolecules consisting of homogenous segments made from different monomers (usually two or three different monomers).

  13. Ex. PS-b-PI Ex: PS-g-PI Some Basic Diblock Copolymer Architectures • Linear Graft Star

  14. Microphase Separation • Most polymers are immiscible

  15. Block Copolymer Uses Thermoplastic Elastomer Common Elastomer Poly(cis-1,4-butadiene) SBS (PS-PB-PS) Physical crosslinking Thermal reversibility Can process it repeatedly Sulfur Crosslinking heating cooling Chemical rosslinking Thermal irreversibility Can’t process it repeatedly

  16. = packing parameter, v = hydrophobic volume, a = interfacial area at the hydrophobe-hydrophile/water interface, = the chain length normal to the surface per molecule. Self-Assembly of Block CopolymerPolym. Chem. 2011, 2, 1018–1028. PB-b-PEO PS-b-PAA cryoTEM micrographs TEM micrographs vesicles Cylindrical micelles Spherical micelles

  17. Dispersion of Carbon Nanotubes by Block Copolymer • The study of Single-Walled Carbon Nanotubes (SWNT) composite materials • has been hindered by the poor solubility and processibility of SWNTs. • PS-b-PAA has been used to stabilize SWNT and prevent their aggregation. • The micelle-encapsulated SWNTs are compatible with a wide variety of • solvent and polymer matrices, which can be used to produce carbon • nanotube materials. Kang, Y. and Taton, A. T. J. Am. Chem. Soc. 2003, 125(19) 5650 – 5651.

  18. Synthesis of Block Copolymers • A-B diblock or A-B-A triblock copolymers • styrene pKa= 42 • epoxide pKa= 16-18 • cross over from ethylene oxide not possible same pKa, same reactivity; no problem any order of addition, can cross over back & forth 2) ethylene oxide/styrene copolymers

  19. Styrene-MMA Block Copolymers 3) Styrene & MMA • Then MMA, but can’t do sequential addition • Styrene

  20. Styrene-MMA Block Copolymers • Styrene • cap w/ 1,1-diphenylethylene (DPE) • MMA @ -78 oC, THF

  21. PMMA-PS-PMMA • DFI to initiate styrene • Diphenyl ethylene to initiate MMA segment • Add MMA

  22. X = Y = Synthesis of Regular Star PS by Iterative Methodology Using DPE Functionality 1st Iteration 1 1st Iteration ( = ) (= ) ( = ) 1st Iteration 2st Iteration 3st Iteration 4st Iteration 5st Iteration

  23. Synthesis of Asymmetric Star-Branched Polymers by Iterative Methodology 1

  24. Synthesis of Asymmetric Star-Branched Polymers by Iterative Methodology 1

  25. Synthesis of Star-Branched PS with up to 63 Arms by Iterative Methodology 5

  26. Branched Polymers with Complex Architectures Macromol. Rapid Commun. 2010, 31,1031-1059. star-linear-star star-on-linear (dendrimer)-linear-(dendrimer) (dendrimer)-on-linear graft-on-graft graft-on-star star-on-graft star-on-star

  27. Reversible termination Terminology: “controlled/living”, “pseudo-living”, “quasi-living”, and “reversible deactivation radical polymerization” Living/Controlled Free Radical Polymerization • How to perform a living free radical polymerization? • Anionic polymerization Radical polymerization • kt = 0 kt = 106-108 • Ri > Rp Ri < Rp

  28. Stable Free-Radical Polymerization (SFRP) TEMPO: 2,2,6,6-tetramethyl-1-piperidinoxyl • Radical was formed differently • Reversible chain termination! M. K. Georges, et al, Macromolecules, 26, 2987( 1993).

  29. Atom Transfer Radical Polymerization (ATRP) X = Br , Cl Components: Monomer: A wide variety of monomers Initiator: R-X, X = Br and Cl Catalyst: Cu, Fe, and Ru etc. Ligand: Bipyridine ect. • Radical was formed differently • Reversible chain termination! Wang, J. S.; Matyjaszewski, K. Macromolecules 1995, 28, 7901-7910.

  30. Reversible Addition-Fragmentation Chain Transfer (RAFT) • Normal radical initiators (AIBN, etc.) • Reversible chain transfer! Rizzardo, E., et al. Macromolecules 1998, 31, 5559-5562.

  31. Advantages of Living Free Radical Polymerization Radical polymerization Anionic polymerization • A variety of monomers, including • the monomers with OH, COOH groups; • Perform in bulk, solution, emulsion, • and suspension systems; • Simple and inexpensive. • Styrenes, dienes, and methacrylates; • Perform in solution under unaerobic • and anhydrous conditions; • Complex and expensive. A powerful platform for preparing a variety of well-defined polymers

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