Diels-Alder Reaction Teacher : Prof. Guey-Sheng Liou Advisor : Prof. Ching-I Huang Speaker : Wei-Ting Li Date : 2014.1.3 N. Yoshie, Encyclopedia of Polymer Science and Technology. Diels-Alder Polymers: 1-18 (2013)

Outline Diels-Alder Reaction Diels-Alder Polymerization Furan and Maleimide Anthracene and Maleimide Functions of Diels-Alder Polymer Reversibility Healing Polymers Conclusion

Retro Diels-Alder Reaction [4+2] Cycloaddition Otto Diels 1876~1954 Germany Nobel Prize in Chemistry (1950) Kurt Alder 1902~1958 Germany Nobel Prize in Chemistry (1950) Retro Diels-Alder Reaction Diels, O. .; Alder, K. . (1928). "Synthesen in der hydroaromatischen Reihe". Justus Liebig's Annalen der Chemie 460: 98–122.

Diels-Alder Reaction ΔH < 0 ΔS < 0 ΔG = ΔH – TΔS < 0 Via a one-step, cyclic transition state, with no intermidiates generated. Converts two pi bonds into two sigma bonds. Good control over regio- and stereochemical properties. Favor spontaneous at low temperature. ΔG = ΔH – TΔS < 0 Diels, O. .; Alder, K. . (1928). "Synthesen in der hydroaromatischen Reihe". Justus Liebig's Annalen der Chemie 460: 98–122.

Mechanism Electron withdrawing groups Electron donating groups L.G. Wade, Jr. Organic Chemistry

Examples Electron withdrawing groups Electron withdrawing groups Electron donating groups Electron donating groups Electron withdrawing groups L.G. Wade, Jr. Organic Chemistry

Orbital Symmetry Symmetry-allowed L.G. Wade, Jr. Organic Chemistry

Stereochemical Requirements of the Transition State s-cis of the diene Syn addition The endo rule L.G. Wade, Jr. Organic Chemistry

s-cis Conformation of the Diene Cyclopentadiene is fixed in the s-cis conformation, it is highly reactive. L.G. Wade, Jr. Organic Chemistry

Syn Stereochemistry trans trans trans cis L.G. Wade, Jr. Organic Chemistry

The Endo Rule L.G. Wade, Jr. Organic Chemistry

Unsymmetrical Reagents 1,4-product 1,2-product L.G. Wade, Jr. Organic Chemistry

Outline Diels-Alder Reaction Diels-Alder Polymerization Furan and Maleimide Anthracene and Maleimide Functions of Diels-Alder Polymer Reversibility Healing Polymers Conclusion

Diels-Alder Polymerization Researchers have focused on the diene-dienophile combination. Ease of reactant preparation. Reaction rate. Equilibrium constant at room temperature. Temperaure above which the retro Diels-Alder reaction. Representative diene-dienophile combinations for polymer synthesis Furan and Maleimide Anthracene and Maleimide Cyclopentadiene Dithioester and Dienes N. Yoshie, Encyclopedia of Polymer Science and Technology. Diels-Alder Polymers: 1-18 (2013)

Furan and Maleimide Aromatization Extensively used in synthesizing functional polymers owing to its thermoreversibility. Although the relatively low thermal stability, reversibility at moderate temperature makes the reaction very attractive as a source of a dynamic bond. General concern for environmental sustainability has stimulated much research toward green chemistry, including production of polymers from renewable resources. Aromatization A. Gandini, Prog. Polym. Sci. 38, 1–29 (2013).

Linear Polymerization Furan and Maleimide Linear Polymerization A. Gandini, Prog. Polym. Sci. 38, 1–29 (2013).

Non-linear Polymerization Furan and Maleimide Dendrimer Network Polymers A. Gandini, Prog. Polym. Sci. 38, 1–29 (2013).

Furan and Maleimide Cross-linking 80℃ A. Gandini, Prog. Polym. Sci. 38, 1–29 (2013).

Anthracene and Maleimide Thermally more stable than the furan/maleimide Diels-Alder adduct. The thermal stability also results in a higher rate of the cycloaddition. Simple reaction conditions, high yield, and high selectivity, make the reaction valuable in polymer synthesis. More often used in click reactions because of the thermal stability of the resultant products. N. Yoshie, Encyclopedia of Polymer Science and Technology. Diels-Alder Polymers: 1-18 (2013)

Anthracene and Maleimide Multiarm star terpolymer Three-arm star block copolymer ABC-type linear terpolymer H. Durmaz, A. Sanyal, G. Hizal, and U. Tunca, Polym. Chem. 3, 825–835 (2012).

Anthracene and Maleimide H-shaped quintopolymer Cyclic block copolymer Heterograft terpolymer H. Durmaz, A. Sanyal, G. Hizal, and U. Tunca, Polym. Chem. 3, 825–835 (2012).

Anthracene and Maleimide Dendronized Graft B. Gacal, H. Durmaz, M. A. Tasdelen, G. Hizal, U. Tunca, Y. Yagci, and A. L. Demirel, Macromolecules 39, 5330–5336 (2006). M. Tonga, N. Cengiz, M. M. Kose, T. Dede, and A. Sanyal, J. Polym. Sci., Part A: Polym. Chem. 48, 410–416 (2010).

Outline Diels-Alder Reaction Diels-Alder Polymerization Furan and Maleimide Anthracene and Maleimide Functions of Diels-Alder Polymer Reversibility Healing Polymers Conclusion

Reversibility The thermoreversibility for Diels-Alder polymers to function as smart materials. Repeatable bonding/debonding in Diels-Alder polymers confers stimuli-responsive properties to gels, organic-inorganic hybrids, and core-cross-linked micelles, and provides a route to surface modification. Reworkability and recyclability of thermosets, adhesives, and foams. The Diels-Alder network polymers has been applied to lithiography. Nanoporous films were successfully fabricated by combining microphase separation in block copolymers and retro Diels-Alder reaction. N. Yoshie, Encyclopedia of Polymer Science and Technology. Diels-Alder Polymers: 1-18 (2013)

Healing Polymers N. Yoshie, Encyclopedia of Polymer Science and Technology. Diels-Alder Polymers: 1-18 (2013)

Outline Diels-Alder Reaction Diels-Alder Polymerization Furan and Maleimide Anthracene and Maleimide Functions of Diels-Alder Polymer Reversibility Healing Polymers Conclusion

Conclusion Some Diels-Alder reactions are thermally reversible. Enthalpically favorable forward cycloaddition proceeds at a low temperature, whereas the opposite cycloreversion proceeds at a moderate to high temperature. Recently, the Diels-Alder reaction has been rerecognized as a member of the click-chemistry family. Because of the simple reaction condition, high yield, and high selectivity. The Diels-Alder reaction is extensively used in polymer chemistry. Linear, network, and hyperbranched polymers as well as polymers with unique architectures have been prepared from monomers and prepolymers containing a diene and a dienophile. Diels-Alder click chemistry is a powerful tool for synthesizing polymers with various advanced architectures (e.g., block and graft copolymers, star polymers, telechelic polymers, dendrimers, and dendronized polymers). N. Yoshie, Encyclopedia of Polymer Science and Technology. Diels-Alder Polymers: 1-18 (2013)

Thanks for your attention.