Polymer ionic 2018 part 1.pdf - Ionic Polymerization 离子聚合 Prof Cyrille Boyer Ionic Polymerisations – A Subclass of Chain Polymerisations •

Polymer ionic 2018 part 1.pdf - Ionic Polymerization...

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Ionic Polymerization Prof. Cyrille Boyer
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2 Ionic Polymerisations – A Subclass of Chain Polymerisations “A” is a typical chain growth curve Free radical, uncontrolled cationic and anionic polymerizations “B” is typical for a “living” process Protein synthesis Non-terminating ionic processes Some LFRP “C” is a typical step growth curve A B C
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3 Ionic Polymerisations – A Subclass of Chain Polymerisations C + R R 1 B - F F F OH C R R 1 Li + C - R R 1 cationic polymerisation anionic polymerisation radical polymerisation The nature of R and R 1 determines if cationic or anionic polymerisation is possible Whether the group(s) are electron-withdrawing or electron- donating
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4 Polymerisation Routes for Various Monomer Types Monomer Radical Cationic Anionic Ethylene 1-Alkyl olefins 1,1 Dialkyl olefins 1,3-Dienes Styrenes Halogenated olefins Vinyl esters (Meth)acrylates (Meth)acrylonitrile (Meth)acrylamide Vinyl ethers N -Vinyl carbazole N -Vinyl pyrrolidone Aldehydes, ketones Odian, G. Principles of Polymerization, 4 th Ed. 2004 John Wiley & Sons; Hoboken, NJ; pp 200. Almost all monomers containing the carbon–carbon double bond undergo radical polymerization, while ionic polymerizations are highly selective
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5 Cationic polymerization is essentially limited to those monomers with electron-releasing substituents such as alkoxy, phenyl, vinyl, and 1,1-dialkyl. Anionic polymerization takes place with monomers possessing electron-withdrawing groups such as nitrile, carbonyl, phenyl, and vinyl. The selectivity of ionic polymerization is due to the very strict requirements for stabilization of anionic and cationic propagating species Polymerisation Routes for Various Monomer Types
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6 General Similarities For Anionic and Cationic Polymerisations Polymerisation is dependent on an ion pair – The ion of interest on the chain end Carbanion for anionic polymerisation Carbocation for cationic polymerisation – The counterion ensures the system is electronically neutral Counterion charge stability, size, neucleo- or electrophilicity, and solvating ability all effect the polymerisation kinetics
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General Similarities For Anionic and Cationic Polymerisations Four distinct types of ion pairs Covalent species : chemical bond between ion species Contact ion pair : covalent bond broken, but virtually no charge separation Solvent-separated ion pair : solvent molecules separate the charges, but they are still close Free ion pairs : highly solvated, both species free to diffuse through the system
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8 General Reaction Conditions and Considerations Reaction temperatures typically range from room temp.
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