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Polymerization Reaction 1 Polymerization Reaction Chain Growth / Condensation Addition Polymerization Polymerization Ionic Polymerization Living Polymerization 2 Chain Growth / Addition Polymerization Free Radical Polymerization Free radical polymerization’s are chain polymerization’s in which each polymer molecules grows by addition of monomer to a terminal free-radical reactive site known as active center. 1 Initiation 2 Propagation 3 Termination 2 Chain Growth / Addition Polymerization Free Radical Polymerization Free radical polymerization’s are chain polymerization’s in which each polymer molecules grows by addition of monomer to a terminal free-radical reactive site known as active center. Initiation 3 Generating free radical from initiator and monomer Initiation 4 Generating free radical from initiator and monomer Propagation 5 Rapid and progressive addition of monomer to the growing chain Termination 6 Destruction of the growth activity of the chain Dispropotional Coupling Termination Termination 7 Coupling / Combination Coupling Two growing polymer chain yield a single polymer molecule terminated at each end by an initiator fragment Coupling Termination 8 Dispropotional CouplingDispropotio While in disproportionation a labile atom (usually hydrogen) is nal transferred from one polymer radical to another Saturated Unsaturated Dispropotional 9 Chain Transfer Initiation CouplingTermination Free Radicalic Ideal Propagation Polymerization (FRP) Chain Transfer Chain Transfer Free Radicalic a growing polymer chain is deactivated or terminated by Polymerization transferring its growth activity to a previously inactive species 10 Chain Transfer To Solvent To Monomer Chain Transfer To Initiator To Polymer 11 Chain Growth / Addition Polymerization Products : Step Growth Polymerization 12 Condensation Polymerization These polymerizations often (but not always) occur with loss of a small byproduct, such as water, and generally (but not always) combine two different components in an alternating structure Nylon 6,6 Polyester (Dacron) Polycarbonat Step Growth Polymerization 13 Condensation Polymerization Condensation polymerization : 1. More slowly than addition polymerization 2. Often requiring heat, and 3. They are generally lower in molecular weight. Step Growth Polymerization 14 Condensation Polymerization By Product / condensation Step Growth Polymerization 15 Condensation Polymerization By Product / condensation Step Growth Polymerization 16 Condensation Polymerization Polymerization Polymerization Reaction Chain Growth / Addition Polymerization Condensation Polymerization Living Ionic Polymerization Polymerization Ionic Polymerization 17 Kind of Chain Reaction Polymerization Ionic polymerizations involve chain carriers or reactive centers that are organic ions or charged organic groups Ionic Polymerization Anionic Polymerization the growing chain end carries a negative charge or carbanions ion Cationic Polymerization the growing chain end with a positive charge or carbonium (carbocation) ion Cationic Polymerization 18 the growing chain end Cationic Polymerization with a positive charge or carbonium (carbocation) ion Monomers with electron-donating groups like isobutylene form stable positive charges and are readily converted to polymers by cationic catalysts Initiation Propagation Termination Chain Transfer Cationic Polymerization 19 the growing chain end Cationic Polymerization with a positive charge or carbonium (carbocation) 1 Initiation ion Any strong Lewis acid like boron trifluoride (BF3) or Friedel–Crafts catalysts such as AlCl3 can readily initiate cationic polymerization in the presence of a cocatalyst like water. During initiation, a proton adds to the monomer to form a carbonium ion Cationic Polymerization 20 the growing chain end Cationic Polymerization with a positive charge or carbonium (carbocation) 2 Propagation ion In the presence of monomer, the chain can grow by the attack of carbocation Cationic Polymerization 21 the growing chain end Cationic Polymerization with a positive charge or carbonium (carbocation) 3 Termination + Chain Transfer ion Cationic Polymerization 22 the growing chain end Cationic Polymerization with a positive charge or carbonium (carbocation) 3 Termination + Chain Transfer ion Cationic Polymerization 22 the growing chain end Cationic Polymerization with a positive charge or carbonium (carbocation) 3 Termination + Chain Transfer ion Anionic Polymerization 23 Anionic Polymerization the growing chain end carries a negative charge or carbanions ion Monomer for Anionic Polymerization Initiation Propagation Anionic Polymerization 24 Anionic Polymerization the growing chain end carries a 1 Initiation negative charge or carbanions ion A classical example is the polymerization of styrene with butyllithium as initiator. Another common initiator is the radical anion of naphthalene, sodium naphthalide. Its cheapness makes it acceptable for industrial application Anionic Polymerization 25 Anionic Polymerization the growing chain end carries a 2 Propagation negative charge or carbanions ion The carbanion now reacts with another monomer molecule in just the same manner as the initiator reacted with the first monomer molecule; another carbanion is generated. This keeps happening, and each time another monomer is added to the growing chain, a new anion is generated allowing another monomer to be added. Anionic Polymerization 26 Anionic Polymerization the growing chain end carries a Living chain end negative charge or carbanions ion No natural termination step, because the chain is mutually repulsive each other Special case, transfer to solvent TERMINATION that is able to Repulsion release proton Anionic Polymerization 27 Anionic Polymerization the growing chain end carries a negative charge or carbanions ion If all the monomer is allowed to react, the degree of polymerisation xn in an anionic polymerisation is adjustable and depends just on two concentrations. It is identical to the monomer (M)-to-initiator (I) ratio if an initiator such as BuLi is used in THF as solvent. Anionic Polymerization 28 Anionic Polymerization the growing chain end carries a negative charge or carbanions ion Advantage Disadvantage 1. Homopolymer with narrow Molecular 1. Require rigorous purification process Weight Distribution (repeated distillation of solvent, degas of 2. Can cop living polymer with specific end H2O and O2, reactor must be cleaned groups under vacuum over night) 3. Able to make sequential monomer 2. Inappropriate for many functional addition monomer especially with labile proton Polymerization Reaction Condensation Polymerization Chain Growth / Addition Polymerization Ionic Polymerization Living Polymerization Living Polymerization 29 Living polymerization doesn’t mean alive in the biological sense. As defined by the International Union of Pure and Applied Chemistry (IUPAC) definition, living polymerization is a chain polymerization from which chain transfer and chain termination are absent Living Polymerization 29 Living polymerization, which has been studied for more than 70 years, can follow anionic, cationic, and radical polymerization mechanisms. Popular atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain transfer (RAFT) are examples of living radical polymerization. Living polymerization allows you to obtain precisely controlled molecular weight and narrow molecular weight distribution, as well as complex polymer architectures. Practical Applications : SMART POLYMER.
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