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21.12 : Anionic Chain-Growth Polymerization: Mechanism

The mechanism for anionic chain-growth polymerization involves initiation, propagation, and termination steps. In the initiation step, a nucleophilic anion, such as butyl lithium, initiates the polymerization process by attacking the π bond of the vinylic monomer. As a result, a carbanion, stabilized by the electron‐withdrawing group, is generated. The resulting carbanion acts as a Michael donor in the propagation step and attacks the second vinylic monomer, which acts as a Michael acceptor. Consequently, a dimer is formed that acts as a new carbanion. The propagation step repeats itself, thereby enabling the polymer chain to extend. The polymer chain continues to grow until a weak acid or an electrophile is added to terminate the polymerization process. Interestingly, in the absence of any terminating agents, the propagating chain’s end acts as a stabilized carbanion site, and the polymerization process continues uniformly as long as the monomers are available. Therefore, anionic polymers are often referred to as living polymers.

Tags
Anionic Chain growth PolymerizationMechanismInitiationPropagationTerminationNucleophilic AnionButyl LithiumCarbanionElectron withdrawing GroupMichael DonorMichael AcceptorDimer FormationPolymer Chain GrowthTerminating AgentsLiving Polymers

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21.12 : Anionic Chain-Growth Polymerization: Mechanism

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21.1 : Characteristics and Nomenclature of Homopolymers

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21.2 : Characteristics and Nomenclature of Copolymers

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21.3 : Polymers: Defining Molecular Weight

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21.4 : Polymers: Molecular Weight Distribution

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21.5 : Polymer Classification: Architecture

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21.6 : Polymer Classification: Crystallinity

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21.7 : Polymer Classification: Stereospecificity

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21.8 : Radical Chain-Growth Polymerization: Overview

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21.9 : Radical Chain-Growth Polymerization: Mechanism

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21.10 : Radical Chain-Growth Polymerization: Chain Branching

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21.11 : Anionic Chain-Growth Polymerization: Overview

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21.13 : Cationic Chain-Growth Polymerization: Mechanism

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21.14 : Ziegler–Natta Chain-Growth Polymerization: Overview

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21.15 : Step-Growth Polymerization: Overview

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