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Related Concept Videos

Radical Reactivity: Concentration Effects01:20

Radical Reactivity: Concentration Effects

In a radical reaction, the concentration of starting materials governs the selectivity of a radical. For example, the reaction between an alkyl halide and an alkene, in the presence of tin hydride and AIBN, begins with the generation of a tin radical. The generated radical then abstracts halogen from the alkyl halide, producing an alkyl radical. This alkyl radical can either react with tin hydride, yielding an alkane, or add to an alkene, generating a nitrile-stabilized radical, eventually...
Radical Chain-Growth Polymerization: Overview01:10

Radical Chain-Growth Polymerization: Overview

Chain-growth or addition polymerization is successive addition reactions of monomers with a polymer chain. In radical chain-growth polymerization, the reaction proceeds via a free-radical intermediate. The free radical is formed from radical initiators, which spontaneously generate free radicals by homolytic fission. Organic peroxides (such as dibenzoyl peroxide, as shown in Figure 1) or azo compounds are popular radical initiators. A low concentration ratio of radical initiator to monomer is...
Radical Chain-Growth Polymerization: Mechanism01:09

Radical Chain-Growth Polymerization: Mechanism

The radical chain-growth polymerization mechanism consists of three steps: initiation, propagation, and termination of polymerization. The polymerization initiates when a free radical generated from the radical initiator adds to the unsaturated bond in the monomer. The unpaired electron of the free radical and one π electron in the unsaturated bond creates a σ bond between the free radical and the monomer. As a result, the other π electron in the unsaturated bond converts this species into the...
Radical Reactivity: Intramolecular vs Intermolecular01:33

Radical Reactivity: Intramolecular vs Intermolecular

Radical reactions can occur either intermolecularly or intramolecularly. In an intermolecular radical reaction, a nucleophilic radical adds to an electrophilic alkene or vice versa. In such reactions, the radical and generally the alkene, which is also called the radical trap, are two different molecules. Additionally, for such intermolecular reactions to occur, the radical trap must be active, present in an excess concentration, and the radical starting material must have a weak carbon–halogen...
Radical Reactivity: Steric Effects01:10

Radical Reactivity: Steric Effects

The presence of electron-donating, electron-withdrawing, or conjugating groups adjacent to a radical center, imparts electronic stabilization to the radicals. Examples of such electronically-stabilized radicals are triphenylmethyl, tetramethylpiperidine‐N‐oxide, and 2,2‐diphenyl‐1‐picrylhydrazyl. These radicals are remarkably stable and are known as persistent radicals. Some of the persistent radicals can even be isolated and purified.
Along with electronic factors, steric factors also account...
Cationic Chain-Growth Polymerization: Mechanism00:57

Cationic Chain-Growth Polymerization: Mechanism

The cationic polymerization mechanism consists of three steps: initiation, propagation, and termination. In the initiation step of the polymerization process, the π bond of a monomer gets protonated by the Lewis acid catalyst, which is formed from boron trifluoride and water. The protonation of the π bond generates a carbocation stabilized by the electron‐donating group. In the propagation step, the π bond of the second monomer acts as a nucleophile and attacks the generated carbocation,...

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Related Experiment Video

Updated: Jul 19, 2026

Atom Transfer Radical Polymerization of Functionalized Vinyl Monomers Using Perylene as a Visible Light Photocatalyst
06:49

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Published on: April 22, 2016

Diminishing catalyst concentration in atom transfer radical polymerization with reducing agents.

Krzysztof Matyjaszewski1, Wojciech Jakubowski, Ke Min

  • 1Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, PA 15213, USA. km3b@andrew.cmu.edu

Proceedings of the National Academy of Sciences of the United States of America
|October 13, 2006
PubMed
Summary

New methods for atom transfer radical polymerization (ATRP) use initiators for continuous activator regeneration (ICAR) and activators regenerated by electron transfer (ARGET) to control polymer synthesis with very low catalyst concentrations.

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Area of Science:

  • Polymer Chemistry
  • Organic Synthesis
  • Catalysis

Background:

  • Atom Transfer Radical Polymerization (ATRP) traditionally requires higher catalyst concentrations.
  • Low catalyst concentrations lead to activator deactivation via termination reactions.
  • Efficient regeneration of the activator is crucial for controlled polymerization at low catalyst loadings.

Purpose of the Study:

  • Introduce and evaluate Initiators for Continuous Activator Regeneration (ICAR) and Activators Regenerated by Electron Transfer (ARGET) ATRP.
  • Enable controlled polymer synthesis using significantly reduced catalyst concentrations.
  • Investigate the role of ligands and reducing agents in optimizing these ATRP techniques.

Main Methods:

  • Utilized ICAR with organic free radical initiators to regenerate the Cu(I) activator.
  • Employed ARGET ATRP with organic reducing agents (hydrazine and phenol derivatives) for Cu(I) regeneration.
  • Synthesized polystyrene, poly(methyl methacrylate), and acrylates with low polydispersity (Mw/Mn < 1.2).
  • Studied copper complexing ligands such as Me6TREN and TPMA.
  • Performed mechanistic studies and kinetic modeling for system optimization.

Main Results:

  • Achieved controlled polymerization of polystyrene and poly(methyl methacrylate) with 10-50 ppm catalyst using ICAR.
  • Realized controlled synthesis of acrylates with catalyst concentrations as low as 50 ppm using ARGET.
  • Identified optimal ligands and reducing agents by analyzing side reactions like complex dissociation and reducing agent complexation.
  • Demonstrated the effectiveness of both techniques in homo- and block (co)polymerizations.

Conclusions:

  • ICAR and ARGET ATRP enable controlled polymer synthesis at unprecedentedly low catalyst concentrations.
  • Careful selection of ligands and reducing agents is vital for minimizing side reactions and maximizing efficiency.
  • These advanced ATRP methods offer practical advantages for polymer synthesis where catalyst removal is undesirable.