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Related Concept Videos

Radical Chain-Growth Polymerization: Overview01:10

Radical Chain-Growth Polymerization: Overview

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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...
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Radical Chain-Growth Polymerization: Chain Branching01:17

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The skeletal structure of polymers synthesized via radical polymerization is always branched. For example, the polymerization of ethylene by radical polymerization results in a low-density grade of polyethylene with a heavily branched skeletal structure. Here, the radical site abstracts hydrogen from the growing chain, and the radical site shifts from the end (a primary carbon center) to anywhere within the growing chain (a secondary carbon center). Consequently, the part of the chain from the...
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Radical Chain-Growth Polymerization: Mechanism01:09

Radical Chain-Growth Polymerization: Mechanism

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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...
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Radicals: Electronic Structure and Geometry01:07

Radicals: Electronic Structure and Geometry

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This lesson delves into the geometry of a radical, which is influenced by the electronic structure of the molecule. The principle is similar to that of a lone pair, where the unpaired electron influences the geometry at the radical center.
Accordingly, the structure of a trivalent radical lies between the geometries of carbocations and carbanions. An sp2-hybridized carbocation is trigonal planar, while an sp3-hybridized carbanion is trigonal pyramidal. Here, the difference in geometry is...
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Radical Reactivity: Steric Effects01:10

Radical Reactivity: Steric Effects

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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...
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Radical Reactivity: Intramolecular vs Intermolecular01:33

Radical Reactivity: Intramolecular vs Intermolecular

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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...
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Synthesis, Cellular Delivery and In vivo Application of Dendrimer-based pH Sensors
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Polyphosphorhydrazone-Based Radical Dendrimers.

Vega Lloveras1, José Vidal-Gancedo1

  • 1Institut de Ciència de Materials de Barcelona (ICMAB-CSIC) and CIBER-BBN, Campus UAB, 08193 Bellaterra, Spain.

Molecules (Basel, Switzerland)
|March 6, 2021
PubMed
Summary

Radical dendrimers, versatile macromolecules, show promise for biomedical uses including MRI contrast agents and antioxidants. Polyphosphorhydrazone-based radical dendrimers offer metal-free applications.

Keywords:
PPH dendrimerscontrast agentsmagnetic resonance imagingorganic radicalsradical dendrimers

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Area of Science:

  • Macromolecular Chemistry
  • Materials Science
  • Biomedical Applications

Background:

  • Dendrimers are increasingly explored for novel biomedical applications.
  • Radical-based molecules, including radical dendrimers, are synthesized for diverse uses.
  • Organic radicals offer unique paramagnetic properties for advanced materials.

Purpose of the Study:

  • To review radical dendrimers based on polyphosphorhydrazone.
  • To highlight their versatility and potential in various fields.
  • To discuss the development of new metal-free contrast agents.

Main Methods:

  • Mini-review of existing literature on radical dendrimers.
  • Focus on polyphosphorhydrazone as a macromolecular platform.
  • Analysis of applications stemming from paramagnetic properties.

Main Results:

  • Polyphosphorhydrazone-based radical dendrimers are versatile macromolecules.
  • These dendrimers enable the creation of novel metal-free contrast agents.
  • Potential applications include magnetic resonance imaging, anti-tumor, and antioxidant therapies.

Conclusions:

  • Radical dendrimers, particularly polyphosphorhydrazone-based ones, are promising for biomedical fields.
  • Their metal-free nature is advantageous for contrast agents and therapeutic applications.
  • Continued research into radical dendrimers can lead to innovative devices and treatments.