Volume 94 Issue 43 | p. 8 | Concentrates
Issue Date: October 31, 2016

Mechanical force stimulates polymer growth

Ultrasound activates catalyst for atom-transfer radical polymerization
Department: Science & Technology
News Channels: Materials SCENE, Organic SCENE
Keywords: materials, Aaron Esser-Kahn, polymer, mechanochemistry, atom-transfer radical polymerization, piezochemistry

To date, most examples of polymer mechanochemistry—in which mechanical force initiates a chemical reaction—have involved breaking covalent bonds. But chemists working in this field would also like to use mechanical force to build bonds, just as the body uses mechanical force to restructure and reinforce bone. Taking a step in this direction, chemists at the University of California, Irvine, have developed a mechanically controlled radical polymerization process (Nat. Chem. 2016, DOI: 10.1038/nchem.2633). Aaron P. Esser-Kahn, Hemakesh Mohapatra, and Maya Kleiman used ultrasound to agitate piezoelectric BaTiO3 nanoparticles, generating a potential that then reduced a copper(II) complex. The reduced copper(I) complex then reacted with an atom-transfer radical polymerization initiator, ethyl α-bromoisobutyrate, to stimulate polymerization of n-butyl acrylate monomer. The longer the team used ultrasound, the longer the polymer chains grew. Now the chemists are gearing up to use environmental vibrations to spur polymerization reactions.

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Ultrasound initiates this polymerization reaction.
Reaction scheme shows conversion of linear peptides into cyclic peptidomimetics, each containing an oxadiazole ring and a tertiary amine.
 
Ultrasound initiates this polymerization reaction.
 
Chemical & Engineering News
ISSN 0009-2347
Copyright © American Chemical Society

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