New cat on the block: NMR clues

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  • Published: Oct 15, 2018
  • Author: David Bradley
  • Channels: NMR Knowledge Base
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Electrifying polymers

Polymers synthesized using electropolymerization are attracting attention once again in the world of catalytic research. One of the first pairings of nuclear magnetic resonance (NMR) spectroscopy and electrochemical tests reveals the details. Crop of NMR detail from AIP Adv

Polymers synthesized using electropolymerization are attracting attention once again in the world of catalytic research. One of the first pairings of nuclear magnetic resonance (NMR) spectroscopy and electrochemical tests reveals the details.

Ye Feng, Chengsen Zhao, Shuo-Hui Cao, Shuhui Cai, Huijun Sun, and Zhong Chen provide the first detailed characterization of the electrochemical properties of polyaniline and polyaspartic acid (PASP) thin films. Writing in the journal AIP Advances, the team explains how they used a wide range of tests to characterize the polymers, especially their capacity for catalyzing the oxidation of popularly used materials, hydroquinone and catechol. The paper marks one of the first times standard electrochemical tests have been combined NMR in this context.

"Because these materials can be easily prepared in an electric field and are cost-effective and environmentally friendly, we think they have the potential to be widely used," explains team member Shuo-Hui Cao.

Electrocatalytic response

PASP has previously been shown to have excellent electrocatalytic responses to biological molecules, but it might also have utility because of its ability to lower the oxidational potential in oxidation-reduction reactions. Reducing the oxidation potential is key for finding further uses for two materials used extensively as raw materials and synthetic intermediates in pharmaceuticals, hydroquinone and catechol.

Moreover, as Cao and his colleagues exlplain, conductive polymers, such as polyaniline, have attracted attention for their high conductivity and low cost. Their tests on its ability to alter hydroquinone and catechol used several standard electrochemical techniques, including attenuated total reflection Fournier transform infrared spectrophotometry, cyclic voltammetry, and electrochemical impedance spectroscopy. However, the addition of proton NMR spectroscopy allowed them to monitor the progress of each reaction by directly measuring how quickly reactants were used and products were created. Cao said that their work using NMR analysis on catechol looks to fill a gap they found in the literature. "The NMR technique allows us to find out more about their molecular structure and better compare the catalysts' characteristics quantitatively," he explains.

Polymer mods

The group discovered that the polymer-modified electrodes both improved conductivity. PASP's catalytic activity of hydroquinone and catechol was found to outpace that of polyaniline by a factor of two. Subsequent NMR studies confirmed that electrically induced molecular transformations allowed PASP to serve as a better catalyst. The findings led the researchers to postulate that polyaspartic acid electropolymerized thin films might be more suitable for use as catalysts over polyaniline in many situations.

The team now hopes that they can develop the application of NMR spectroscopy still further rin this area. The use of two-dimensional techniques could extend the work to still more complicated materials.

Related Links

AIP Adv 2018, online: "The electrochemical oxidation of hydroquinone and catechol through polyaniline and poly(aspartic acid) thin films: A comparative study"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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