Chuck Bednar for redOrbit.com – Your Universe Online
In a world that faces a steady stream of terror threats from the likes of Al Qaeda, ISIS/ISIL and other radical extremists, the possibility of an attack that utilizes an undetectable chemical warfare agent has been a grave concern – until now.
Writing in the journal ACS Macro Letters, MIT chemists Timothy M. Swager and Jonathan G. Weis revealed they are developing thin-film materials that quickly change colors after coming in contact with chemical agents, potentially saving thousands of lives.
While there are other methods that can be used to detect chemical weapons, most of them are based on liquids, which are less practical to use than thin films, the study authors said. Their new material is better for real-time detection because it is easier to use and works continuously.
The researchers synthesized dithienobenzotropone-based conjugated alternating copolymers through a process known as direct arylation polycondensation. Next, they used hydride reduction modification procedures to create “cross-conjugated, reactive hydroxyl-containing copolymers that undergo phosphorylation and ionization” when exposed to a simulated agent.
Colorimetric sensors work well because they are simple, portable, and able to integrate functionality and react with the agents, the study authors noted. Few thin film colorimetric sensors exist, even though film allows for the real-time detection of organophosphates.
Organophosphates, the researchers explained, are the basis of many types of chemical warfare agents. The chemicals are toxic because they inhibit acetylcholinesterase (AChE) by phosphorylating the active site of the enzyme. In order to be effective in detecting chemical attacks, a method must be simple to operate, sensitive to the agents, portable, and cost-effective.
Most previous approaches to using chemical-detecting colorimetric films centered around embedding small chromogenic molecules into a polymer matrix, they added. However, by attaching or directly incorporating chromophores into polymers, the films can become more robust and enable stimuli-responsive materials that undergo changes in response to such agents.
Ultimately, the MIT chemists said that they successfully synthesized “a cross-conjugated polymer that undergoes rapid phosphorylation and ionization to form an aromatic, conjugated polymer upon exposure” to chemical warfare agent mimic diethylchlorophosphate (DCP). Furthermore, their method worked both in solution and as a thin film.
“The resulting cationic copolymer is highly colored and enables colorimetric and spectroscopic detection” of a simulated nerve agent, Swager and Weis added. “With the inclusion of a reactive moiety into the polymer backbone, we envision a class of stimuli-responsive materials that not only detect the presence of chemical threats, but also functionally respond by undergoing conformational changes that affect their physical properties.”
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