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Arthur T Knackerbracket has found the following story:

In an unexpected finding, chemist Sankaran "Thai" Thayumanavan and colleagues at the University of Massachusetts Amherst show for the first time how movement of a single chemical bond can compromise a membrane made up of more than 500 chemical bonds. Their system uses light as a switch to create a reversible, on-demand molecular control mechanism.

Thayumanavan explains, "There are many applications that one can imagine developing from these fundamental findings, especially ones that need controlled release. For example, we have shown that two compounds that would readily react with each other can be in the same solution but are separated by a very thin membrane made of a few nanometers and therefore do not react with each other."

"But upon exposure to light, the membrane gets compromised to allow the two components to react with each other," he adds. "The interesting thing is that the membrane is not permanently compromised upon exposure to light, but only when the light is on."

His postdoctoral associate Mijanur Rahaman Molla and doctoral student Poornima Rangadurai conducted most of the experimental work. The UMass Amherst group also collaborated with theoretical chemists Lucas Antony and Juan de Pablo at the University of Chicago, who modeled the system in order to more deeply understand it, Thayumanavan notes. Details are online now in Nature Chemistry.

Such reversible molecular controls that respond only when there is a source of energy are quite rare in artificial systems, he says. Usually in artificial, human-made systems, "materials are in an equilibrium state, so if you have a particle that responds to pH change and you put it into an environment that triggers a change, it stays changed. You can't put the genie back into the bottle."

Mijanur Rahaman Molla, Poornima Rangadurai, Lucas Antony, Subramani Swaminathan, Juan J. de Pablo, S. Thayumanavan. Dynamic actuation of glassy polymersomes through isomerization of a single azobenzene unit at the block copolymer interface. Nature Chemistry, 2018; DOI: 10.1038/s41557-018-0027-6

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