'Molecular flask' created for polymer chemistry

Living systems, like cells, can carry out chemical reactions in very small spaces, sometimes involving single molecules. For many years, researchers have attempted to emulate this to allow for the manufacturing of specialised chemical compounds, but with limited success. Now, a new tool has been developed that assists with controlling chemical reactions.

Researchers based at the Institute of Industrial Science, The University of Tokyo, have created a ‘molecular flask’ — which modulates the reactivity of the reactions happening in its interior — using a carefully constructed single polymer molecule with a unique shape. Described in the Journal of the American Chemical Society, their tool could allow important polymers — large, chainlike molecules with many modern applications — to be created in incredibly small spaces with a high level of precision.

“Previous work in this field has created small molecular reactors based on various porous materials,” said Xiangyuan Guo, lead author on the study. “However, it is difficult to use these processes to make specific polymers, because the polymerisation reaction is not easily controlled.”

This new work created polymers based on central, wormlike molecules with many protruding side chains, known as a ‘bottlebrush’ shape. The side chains act to produce a kind of internal buffer zone that allows some substances to enter the space around the body of the polymer molecule, while keeping others out.

This zone can be as small as a single molecule and can be tailored to provide adequate space for the formation of other polymers. Inside these nanosized pockets, chemicals can react to produce only certain desired products, protected from the effects of their surroundings. For this reason, materials that are otherwise difficult to synthesise can be obtained using this system.

“One of the main advantages of this new process is that it is extremely versatile,” said senior author Shintaro Nakagawa. “This was demonstrated by synthesising two completely different types of polymers, including a specialised conjugated polymer based on thiophene with applications in optoelectronics.”

The spaces inside these carefully designed bottlebrush polymers are extremely small: on the order of tens of nanometres, meaning billionths of a metre. Similar to biological systems such as enzymes, these molecular-scale flasks allow an extreme level of control of chemical reactions.

In addition to making specialty polymers with many different applications, this breakthrough technology could someday be employed to produce nanoparticles and other materials with applications in medicine, sensing technology and other fields.