Understanding the properties of something chaotic such as a bowl of spaghetti may seem a daunting task. But that’s what Garry Rumbles from the National Renewable Energy Laboratory in the USA, Natalie Stingelin from Imperial College London in the UK, and coworkers are trying to do. With success. They study polymers – long spaghetti-like molecules made of repeating atomic subunits – and have now uncovered how the microstructure of these polymers controls the behaviour of optically generated electrical charges in such a tangled molecular web, with important implications for the design of electronic devices.
The physical properties of polymers depend a lot on the length of the molecules as a whole, the atomic make-up of their structural units and the physical interactions between the individual strings. That’s why polymers come in so many forms, from hard plastics to stretchable synthetic rubbers. And what Stingelin and Rumbles now show is that also their electronic properties depend not only the chemical make-up of the polymers, but also the details of their structure and their molecular weight. This has dramatic consequences for the search of new polymers for various optical and electronic applications, says Stingelin. “Are there otherwise wonderful polymers out there that were cast aside because their creators tested the wrong molecular weight? We think it’s quite possible.”