A new microscopy technique developed by Maram Abadi (left), Satoshi Habuchi (right) and colleagues challenges current thinking about polymer physics. Photo: KAUST.
A new microscopy technique developed by Maram Abadi (left), Satoshi Habuchi (right) and colleagues challenges current thinking about polymer physics. Photo: KAUST.

A new technique that allows researchers to watch the motion of individual molecules within a polymer has been developed by scientists at the King Abdullah University of Science and Technology (KAUST) in Saudi Arabia. The technique, reported in a paper in Nature Communications, challenges current thinking about polymer physics and could lead to new materials that can be tailored for specific tasks.

Polymers are a large and diverse family of materials ranging from hard, rigid plastics to flexible, stretchy gels. At the microscopic level, polymers consist of long-chain molecules that are tangled together like a nanoscale plate of spaghetti. The properties of a polymer material arise from the way its component polymer chains move and interact with each other. Until now, researchers’ ability to fully understand polymer properties was hampered because it was impossible to observe the motion of individual polymer chains.

Satoshi Habuchi and his team at KAUST have now overcome this limitation using super-resolution fluorescence microscopy. “Fluorescence imaging is an excellent technique to capture real-time behavior of dynamic systems,” says Maram Abadi, a member of Habuchi’s team.

For their polymer study, Habuchi and his team created a polymer with fluorescent tags attached at several points along its long-chain molecules. Although the spatial resolution of conventional fluorescence imaging is limited to 200–300nm —insufficient for tracking the dynamics of individual polymer chains —super-resolution fluorescence imaging offers considerably sharper resolution of 10–20nm.

Super-resolution is achieved by capturing 10,000 separate fluorescence microscopy images within a few seconds, and then using a computer to combine them to generate a single super-resolution image. The technique earned its original discoverers the Nobel Prize in Chemistry in 2014.

Habuchi and his team combined this technique with a single-molecule tracking algorithm they recently developed. “It provided a powerful tool for investigating entangled polymer dynamics at the single-molecule level,” Abadi says.

The tool showed that polymer dynamics are more complex than previously thought. Up to now, polymer dynamics have been modeled using reptation theory, which considers the entire polymer chain to move as a single unit, similar to a snake. Hence the term's derivation from the word reptile. In this new study, super-resolution fluorescent microscopy has revealed that the polymer actually undergoes chain-position-dependent motion, with most motion occurring at the chain ends and the least motion occurring in the middle.

This discovery shows that polymer physics theory will have to be revised, Abadi says. “Since rheological properties of materials arise microscopically from entangled polymer dynamics, a revision of the reptation theory would have a broad impact not only on fundamental polymer physics but also on the development of a wide range of polymer nanomaterials,” she says.

The team now plans to apply its technique to more complex systems, including polymer gels and networks of biomolecules within cells.

This story is adapted from material from KAUST, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.