A new generation of dynamic materials gets the green light

via Queensland University of Technology

Developing synthetic materials that are as dynamic as those found in nature, with reversibly changing properties and which could be used in manufacturing, recycling and other applications, is a strong focus for scientists.

In a world-first, researchers from QUT, Belgium’s Ghent University (UGent) and Germany’s Karlsruhe Institute of Technology (KIT) have pioneered a novel, dynamic, reprogrammable material – by using green LED light and, remarkably, darkness as the switches to change the material’s polymer structure, and using only two inexpensive chemical compounds. One of these compounds, naphthalene, is well known as an ingredient in moth repellents.

The new dynamic material could potentially be used as a 3D printing ink to print temporary, easy-to-remove support scaffolds. This would overcome one of the current limitations of the 3D process to print free-hanging structures.

The research is part of an ongoing international collaboration between QUT macromolecular chemist and Australian Research Council Laureate Fellow Professor Christopher Barner-Kowollik, Dr Hannes Houck, who recently completed his PhD across QUT, UGent and KIT, UGent Professor Filip Du Prez, and KIT’s Dr Eva Blasco.

Their findings have been published in the Journal of the American Chemical Society (JACS).

Key points:

• The new material was formed with naphthalenes and the coupling molecules triazolinediones (TADs)
• As long as green LED light shone on the material it remained stable and strong
• Once the light was off and the material was kept in darkness, the chemical bonds of the network structure broke up and the material became soft and liquefied
• The hard-to-soft process could be repeated with the flick of the switch, and the light could be dimmed to modulate the mechanical  properties of the material
• Follow on research is looking at other chemical combinations that can achieve the same result

Professor Barner-Kowollik, from QUT’s Science and Engineering Faculty, said what makes the discovery unique is that light is used as the trigger to stabilise, rather than destroy, chemical bonds – so the researchers have coined a new term, light-stabilised dynamic materials (LSDMs).

“We are hoping to introduce LSDMs as a whole new class of materials,” said Dr Houck. “We debated whether to patent the new material, but decided not to wait and to publish the findings to advance knowledge and understanding of the processes involved.”

The researchers said what they have achieved is the opposite of what is usually done in chemistry and “many people didn’t think it could be done”.