A Chemical Festival of Light for Modern Polymers

Light has long captivated Katharina Ehrmann, a 33-year-old chemist. During her postdoctoral research at the Queensland University of Technology in Brisbane, Australia, from 2021 to 2022, she explored light-based chemistry. Reflecting on her time there, she recalls the joy of strolling home through a botanical garden illuminated by lights after an exhausting day in the lab.

Ehrmann's current research focuses on light-based 3D printing, a method where a liquid medium is layered and cured with a laser to create solid plastic structures. However, she notes that the materials produced often have limited applications, being either robust and rigid or soft and flexible. To address this limitation, she has approached her work with an innovative perspective, harnessing the potential of 3D printing for the synthesis of diverse chemical materials.

Her inquiry revolves around whether a single polymer can exhibit multiple properties simultaneously, specifically if it can be both semi-crystalline (partially crystalline) and amorphous (non-crystalline). Semi-crystalline plastics are typically hard and opaque, while non-crystalline types are flexible and transparent. The existence of both characteristics in a single polymer leads to the development of composite materials, which have practical applications in fields such as soft robotics and medical technology, particularly in prosthetics.

Until recently, achieving both traits in a single manufacturing process was not feasible. However, Ehrmann and her team at the Institute for Applied Synthesis Chemistry at TU Wien have demonstrated for the first time that semi-crystalline and crystalline phases can coexist within a single material. This significant breakthrough earned her the Dr. Ernst Fehrer Award for outstanding research achievements at the end of 2024.

Ehrmann likens her 3D printing technique to that of a reactor, emphasizing that the more parameters she can adjust, the more varied the resulting materials can be. Key parameters in her methodology include light intensity and temperature--factors that had seen little variation in traditional 3D printing methods. In their laboratory experiments, her team prints at temperatures ranging from room temperature to 140 degrees Celsius while simultaneously altering light intensity and color to control the reactions involved.

Initially, the goal of her dissertation project was to create a semi-crystalline material. The team began with a liquid medium known to be crystalline and subjected it to light exposure. Surprisingly, the results exceeded expectations, yielding both semi-crystalline and amorphous phases within the material.

The underlying theory posits that during the polymerization process, the temperature rises due to an exothermic reaction, releasing energy. Since the crystallinity in the liquid phase is temperature-dependent, the team found themselves at the boundary of isotropy--a chemically disordered and amorphous state. This led to the hypothesis that the chemical process could be regulated not only by temperature but also by light.

When not contemplating the crystallinity of polymers, Ehrmann enjoys swimming in the Alte Donau in Vienna and looks forward to the upcoming summer light festival there.

About Katharina Ehrmann: A native of Innsbruck, she studied chemistry at the University of Innsbruck and the University of Edinburgh. She completed her doctorate in polymer chemistry at TU Wien by 2020 and conducted research at the Queensland University of Technology in Australia from 2021 to 2022. Currently, she leads the Additive Manufacturing team at TU Wien.