Sustainability and efforts to curb the impending climate crisis must aim to do more than reduce carbon emissions. Creating eco-friendly materials and manufacturing processes that avoid using toxic chemicals or harmful extraction from the environment is an important step in minimizing our society’s deleterious effects on the planet.
A team of researchers from Vienna University of Technology and Imperial College London, led by Professor Miriam Unterlass, have developed a new, non-toxic synthetic method to create eco-friendly, high-performance organic materials.
“[Organic high-performance materials show] outstanding properties, such as high resistance against aggressive chemicals and mechanical stress, which makes them suitable for a multitude of extremely demanding applications, e.g., in the aeronautics, aerospace, automotive, or sports equipment industry,” said Unterlass. “Compared to other highly stable materials, such as metals and ceramics, their low densities enable a broad range of lightweight applications in various fields (for example, saving weight is extremely important for constructing airplanes). And the fact that they are organic comes along with being built up exclusively of very abundant elements.”
To date, this class of materials can only be produced using synthetic strategies that use harmful processing chemicals. “Many of the solvents and catalysts employed [during their synthesis] are problematic for the environment and our health,” added Unterlass. “Some are even known to be carcinogenic. With our research we are aiming towards overcoming these issues.”
The team’s breakthrough innovation circumvents current toxic synthetic strategies by simply using hot water and high pressure. In their recent study published in Angewandte Chemie, the researchers were able to demonstrate the production of two important classes of polymers using their hydrothermal reaction, which takes place in closed pressure vessels — similar to conventional pressure cookers — called autoclaves.
Under regular conditions, the condensation reactions demonstrated in the paper would be impossible, but according to Unterlass, “Under these high-pressure and high-temperature conditions, the properties of water change drastically.”
The study’s findings suggest that high-temperature water generated under such high temperatures and pressures facilitates the chemical transformation by improving dissolution of organic compounds in water, lowering the necessary temperature of reaction, and possibly facilitating the dehydration process.
The current study builds off previous work in which Unterlass and her team were able to synthesize polyimides, which are plastics used extensively in the aviation and electronics industries. The team has extended their protocol to produce polybenzimidazoles and pyrrone polymers.
Polybenzimidazoles are one of the most widely used fibers for various protective, fire-proof clothing used in firefighters’ and astronauts’ suits, and are also commonly used as membranes in fuel cells. Pyrrone polymers, on the other hand, have interesting electronic properties and the potential to be used in constructing efficient battery electrodes.
“We hope that we can inspire more researchers to employ hydrothermal processes for generating various types of organic materials,” said Unterlass. “The technique is simple and easy-to-use and avoids toxic solvents. Moreover, hydrothermal syntheses often generate superior crystallinity, which is beneficial for many materials’ properties. I am truly convinced that there is a lot to explore and that a plethora of intriguing and novel materials can be generated by taking advantage of the sheer power of hot water.”
Reference: M. J. Taublaender, et al. ‘Hydrothermal Generation of Conjugated Polymers on the Example of Pyrrone Polymers and Polybenzimidazoles.’ Angewandte Chemie International Edition (2020). DOI: 10.1002/anie.202000367