Small-molecule organic eutectics could replace plastics

Plastics have long been a staple of modern manufacturing, but their environmental impact has increased the demand for eco-friendly alternatives. Researchers at the University of Warwick have made significant progress in finding sustainable alternatives to conventional plastics.

In response to growing environmental concerns, the move toward a circular economy, and changing consumer preferences, the research team identified that certain mixtures of small organic molecules—materials created by mixing crystalline components—form interesting glasses and viscous liquids. These organic eutectics are promising candidates to replace polymers in various products.

The team successfully developed a series of hydrophobic eutectic liquids and molecular glasses, each carefully crafted by combining different crystalline components. Using advanced techniques such as differential scanning calorimetry (DSC) and UV-vis spectroscopy, the eutectic compositions were precisely determined. The analysis was refined using a trained partial least squares regression model, ensuring accuracy in identifying optimal material blends.

One of the key challenges in creating sustainable alternatives to plastic is ensuring long-term stability. The Warwick team addressed this by testing the amorphous materials over an extended period of up to 14 months, using powder X-ray diffraction (PXRD) to confirm their resistance to crystallization. This durability is essential to ensure the products maintain their integrity throughout their shelf life.

In addition to stability, the researchers investigated the processability of these materials by examining their rheological properties. They found that all of the liquids exhibited low brittleness indices, making them suitable for various manufacturing processes, including glass blowing, fiber drawing, film forming, and molding.

Importantly, the team demonstrated that the properties of these materials could be tailored to specific applications by mixing different eutectic systems or incorporating plasticizers.

Prof. Dr. ir. Stefan Bon, principal investigator of the study, now published in Chemical sciencessays: “The initial plan was to develop a conceptual material that was anything but plastic for the formulation industry.

“Dr. Joshua Ryan, a talented former PhD researcher in my team, BonLab, undertook a systematic study of mixing small hydrophobic organic molecules that could undergo a variety of non-covalent interactions with each other. The fact that these hydrophobic eutectic systems had such remarkable physical properties was beyond our initial expectations.

“We called on our colleague, Professor Gabriele Sosso, to study, through computer simulation, how these eutectic mixtures interact at the molecular level. These small molecule organic eutectic systems offer the possibility of further developing high-performance materials that can replace conventional polymers in various applications.

“In some ways, they can be considered a noncovalent analogue of dynamic reversible macromolecular covalent materials, known as vitrimers.”

To demonstrate the practical potential of these materials, the researchers conducted a controlled release study using a eutectic system composed of 4-hydroxychalcone and bifonazole as a matrix. This study serves as a proof of concept, highlighting the versatility of eutectic materials in applications such as drug delivery and beyond.