Researchers from the P3R team at Softmat have developed new vitrimers by developing heat-activated radical chemistry. This novel approach gives these materials, which are resistant, repairable and recyclable when heated, the ability to be reshaped without any loss of performance. A major breakthrough in the design of sustainable and recyclable polymers! These results are published in the journal Angew. Chem. Int. Ed.
Thermosetting plastics play an essential role in high-tech sectors (aeronautics, automotive, electronics) due to their high-performance properties, such as exceptional resistance to heat and chemicals. But this robustness has a downside: once moulded and cured, they cannot be remelted or recycled. Over the past decade, new materials called vitrimers have revolutionised this paradigm. These materials retain a network similar to thermosets, but their chemical bonds can be reorganised under the effect of heat, giving them unprecedented malleability without any loss of performance.
Until now, the design of the vast majority of vitrimers has been based on conventional chemical function exchange mechanisms. Scientists are proposing an innovative approach by exploiting a radical reaction, i.e. one involving an atom or molecule with a single unpaired electron, which is extremely reactive. These radicals then initiate dynamic associative exchanges between polymer chains, rather like bricks in a wall that can detach and reattach elsewhere while maintaining the solidity of the whole. While radicals are typically generated irreversibly via light or the use of initiators, these scientists generated them for the first time under the effect of heat and in a completely reversible manner from a molecule containing two sulphur atoms (disulphide bonds).
In addition, they showed that a very small amount of disulphide (2%) was sufficient to make the material reconfigurable. Marc Guerre, who is leading this research, explains: “It can be reshaped at 200°C in just a few minutes, without any loss of rigidity or change in its structure. And even after 3 reshaping cycles, its mechanical and thermal properties remain unchanged!”
This strategy paves the way for a new generation of polymers combining the thermal stability of thermosets with the recyclability of thermoplastics. Beyond recycling, this thermally activated radical chemistry could also inspire the design of smart materials capable of self-repairing, reconfiguring, or adapting to their environment. This breakthrough enriches the vitrimer landscape and offers new prospects for the transition to a circular and sustainable polymer industry.
Read Marc’s interview in Angew. Chem. Int. Ed.
Image capture: reshaping of the vitrimer after hot compression at 170°C © Marc Guerre & Alexis Millan / Softmat