A new class of self-healing polymer hybrid materials

“Self-healing” materials have the potential to enable longer-lasting, more durable products and devices. The specially designed substances can automatically repair damage to themselves, either completely or partially, without human intervention, similar to how human skin heals a cut.   

Researchers at Carnegie Mellon University have created a new class of polymer hybrid material featuring “integrated self-healing”. By admixing a flexible, linear copolymer with rigid brush particles, the team, led by professors Michael Bockstaller and Krzysztof Matyjaszewski, demonstrated mechanically strong hybrid materials in which two mechanisms, dubbed ‘intrinsic’ and ‘extrinsic’ self-healing, work together to facilitate structural recovery after damage. 

“This approach enables the fabrication of high modulus, or stiffer, self-healing polymers by derivatizing a chemistry that is already in widespread use, rather than developing an entirely new chemistry for which no applications yet exist,” said Bockstaller. “We hope that such a benefit could accelerate the adoption of this approach.”

Using transmission electron microscopy (TEM) tools in the Materials Characterization Facility, Hanshu Wu and Yuqi Zhao, two graduate students who equally contributed to this work, observed the formation of a hierarchical microstructure in which the flexible polymer additive concentrates within channel-like spaces between brush particles. This created a capillary network structure similar to biological systems, that allows for transport of the flexible polymer.  

Polymers are often used in applications in concert with other materials or material systems, and in these applications device failure is often linked to the breakdown of the polymer component. In such use scenarios, polymers have a critical performance limiting role. By combining precision polymer chemistry, such as atom-transfer radical polymerization, with bio-inspired methods of self-assembly, this innovative approach demonstrates a scalable way to produce multifunctional materials that do not lose their special properties, even after being damaged multiple times. 

 

We believe that we have just been scratching the surface of performance enhancements that might be possible using this approach

Michael Bockstaller, Alcoa Professor, Department of Materials Science and Engineering

The combination of mechanical strength and self-healing in  this newly developed material is especially promising for the design of long-lasting, high-performance polymers that could be used in a variety of applications such as coatings, electronics, and packaging. 

“We believe that we have just been scratching the surface of performance enhancements that might be possible using this approach,” notes Bockstaller.  

Future research will focus on expanding the range of materials to which the approach can be applied, to further increase the modulus of self healing materials, and to explore strategies that enable the acceleration of self-healing processes.