Unlocking smart polymer composite potential
Kailong Jin (center), an assistant professor of chemical engineering in the School for Engineering of Matter, Transport and Energy, part of the Ira A. Fulton Schools of Engineering at Arizona State University, is exploring the fundamental nature of dynamic polymer networks, along with support from chemical engineering doctoral candidate Mengdi Chen (background). Photographer: Erika Gronek/ASU
Self-healing materials, like the shapeshifting robots in “Terminator 2: Judgement Day,” are transcending the realm of science fiction with help from Kailong Jin. Jin is an assistant professor of chemical engineering in the School for Engineering of Matter, Transport and Energy, part of the Ira A. Fulton Schools of Engineering at Arizona State University.
His research in vitrimers — a type of resilient plastic molecule that changes its shape and repairs itself — explores the rare bonding properties that give vitrimers their adaptability. By incorporating vitrimers into common manufacturing materials, researchers can incorporate desirable traits from plastics.
All polymeric molecules in a material are connected by tiny chemical bonds. Vitrimers have bonds that can break and re-form when the material is heated or stressed. They have a dynamic and infinite bonding network that can process stress through chemical bond exchanges, ultimately healing and reshaping themselves.
Jin’s proposal has earned him the 2025 Air Force Office of Scientific Research Young Investigator Program award, which supports young career scientists and engineers who demonstrate exceptional ability and promise.
From airplane parts that last longer to car bumpers that can take a hit and recover, there are countless applications for vitrimers down the line.
Cracking the code of polymer stress
The next step in cracking the vitrimer knowledge gap is to understand how and why vitrimers regulate their dynamic bonding network.
Jin and his team have incorporated silica nanoparticles into vitrimers to develop vitrimer composites. When heat or force is applied to a composite, it typically concentrates at the point of contact between the filler silica nanoparticles and the polymer matrix, triggering a reorganization of the chemical bonds that distributes the force among the molecules’ bonding network.
Since vitrimers form endless networks of dynamic bonds, their polymers not only respond to the original stress but also to the reactions of neighboring polymers. This creates a more active and dynamic exchange of bonds throughout the material.
“A fundamental knowledge gap in this field is the lack of understanding of the vitrimer interphase regions and how these interfaces alter local bond exchange energy transfer,” Jin says. “This project’s overarching objective is to understand how heat and motion affect the form, function and bond exchanges within vitrimer composites.”
Jin plans to use a fluorescent probe to obtain location-specific fluorescence signals that can map out stress to help understand how the vitrimer engages with and distributes stress through dynamic bond exchange reactions.
“This research will elucidate how near-interface dynamics and kinetics on the nanoscale contribute to the macroscopic performance of vitrimer composites,” he says. “The fluorescence’s contact-free nature will allow one to monitor vitrimer composites’ stress relaxation in situ, during dynamic mechanical testing to obtain information directly relatable to their performance in real-world applications.”
Shaping the future of smart composite materials
Understanding how vitrimers process stress at the microscopic scale could pave the way for engineers to design products that are tougher, longer-lasting and better for the environment.
Jin is eager to fill the fundamental knowledge gaps in the behaviors of vitrimer composites and explore the desirable properties for manufacturing durable materials.
“Vitrimer composites have the potential for damage tolerance, adaptive shapes, lower maintenance costs, multifunctional integration, reduced environmental footprint and even self-healing,” Jin says.
Anthony Waas, the director of the School for Engineering of Matter, Transport and Energy, says he is excited for Jin to uncover the fundamental traits of vitrimers.
“That his project was picked out of so many proposals is impressive and confirms the potential impact of his research,” Waas says. “I look forward to the advancement he’ll make in the next few years.”
