New polymer gel that enables complex materials to regenerate themselves

Researchers are studying the possibility of materials that could be programmed to regenerate-themselves, replenishing the damaged or missing components, and thereby extend their lifetime and reduce cost of repairs. Researchers at the University of Pittsburgh Swanson School of Engineering, who have developed computational models to design a new polymer gel that would enable complex materials to regenerate themselves. The article was published in the American Chemical Society journal Nano Letters. The research team was inspired by biological processes in species such as amphibians, which can regenerate severed limbs. This type of tissue regeneration is guided by three critical instruction sets – initiation, propagation, and termination – which the principal investigators, Dr. Balazs describes as a "beautiful dynamic cascade" of biological events. "We needed to develop a system that first would sense the removal of material and initiate regrowth, then propagate that growth until the material reached the desired size and then, self-terminate the process." The team developed a hybrid material of nanorods embedded in a polymer gel, which is surrounded by a solution containing monomers and cross-linkers (molecules that link one polymer chain to another) in order to replicate the dynamic cascade. When part of the gel is severed, the nanorods near the cut act as sensors and migrate to the new interface. The functionalized chains or "skirts" on one end of these nanorods keeps them localized at the interface and the sites (or "initiators") along the rod's surface trigger a polymerization reaction with the monomer and cross-linkers in the outer solution. Drs. Yong and Kuksenok developed the computational models, and thereby established guidelines to control the process so that the new gel behaves and appears like the gel it replaced, and to terminate the reaction so that the material would not grow out of control. The nanorods are approximately ten nanometers in thickness, about 10,000 times smaller than the diameter of a human hair. The team also credit Krzysztof Matyjaszewski, who contributed toward the understanding of the chemistry behind the polymerization process. The next generation of research would further optimize the process to grow multiple layers, creating more complex materials with multiple functions. Principal investigator is Anna C. Balazs, PhD, the Swanson School's Distinguished Robert v. d. Luft Professor of chemical and petroleum engineering, and co-authors are Xin Yong, PhD, postdoctoral associate, who is the article's lead author; Olga Kuksenok, PhD, research associate professor; and Krzysztof Matyjaszewski, PhD, J.C. Warner University Professor of Natural Sciences, department of chemistry at Carnegie Mellon University.