A scientist with IBM has discovered the first of a new class of polymers, a self-healing material that has other valuable properties. The new material is part of a new class of polymers, the first discovered in over 20 years. These new polymers could be used in electronics, or in components of ground and air vehicles.
Self-repairing is the most unusual property of this new class of polymers. When pieces are cut apart then placed close enough to each other molecular bonds are formed in a few seconds. Hydrogen bonding drives the repair process. This new polymer is highly resistant to solvents and physical stress. The self-healing can be reversed using ordinary water, which sounds like a serious problem. However, the new polymers could be used in temporary adhesives, which are sometimes used in medicine.
In addition to repairing itself and being resistant to solvents, the polymer can be disassembled by acid, which makes it easily recyclable. Recycling electronic parts could become faster, cheaper and more environmentally friendly. Defective parts with the polymers could be easily disassembled and re-formed correctly. The polymers used in such applications now are thermosets, meaning they cure irreversibly when exposed to heat.
Jeannette “Jamie” Garcia, a chemist at an IBM-managed laboratory, discovered this unusual new material. Garcia was experimenting with three chemicals, but forgot to add one of the chemicals before leaving the beaker alone for a time. The two chemicals in the beaker formed a solid white block in the beaker. A team led by chemist James Hedrick conducted tests on the material.
According to a statement on IBM’s Web site, the polymers can be transformed into new structures that are 50 percent stronger. Such a material, IBM notes, could have impacts in every industry trying to innovate in the areas of engineering and product design. Discovery of this new family of polymers was described in the journal Science on May 16.
Polymers are chains of molecules that are chemically bonded together. They have been used in almost all technology developed since the Industrial Revolution began. In particular, all modern electronic devices use polymers in their cases if not for internal components. Polymers are ubiquitous in modern society. For example, they are found in clothing fibers, fast-food containers and many aircraft and automotive parts.
While the original accident seemed to produce one new polymer, there were actually two new classes of materials. Both materials have important qualities, like high stiffness, solvent resistance and self-healing ability. The new materials could also be made into resins and mixed with other materials.
The newly discovered polymer does have one weakness: heat. At up to 350 degrees Celsius, Garcia’s polymer performs well enough, comparable to existing thermosets. Above that temperature the material starts to break down, which is a potentially fatal flaw in building circuit boards. The layer that connects chips in an integrated circuit can heat up to 425 degrees Celsius.
he IBM team that analyzed Garcia’s discovery worked backwards, using mathematical modeling, to figure out how the compound had formed. With that information, more of the material could be made and tested.
The IBM scientist’s discovery of a self-healing class of polymers opens up many new possibilities, for recycling as well as manufacturing. The ability to easily recycle things like laptop cases and smart phones would divert thousands of tons of waste from landfills or incinerators each year.
By Chester Davis