The new materials are characterized by high strength, resistance to solvents, the ability to self-repair cracks that appear in them, and the possibility of combining other composite materials, in order to ensure even higher strength.
Scientists at IBM's research laboratory have discovered a new type of polymers, capable of changing the world of manufacturing in the fields of transportation, aviation and microelectronics. Using a unique approach that combines extremely high-performance computing together with the chemistry of synthetic polymers, the new materials for the first time show resistance to cracks and fractures, greater strength than human bones, the possibility of restoring their original shape by themselves - and all without giving up full recycling of the original materials from which they were made . The new materials form the basis for complex polymeric structures, which add 50% to the overall structural strength, in a way that makes them particularly strong and light in weight, compared to other materials of similar strength. The research was conducted in collaboration with the universities of Berkeley in the USA, Eindhoven in the Netherlands and the King Abdulaziz City of Science and Technology (KACST) in Saudi Arabia. The results of the research are published this week, in the issue of the scientific newspaper "Science".
Polymers, a long chain of molecules linked together by chemical bonds, are an indispensable part of our daily life. They assemble a wide variety of objects - from clothes and drink bottles (polyester), paints (polycrylic), milk bottles made of plastic (polyethylene), food packaging (polyolefin, polystyrene) to central parts in vehicles and airplanes (epoxy, polyamide and polyimide). They are also an essential component of every industrial technology from the era of the industrial revolution to the present day: the steam engine, the spaceship, the computer and the cell phone.
Today's polymers are limited in certain areas. In the world of transportation and aviation, structural components are exposed to environmental hazards: from the thawing of the wing area of airplanes, through a problem with exposure to different fuels, to low resistance to stress fracture after exposure to a solvent, for example. In addition, these polymers are difficult to recycle because they cannot be melted and recast after their initial design. When exposed to high heat, they burn and emit toxic substances. As a result, the garbage sites are filled with toxic waste of various types - which endangers the environment.
new materials
The researchers at IBM have now discovered a new type of materials, which have a wide and adjustable range of strength, flexibility and weight characteristics - which present an opportunity for new applications and the development of products that rely on the unique capabilities of these materials. The new materials are characterized by high strength, resistance to solvents, the ability to self-repair cracks that appear in them, and the possibility of combining other composite materials, in order to ensure even higher strength.
The possibility to recycle these new materials is expected to have a substantial impact on the semiconductor industry, advanced manufacturing processes and the production of parts for the automotive world: from now on, it will be possible to reprocess parts and components that are found to be defective already in the production process - instead of immediately throwing them into the trash. Thus, it is possible to improve the level of output, save expenses and significantly reduce the amount of electronic waste.
In order to develop the new family of materials, the researchers at IBM used an innovative approach of "computational chemistry", which makes it possible to speed up the process of discovering the materials - in combination with experiments in the laboratory, and while relying on extremely high-performance computer systems, to build models of the chemical reactions that take place throughout the creation process the polymer.
In a future ideal world, scientists will be able to feed the computer a list of defined requirements - and task it with designing molecules that will meet exactly these requirements, as well as the production processes of these molecules. Unfortunately, new materials are still mainly discovered in laboratory experiments, relying on the knowledge, experience and scientific training of the researchers who develop them. The computational chemistry methods developed at IBM may cut a significant part of the guesswork, trial and error - and speed up a long list of development efforts. Medicines targeted at the disease, components for vehicles that will be cheap, strong and recyclable - all can be developed using computational chemistry tools.
The new polymers are created in the accepted and cheap process, which begins with a condensation reaction in which the molecules connect to each other, releasing small molecules such as water or alcohol as a byproduct. At a temperature of 250 degrees Celsius, the polymer becomes particularly strong, thanks to the reorganization of covalent bonds and the loss of liquid solvent trapped in it. The known problem is that, along with the additional strength, the polymer also becomes more fragile, similar to glass. Now, this problem has been solved, and the new polymers have even received a unique property in the form of the ability to restore fractures and cracks and self-recovery.
The new polymer is not affected by exposure to basic solutions (high pH), but selectively decomposes when exposed to particularly strong acids (low pH). Hence, under the right conditions, the polymer can be broken down into the materials from which it was built, in a way that allows the reuse of these materials in other polymers. An even stronger material can be produced, if carbon nanoparticles, or other fillers and reinforcements are mixed into the polymer, while heating to high temperatures. The process makes it possible to give polymers properties similar to those of metals - indeed, "composites" that combine polymers and reinforcing materials are used to manufacture airplanes and cars. These materials are lighter than metal - and enable savings in fuel costs.
At lower temperatures, and even at room temperature, it is possible to build a new type of polymer that behaves like an elastic gel - and is still stronger than most of the polymers known today. These new materials retain their elasticity because the solvent is trapped in the network of molecules, allowing them to stretch like a rubber band.
A very noteworthy feature of this new gel is the fact that when parts of it are cut off and then put back together, each part close to the other part, to the point of physical contact between them - the chemical bonds between the parts are renewed and make them one whole, within a few seconds. Thanks to this reproducibility, these polymers have earned the title of "self-healing". Thus, they can be thought of as a particularly suitable raw material for adhesive and dressing products, or in applications that combine them with other polymers, to build systems and components with self-recovery and self-repair capabilities. These polymers can be recycled in normal water, and can also be used in applications that require reassembly, such as transporting drugs in the body.
