A new class of ultra-strong, self-healing, recyclable polymer materials has been discovered by IBM researchers using high performance computing.
Today’s polymers materials are used in anything from food packaging to aerospace parts, but they tend to have poor stress crack resistance and are difficult to recycle because they cannot be remoulded or reworked once cured or thermally decomposed upon heating to high temperatures meaning they end up in landfill.
But now two new related classes of materials have been discovered that are resistant to cracking, stronger than bone, exhibit high stiffness and solvent resistance, and are able heal themselves once a crack is introduced giving them the potential to transform manufacturing and fabrication in the fields of transportation, aerospace, and microelectronics.
The materials are also recyclable, which could result in major cost savings for the semiconductor industry, advanced manufacturing or advanced composites for transportation, as it would allow firms to rework high-value but defective manufactured parts or chips instead of throwing them away.
“Although there has been significant work in high-performance materials, today’s engineered polymers still lack several fundamental attributes. New materials innovation is critical to addressing major global challenges, developing new products and emerging disruptive technologies,” said James Hedrick, Advanced Organic Materials Scientist, IBM Research.
“We’re now able to predict how molecules will respond to chemical reactions and build new polymer structures with significant guidance from computation that facilitates accelerated materials discovery. This is unique to IBM and allows us to address the complex needs of advanced materials for applications in transportation, microelectronic or advanced manufacturing.”
The most recent new class of polymer materials was discovered and introduced to the commercial market decades ago and most current polymer research involves combining known polymers or simply adjusting chemical functional groups on known polymers to access desired properties.
In research published today in the journal Science the IBM scientists explain how they used a novel ‘computational chemistry’ hybrid approach to accelerate the materials discovery process that couples lab experimentation with the use of high-performance computing to model new polymer forming reactions.
The new polymers were created at just over room temperature and with very inexpensive starting chemicals. One type of polymer is formed that is stronger than most polymers, but still maintains its flexibility because of solvent that is trapped within the network.
If this material is heated to high temperatures, the polymer becomes even stronger due to a rearrangement of covalent bonds and loss of the solvent that is trapped in the polymer, though this does make it more brittle.
Other polymers constructed using the same technology but instead formed by reacting small, flexible pieces of a polymer, this new material displays very different properties than the ultra-strong polymers.
Instead of being robust, brittle, and strong they form gels with the solvent that they are produced in that are elastic and if they are severed and the pieces are placed back in proximity so they physically touch, the chemical bonds are reformed between the pieces making it a single unit again within seconds.
Both polymers remain intact when they are exposed to basic water (high pH), but selectively decompose when exposed to very acidic water (very low pH). Slightly acidic water does not decompose either material, which means that under the right conditions the polymer can be reverted back to its starting materials enabling it for reuse for other polymers.
The material can also be manufactured to have even higher strength if carbon nanotubes or other reinforcing fillers are mixed into the polymer and are heated to high temperatures to create “composite blends” with properties similar to metal but at a fraction of the weight for use in transportation.