New class of industrial polymers ideal for electronics

19 May 2014

IBM scientists created a family of materials that are stronger than bone, self-healing and solvent-resistant while being completely recyclable.

Scientists from IBM Research have successfully demonstrated a new class of polymer materials that can potentially transform manufacturing and fabrication in the fields of transportation, aerospace, and microelectronics.

Through the unique approach of combining high performance computing with synthetic polymer chemistry, the scientists discovered a new class of polymers that are resistant to cracking, stronger than bone, can reform to its original shape (self-heal), and completely recyclable. Also, these materials can be transformed into new polymer structures to further bolster their strength by 50% - making them ultra strong and lightweight. This could impact almost every industry looking to innovate across engineering, product design and spur new technologies.

Polymers, a long chain of molecules that are connected through chemical bonds, are an indispensable part of everyday life. They are a core material in common items ranging from clothing and drink bottles (polyesters), paints (polyacrylics), plastic milk bottles (polyethylene), secure food packaging (polyolefins, polystyrene) to major parts of cars and planes (epoxies, polyamides and polyimides). They are also essential components in virtually every emerging advanced technology dating back to the industrial revolution – the steam engine, the space ship, the computer, the mobile phone.

However, today’s polymer materials are limited in some ways. In transportation and aerospace, structural components or composites are exposed to many environmental factors (de-icing of planes, exposure to fuels, cleaning products, etc.) and bear poor environmental stress crack resistance (i.e., catastrophic failure upon exposure to a solvent). Also, these polymers are difficult to recycle because they cannot be remolded or reworked once cured or thermally decomposed upon heating to high temperatures. As a result, these end up in the landfill together with toxins such as plasticizers, fillers, and color additives which are not biodegradable.

IBM’s discovery of a new family of materials with a range of tunable and desirable properties provides a new opportunity for exploratory research and applications development to academia, materials manufacturers and end users of high performance materials.  Two new related classes of materials have been discovered which possess a very distinctive range of properties that include high stiffness, solvent resistance, the ability to heal themselves once a crack is introduced and can be used as a resin for filled composite materials to further bolster its strength.  

Also, the ability to selectively recycle a structural component would have significant impact in the semiconductor industry, advanced manufacturing or advanced composites for transportation, as one would be able to rework high-value but defective manufactured parts or chips instead of throwing them away. This would bolster fabrication yields, save money and significantly decrease microelectronic waste.

This research was published today in the peer-reviewed journal, Science.

These polymers, formed through a condensation reaction where molecules join together and lose small molecules as by-products such as water or alcohol, were created in an operationally simple procedure and are incredibly tunable.

At low temperatures (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 (now stronger than bone and fiberboard), but as a consequence is more brittle (similar to how glass shatters).

Additionally, 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 previously discussed. Instead of being robust, brittle, and strong, they form gels with the solvent that they are produced in that are elastic (in other words, they stretch like a rubber band).

Probably the most unexpected and remarkable characteristic of these gels is that 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. This type of polymer is called a "self healing" polymer because of its ability to do this and is made possible here due to hydrogen-bonding interactions in the hemiaminal polymer network. One could envision using these types of materials as adhesives or mixing in with other polymers to induce self-healing properties in the polymer mixture. Furthermore, these polymers are reversible constructs which means that can be recycled in neutral water, and that they might find use in applications that require reversible assemblies, such as drug cargo delivery.

Remarkably, 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. This means that under the right conditions, the polymer can be reverted back to its starting materials, which enables 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. This process enables polymers to have properties similar to metals which is why these “composite blends” are used for manufacturing in airplane and cars. An advantage to using polymers in this case over metals is that they are more lightweight, which in the transportation industry translates to savings in fuel costs.

Contact Details and Archive...

Print this page | E-mail this page