Plastic as a heat conductor

Chelsea Turner/MIT

A PLASTIC has been developed that can dissipate heat instead of trapping it, which could be used to stop electronic devices overheating.

Plastics are excellent insulators but trapping heat can be a problem for devices such as laptops and mobiles. Creating plastics that can transport heat has so far been a challenge. Polymers trap heat because they are made of long chains of disordered monomers which also have weak molecular interactions. Previous work on creating heat-conducting polymers used either intramolecular forces, which enable heat transport along chains, or intermolecular forces, which enable transport between chains. These conventional approaches have scalability challenges or are limited to heat transport in one direction.

A team of engineers at MIT and Argonne National Laboratory has devised a method that uses both intramolecular and intermolecular forces to create a polymer that can transport heat in all directions.

“Traditional polymers are both electrically and thermally insulating,” said Yanfei Xu, from MIT’s department of mechanical engineering. “Our polymer can thermally conduct and remove heat much more efficiently. We believe polymers could be made into next-generation heat conductors for advanced thermal management applications, such as a self-cooling alternative to existing electronics casings.”

They used oxidative chemical vapour deposition (oCVD), which directs two vapours (an oxidant and a vapour of monomers) into a chamber which then interact and form a film on a substrate. This method allows the coating of complex geometries and can be used to coat almost any type of surface.

“We grew the polymers on silicon/glass substrates, onto which the oxidant and monomers are adsorbed and reacted, leveraging the unique self-templated growth mechanism of CVD technology," said Xiaoxue Wang from MIT’s department of chemical engineering.

They tested the conductivity of the samples by shooting a laser at the material to heat it up and then monitoring how the temperature dropped over time. The samples were able to conduct heat at 2 W/mK, which is ten times faster than conventional polymers. The heat was conducted uniformly, showing that the material can conduct heat in all directions, which increases its heat-dissipating abilities.

“We can directly and conformally coat this material onto silicon wafers and different electronic devices,” said Xu. “If we can understand how thermal transport [works] in these disordered structures, maybe we can also push for higher thermal conductivity. Then we can help to resolve this widespread overheating problem, and provide better thermal management.”

Science Advances http://doi.org/cnjd