By Josh Perry, Editor
Researchers at the Massachusetts Institute of Technology (MIT) in Cambridge have developed a new lightweight, flexible polymer that can conduct heat 10 times better than most commercially-available polymers and could be a step forward in thermal management applications.
Engineers at MIT have developed a polymer thermal conductor — a plastic material that works as a heat conductor, dissipating heat rather than insulating it. (Chelsea Turner/MIT)
According to an article on the MIT website, the researchers had previously developed thermally conductive polymers by untangling the polymer chains into ultra-thin, ordered chains. That research created one-way paths for heat to travel (down the length of the chain), but the weak Van der Waals forces would not allow heat to travel between the polymer chains.
In the new study, researchers used oxidative chemical vapor deposition (oCVD), which directs two vapors onto a substrate and the interaction creates a film. One of the vapors contained monomers that formed into polymer chains when oxidized onto the silicon/glass substrate.
“The team measured each sample’s thermal conductivity using time-domain thermal reflectance — a technique in which they shoot a laser onto the material to heat up its surface and then monitor the drop in its surface temperature by measuring the material’s reflectance as the heat spreads into the material,” the article explained.
The polymers conducted heat at a rate of 2 W/mK, 20 times faster than conventional polymers. The material was also found to be isotropic and thus expected to conduct heat in all directions, which makes it even more valuable in thermal management.
The research was recently published in Science Advances. The abstract read:
“Traditional polymers are both electrically and thermally insulating. The development of electrically conductive polymers has led to novel applications such as flexible displays, solar cells, and wearable biosensors. As in the case of electrically conductive polymers, the development of polymers with high thermal conductivity would open up a range of applications in next-generation electronic, optoelectronic, and energy devices.
“Current research has so far been limited to engineering polymers either by strong intramolecular interactions, which enable efficient phonon transport along the polymer chains, or by strong intermolecular interactions, which enable efficient phonon transport between the polymer chains.
“However, it has not been possible until now to engineer both interactions simultaneously. We report the first realization of high thermal conductivity in the thin film of a conjugated polymer, poly(3-hexylthiophene), via bottom-up oxidative chemical vapor deposition (oCVD), taking advantage of both strong C=C covalent bonding along the extended polymer chain and strong π-π stacking noncovalent interactions between chains.
“We confirm the presence of both types of interactions by systematic structural characterization, achieving a near–room temperature thermal conductivity of 2.2 W/m·K, which is 10 times higher than that of conventional polymers. With the solvent-free oCVD technique, it is now possible to grow polymer films conformally on a variety of substrates as lightweight, flexible heat conductors that are also electrically insulating and resistant to corrosion.”