Heat Transfer Organic Materials: Robust Polymer Films with the Outstanding Thermal Conductivity Fabricated by the Photopolymerization of Uniaxially Oriented Reactive Discogens.

Abstract

For the development of advanced heat transfer organic materials (HTOMs) with excellent thermal conductivities, triphenylene-based reactive discogens, 2,3,6,7,10,11-hexakis(but-3-enyloxy)triphenylene (HABET) and 4,4',4″,4‴,4'''',4'''''-(triphenylene-2,3,6,7,10,11-hexaylhexakis(oxy))hexakis(butane-1-thiol) (THBT), were synthesized as discotic liquid crystal (DLC) monomers and cross-linkers, respectively. A temperature-composition phase diagram of HABET-THBT mixtures was first established based on their thermal and microscopic analyses. From the experimental results, it was realized that the thermal conductivity of DLC HTOM was strongly affected by the molecular organizations on a macroscopic length scale. Macroscopic orientation of self-assembled columns in DLC HTOMs was effectively achieved under the rotating magnetic fields and successfully stabilized by the photopolymerization. The DLC HTOM polymer-stabilized at the LC phase exhibited the remarkable thermal conductivity above 1 W/mK. When the DLC HTOM was macroscopically oriented, the thermal conductivity was estimated to be 3 W/mK along the in-plane direction of DLC molecule. The outstanding thermal conductivity of DLC HTOM should be originated not only from the high content of two-dimensional aromatic discogens but also from the macroscopically oriented and self-assembled DLC. The newly developed DLC HTOM with an outstanding thermal conductivity as well as with an excellent mechanical sustainability can be applied as directional heat dissipating materials in electronic and display devices.