Filler surface adsorption of mesogenic epoxy for LC Epoxy/MgO composites with high thermal conductivity

Mesogenic epoxies were adsorbed onto the surface of an MgO filler treated with an amino-silane coupling agent and the epoxy-adsorbed MgO filler was dispersed into the liquid crystalline (LC) epoxy matrix resin to develop a high thermal conductivity composite. The effect on the interfacial interaction and the free volume of the LC epoxy composite was investigated by X-ray photoelectron spectroscopy (XPS), X-ray diffractometry (XRD), and positron annihilation lifetime spectroscopy (PALS). The thermal conductivity of the obtained composite (3.16 W/(m.K)) was remarkably higher than that of the nonadsorbed MgO system (1.93 W/(m.K)) at almost the same content of 44-45 vol%. This significant improvement of the thermal conductivity can be attributed to the highly ordered structural formation that was induced by the pi-pi interaction effect of the mesogenic moieties between the adsorbed epoxies and the matrix resin.