Thermal conductivity enhancement of liquid crystalline epoxy/MgO composites by formation of highly ordered network structure

To develop a high thermal conductive composite, an MgO filler was incorporated into a liquid crystalline (LC) epoxy containing a mesogenic moiety. The thermal conductivity of the obtained composite was 1.41 W/(m?K) at 33 vol% content, which was remarkably higher than the value predicted using Bruggeman's model. To investigate the reason for this significant enhancement of the thermal conductivity in the LC epoxy composites, the LC phase structure of the composite was analyzed by a polarized optical microscope, an X-ray diffractometry (XRD) and a polarized IR mapping measurement. An XRD analysis indicated the local formation of a highly ordered smectic phase structure, even in the high-loading composite. This result indicated the promotion of the self-assembly of the mesogenic network polymer chains by the MgO filler loading. We considered that this highly ordered structural formation can lead to an increase in the matrix resin's thermal conductivity, which can result in the effective enhancement of the thermal conductivity in the LC epoxy/MgO composite.