Domain segregation of polymer blends or block copolymers in the presence of thermal conducting high aspect ratio nanocrystals leads to preferential placement of conductive filler either inside one domain, which promote the self-assembly of a thermal and/or electrical conducting pathway composed of high aspect ratio filler. The self-assembly of such thermal and/or electrical conducting pathway effectively enhances the thermal and/or electrical conductivity of the composite with significantly less amount of filler.