  Recently, some reports show that the ultra-low thermal conductivity of bulk
polymers can be enhanced along one direction, which limits its applications.
Here, we proposed paved crosswise laminate methods which can enhance the
thermal conductivity of bulk polyethylene (PE) along two directions. We find
that the thermal conductivity of paved crosswise polyethylene laminate (PPEL)
reaches as high as 181 W/m-K along two in-plane directions, which is three
orders of magnitude larger than bulk amorphous polyethylene and even more than
two times larger than PE single chain (54 W/m-K). The analyses of mechanism
indicated that PPEL is a much more crystal-like structure due to the
inter-chain van der Waals interactions. Our study may provide guides on the
design and fabrication of polymer structures with high thermal conductivity.
