  In this article, we review thermal transport in polymers with different
morphologies from aligned fibers to bulk amorphous states. We survey early and
recent efforts in engineering polymers with high thermal conductivity by
fabricating polymers with large-scale molecular alignments. The experimentally
realized extremely high thermal conductivity of polymer nanofibers are
highlighted, and understanding of thermal transport physics from molecular
simulations are discussed. We then transition to the discussion of bulk
amorphous polymers with an emphasize on the physics of thermal transport and
its relation with the conformation of molecular chains in polymers. We also
discuss the current understanding of how the chemistry of polymers would
influence thermal transport in amorphous polymers and some limited, but
important chemistry-structural-property relationships. Lastly, challenges,
perspectives and outlook of this field are presented. We hope this review will
inspire more fundamental and applied research in the polymer thermal transport
field to advance scientific understanding and engineering applications.
