  Tailoring the thermal conductivity of polymers is central to enlarge their
applications in the thermal management of flexible integrated circuits.
Progress has been made over the past decade by fabricating materials with
various nanostructures, but a clear relationship between various functional
groups and thermal properties of polymers remains to be established. Here, we
numerically study the thermal conductivity of single-stranded carbon-chain
polymers with multiple substituents of hydrogen atoms through atomic mass
modification. We find that their thermal conductivity can be tuned by atomic
mass modifications as revealed through molecular dynamics simulations. The
simulation results suggest that heavy homogeneous substituents do not assist
heat transport and trace amounts of heavy substituents can in fact hinder heat
transport substantially. Our analysis indicates that carbon chain has the
biggest contribution (over 80%) to the thermal conduction in single-stranded
carbon-chain polymers. We further demonstrate that atomic mass modifications
influence the phonon bands of bonding carbon atoms, and the discrepancies of
phonon bands between carbon atoms are responsible for the remarkable drops in
thermal conductivity and large thermal resistances in carbon chains. Our study
provides fundamental insight into how to tailor the thermal conductivity of
polymers through variable substituents.
