  Despite the desirability of polymers for use in many products due to their
flexibility, light weight, and durability, their status as thermal insulators
has precluded their use in applications where thermal conductors are required.
However, recent results suggest that the thermal conductance of polymers can be
enhanced and that their heat transport behaviors may be highly sensitive to
nanoscale control. Here we use non-equilibrium molecular dynamics (MD)
simulations to study the effect of mechanical twist on the steady-state thermal
conductance across multi-stranded polyethylene wires. We find that a highly
twisted double-helical polyethylene wire can display a thermal conductance up
to three times that of its untwisted form, an effect which can be attributed to
a structural transition in the strands of the double helix. We also find that
in thicker wires composed of many parallel strands, adding just one twist can
increase its thermal conductance by over 30%. However, we find that unlike
stretching a polymer wire, which causes a monotonic increase in thermal
conductance, the effect of twist is highly non-monotonic, and certain amounts
of twist can actually decrease the thermal conductance. Finally, we apply the
Continuous Chirality Measure (CCM) in an attempt to explore the correlation
between heat conductance and chirality. The CCM is found to correlate with
twist as expected, but we attribute the observed heat transport behaviors to
structural factors other than chirality.
