**Chain length effect on thermal transport in amorphous polymers and a
structure-thermal conductivity relation**

XF Wei and TF Luo, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 21, 15523-15530 (2019).

DOI: 10.1039/c9cp02397f

The physics of thermal transport in polymers is important in many
applications, such as in heat exchangers and electronics packaging. Even
though thermal conductivity models for amorphous polymers have been
reported since the 1970s, none of the published models included the
chain conformation and chain stiffness effects. In this study, we use
molecular dynamics (MD) simulations to study the chain length effect on
thermal conductivity of amorphous polyethylene (PE), and the number of
repeating C2H4 units ranges from 5 to 200. The total thermal
conductivity is decomposed into its contributions from energy convection
(k-convection), and heat transfer through nonbonding (k-nonbonding) and
bonding (k-bonding) interactions. Each part of the contributions is
fitted empirically by using a scaling relationship: k-convection
(Einstein's diffusion coefficient model), k-nonbonding proportional to n
(Choy's model) and k-bonding (from this study), where R-g is the radius
of gyration, n is the number density, and xi is the persistence length.
Summarizing these three components, we emphasize the chain conformation
(R-g) and chain stiffness (xi) effects on thermal conductivity, and we
propose a structure-property relation model for amorphous polymers. Our
empirical model is compared with Hansen's experimental data **D. Hansen,
R. Kantayya and C. Ho, Polym. Eng. Sci., 1966, 6, 260-262** and with our
MD results. Our empirical model relies on realistic structural
properties to enable accurate predictions. We believe that our model has
captured some key structure-property relations in amorphous polymers.

Return to Publications page